Tutorial Guide AutoGrid 82 1 Advanced-Acrov5

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Advanced Tutorials

AutoGrid™ v8

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-Advanced Tutorials

AutoGrid™ v8.c

Documentation v8.c

NUMECA International

5, Avenue Franklin Roosevelt

1050 Brussels

Belgium

Tel: +32 2 647.83.11

Fax: +32 2 647.93.98

Web: http://www.numeca.com

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TABLE OF CONTENT

INTRODUCTION

TUTORIAL 1: Meridional Effect

1-1 INTRODUCTION 1-1 1-1.1 Introduction 1-1 1-1.2 Prerequisites 1-2 1-1.3 Problem Description 1-2 1-1.4 Preparation 1-2 1-2 MESH GENERATION 1-4

1-2.1 Create Mesh Project 1-4

1-2.2 Load Geometry & Define Main Properties 1-4

1-2.3 Set Default Topology 1-7

1-2.4 Meridional Control 1-9

1-2.5 Blade-to-Blade Control 1-11

1-2.6 Meridional Effect Generation 1-14

1-2.7 3D Mesh Generation 1-22

1-2.8 3D Mesh Visualization 1-23

1-2.9 Check Boundary Conditions & Mesh Quality 1-23

1-2.10 Save Project 1-26

1-2.11 Periodic Full Non Matching Connection 1-26

1-2.12 Full Matching Connection 1-28

TUTORIAL 2: Non-Axisymmetric Hub/Shroud

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TUTORIAL 3: Bypass Configuration

TUTORIAL 4: Tandem Row

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TUTORIAL 5: Cascade Configuration

TUTORIAL 6: Fin on Fan

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TUTORIAL 7: 3D Technological Effect - Casing Treatment

7-2.1 Open Existing Mesh Project 7-4

7-2.2 Adapt Mesh Project 7-4

7-2.3 3D Technological Effect Generation 7-7

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What’s in This Guide ?

This Tutorial Guide contains a number of advanced tutorials driving the user in AutoGrid™ v8 to mesh different internal turbomachinery configurations. In each tutorial, specific features related to mesh generation are demonstrated.

Advanced Tutorials are detailed tutorials designed to introduce specific features available within AutoGrid™ v8. These tutorials provide explicit instructions for all steps of the mesh generation process. Advanced Tutorials do require as pre-requisite the knowledge of the mesh generation proc-ess presented in basic tutorials 1 to 7, and can be treated separately, in any order. They addrproc-ess dif-ferent types of features available on both axial and centrifugal compressors, pumps and turbines.

Where to Find the Files Used in the Tutorials ?

Each of the mesh generation starts from an existing geometry. The appropriate files (and any other relevant files used in the tutorial) are stored on AutoGrid™ v8 DVD-ROM, more precisely in the /

DOC/_Tutorials/AutoGrid/_advanced directory.

How to Use this Guide ?

Depending upon your familiarity with computational fluid dynamics and your interest in some par-ticular configuration, you can use this tutorial guide in a variety of ways.

For the Beginner

If you are beginning user of AutoGrid™, you should first read and solve basic tutorials 1 to 7, in order to familiarize yourself with the interface and basis of the mesh generation technique. You may then want to concentrate on a advanced tutorial that demonstrates features that you are going to resolve. For example, if you are planning to mesh a seal leakage, you should look at Advanced Tutorial 1.

For the Experienced User

If you are an experienced user of AutoGrid™, you can read and/or solve the advanced tutorial(s) that demonstrate features that you are going to resolve. For example, if you plan to mesh a turboma-chine presenting a non-axisymmetric hub, you should look at Advanced Tutorial 2.

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Conventions Used in this Guide

Several conventions are used in the tutorials to facilitate your learning process.

Following a short introduction, each tutorial is divided into sections respectively related to the mesh generation steps from the geometry definition to the 3D mesh generation.

Inputs required to execute the tutorials are restricted to the geometry, either in a ".geomTurbo" or CAD related format.

The sequence of actions to be executed are described through a step-by-step approach, in the form of arabic numbers.

Additional insight about some specific actions and/or features is frequently added to illustrate the tutorial further. This information is proposed for the purpose of clarity and completeness, and should not be executed. It appears in italicized type.

Contact NUMECA support team at +32-2-647.83.11 or send an e-mail to [email protected] for any question or information you may require. To allow NUMECA support to help you out within the shortest delays, please provide a detailed description of the observed behaviour and performed analysis.

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TUTORIAL 1:

Meridional Effect

1-1

Introduction

1-1.1

Introduction

The resolution of computational fluid dynamics (CFD) problems involves three main steps:

•

spatial discretization of the flow equations

•

flow computation

•

visualization of the results

To answer these questions, NUMECA has developed a Flow INtegrated Environment for internal and Turbomachinery assimilations. Called FINE™/Turbo, the environment integrates the following tools:

•

IGG™ is an Interactive Geometry modeler and Grid generator software, based on structured multi-block techniques

•

AutoGrid™ is a three-dimensional Automated Grid generation software, dedicated to turboma-chinery applications. Similarly to IGG™, it is based on structured multi-block techniques

•

Euranus is a state-of-the-art multi-block flow solver, able to simulate Euler and Navier-Stokes equations in the laminar, transitional and turbulent regimes

•

CFView™ is a highly interactive flow visualization and post-treatment software

•

FINE™ Graphical User Interface is a user-friendly environment that includes the different soft-wares. It integrates the concept of projects and allows the user to achieve complete simulations, going from the grid generation to the flow visualization, without the need of file manipulation A turbomachine is a device in which the energy is transferred either to or from a continuously flow-ing fluid by the dynamic action of one or more movflow-ing blade rows. It plays a major role in particu-lar in aircraft, marine space (liquid rockets), land propulsion system but also in hydraulic, gas and steam turbines applications. It is also involved in industrial pipeline and processing equipment such as gas, petroleum and water pumping plants. Other applications can be related to heart-assist pumps, industrial compressors and refrigeration plants, among others.

The turbomachinery field includes turbines, pumps, fans, compressors. A turbomachine is com-posed of several basic elements including the blade (also called vane if it is non-rotating), hub, and shroud. Several technological effects involving clearances, seal leakages and cooling holes among

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Meridional Effect

Introduction

others can complete the machine. Due to the complexity of the blade shapes, the presence of tech-nological elements and the rotation of machine, the nature of the flow is strongly three-dimensional, often depicting complex flow paths.

This tutorial is particularly adapted to the mesh generation of seal leakages in turbomachinery

applications. It makes exclusive use of AutoGrid™ v8 and describes the main actions required to

mesh the configuration of interest. In this tutorial you will learn how to:

•

Read an existing geometrical file into AutoGrid™ v8;

•

Control meridional flow paths and blade-to-blade mesh;

•

Generate and control the mesh in the seal leakage;

•

Control the quality of the mesh in the blade-to-blade and 3D mesh.

1-1.2

Prerequisites

This tutorial does not require any particular prerequisite but it is strongly recommended for begin-ners to perform the basic tutorials 1 to 7.

1-1.3

Problem Description

The problem to be considered is shown schematically here below (meridional view). The project consists in the mesh generation of a seal leakage on the top of the Aachen turbine rotor treated as an isolated axial-flow wheel.

1-1.4

Preparation

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Copy the files located in cdrom:\DOC\_Tutorials\AutoGrid\_advanced\Tutorial_1 to your working directory, where cdrom must be replaced by the name of your DVD-ROM.

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Start AutoGrid™ v8.x

For LINUX and UNIX systems, you can access AutoGrid™ v8.x graphical user interface with the following command line

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Introduction

Meridional Effect

For WINDOWS systems, you can access AutoGrid™ v8.x graphical user interface from the start menu going to /Programs/NUMECA software/fine8x/IGG or /Programs/NUMECA software/autogrid8x/IGG

•

Access the menu Modules, select AutoGrid and confirm "yes" to enter AutoGrid™ v8. You’re now ready to start the grid generation process and mesh the configuration presenting a seal leak-age!

AutoGrid™ v8 graphical user interface includes several windows that allow to visualize the geom-etry and mesh of the turbomachine simultaneously in the meridional, blade-to-blade and 3D view. The access to main menu and controls is proposed through a menu bar and a quick access pad, and is completed with a tool/icon bar. The execution of the different actions undertaken is summarized in the message box at the bottom of the interface.

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Meridional Effect

Mesh Generation

1-2

Mesh Generation

A step by step approach is proposed in the following lines. It aims at driving you through the vari-ous steps that need to be executed from the creation of the mesh project to the validation of the final mesh quality.

1-2.1

Create Mesh Project

1. Close the Open Turbo Project Wizard dialog box

2. Go to menu File -> New Project

3. Click yes to close the active project

4. Choose the icon Start a New Project From Scratch

The Open Turbo Project Wizard dialog box enables the user to retrieve a ".trb" file (with associated grid) including the data required to regenerate a mesh on an identical or similar geometry. In this tutorial, these data will be progressively introduced based on the geometry of the project case.

1-2.2

Load Geometry & Define Main Properties

5. Click-left row1 in Rows Definition row 1 in the Quick Access Pad (QAP) to activate

the current row

6. Click-left in the meridional view

7. Go to Geometry Definition Import and Link CAD Graphic window opens, allowing geometry import.

8. Click-left on File Open...

9. Select geometry.dat file from the file chooser

10.Define the hub curve

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Click-left on the hub as it turns to yellow

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Click-right and select Link to Hub

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Mesh Generation

Meridional Effect

11.Define the shroud curve

•

Click-left on the shroud as it turns to yellow

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Click-right and select Link to Shroud

Shroud curve is displayed in the meridional view.

12.Define the blade

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Click-left row1 in Rows Definition row 1 in the Quick Access Pad (QAP) to activate

the current row, if not done already

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Go to Geometry Select Surfaces A message will prompt to select surfaces.

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Type key binding <a> twice to select all surfaces (they turn to red or yellow)

The binding key <a> acts as a toggle, activating or de-activating all surfaces. The View/View Solid menu acts as a toggle and allows to visualize the sur-faces that are active.

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Click-right twice to quit surfaces selection and select Link to Blade

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Meridional Effect

Mesh Generation

13.Define leading edge and trailing edge

•

Click-left at blade leading edge line definition, inside the Import CAD window

•

As it turns yellow, click-right and select Link to Leading Edge

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Click-left at blade trailing edge line definition, inside the Import CAD window

•

As it turns yellow, click-right and select Link to Trailing Edge

Leading and trailing edges are displayed in the meridional view.

When blade intersects hub and shroud, inlet and outlet are displayed in the meridional view.

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Mesh Generation

Meridional Effect

14.Go to File -> Exit

15.Click-left on Rows Definition row 1 to activate row1

16.Click-right on row 1 to get the contextual menu and select Properties

17.Enter the Periodicity (number of blades). Left-click inside the string input area and type <41>, press <Enter> to confirm

18.Enter <-3500> in Rotation Speed (rpm)

This speed will be transferred to FINE™ graphical user interface and ease the input of boundary conditions later on.

The sign of the rotational speed is positive (+) when the blade row is rotating in the positive θ direction, and negative otherwise.

19.Select Rotor as a row type and Axial as a row orientation

The row type and row orientation settings are only information that will not impact or control the mesh generation process.

20.Close the dialog box

1-2.3

Set Default Topology

21.Click-left on Rows Definition -> row 1 to activate the row, if not done already

22.Select Grid Level/Medium through Mesh Control in Quick Access Pad

23.Estimate the width of the first cell at the wall:

The width of the first cell close to the wall must be selected with care since the quality of the flow solution will often depend upon the capture of the flow phe-nomena inside the boundary layers which develop along the solid walls. Depending upon the turbulence model selected, NUMECA recommends to locate the nearest grid point along the wall, at a distance that corresponds to

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Meridional Effect

Mesh Generation

parietal coordinate y+ ranging from 1-5 (low Reynolds number models) or 30-50 (high Reynolds number models). Assuming thermal effects must be mod-elled accurately, y+ can reach values as low as 0.1.

The relation between the parietal coordinate y+ and width of the first cell close to the wall y is driven by the Blasius equation, expressed as follows for turbulent flows:

where:

- y_wall is the distance of the nearest grid point to the wall (in meter);

- V_ref is a reference velocity of the flow, for instance the inlet velocity (in m/s); - υ is the kinematic viscosity of the fluid (in m2/s), i.e. the dynamic viscosity divided by the density;

- L_ref is a reference length of the test case (in meter); - y+ is a non-dimensional value.

In the present case, one can estimate that V_ref=30 m/s; L_ref=0.3m; υ=1.038e-5 m2/s Assum-ing one wishes to get y+ =1 at the wall, it comes that y = 1 x 10-5 m. Input the value of the

Cell Width = <1e-5> <Enter> in Row Mesh Control.

24.Select (Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology

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Mesh Generation

Meridional Effect

The default skin-topology includes 5 blocks as follows: - the skin block is a O-mesh surrounding the blade

- the inlet block is a H-mesh located upstream the leading edge - the outlet block is a H-mesh located downstream the trailing edge - the up block is a H-mesh located above the blade section

- the down block is a H-mesh located under the blade section

1-2.4

Meridional Control

25.Move inlet and outlet locations

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Click-right on inlet curve when highlighted in yellow in the meridional view

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Select Properties

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Select Linear - Z constant, type <0.02>, press <Enter> to confirm

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Click-right on outlet curve when highlighted in yellow in meridional view

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Select Properties

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Select Linear - Z constant, type <0.16>, press <Enter> to confirm skin block

down block outlet block

up block

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Meridional Effect

Mesh Generation

The new inlet and outlet locations are displayed in the meridional view.

You can access the control points of the inlet/outlet line and modify their loca-tion by dragging the points. The exact coordinates of the control points can also be introduced with click-right on the control point; a dialog box appears, enabling the user to enter the point coordinates in (rz) mode.

You can access the properties of the inlet/outlet line by click-right on control line when highlighted and selecting "Properties". The dialog box is divided in two main parts. The first part allows to specify the reference frame. When it is set to "Relative", the control points are relative to a row and their reference depends on the position of the control line. Either the control points are rela-tive to the row inlet and its blade leading edge, either to the leading and trail-ing edge, or to the blade trailtrail-ing edge and the row outlet. The second part of the dialog box allows to control the properties of the meridional control line namely the shape, the cell width, the streamwise index and the number of points in streamwise direction.

26.Select (Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology based on the new inlet/outlet locations

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Mesh Generation

Meridional Effect

27.Go to QAP Mesh Control

28.Modify the number of flow path as <33> <Enter>

29.Control flow paths if necessary through Mesh Control -> Row Mesh Control -> Flow

Paths Control

The Expert section allows the user to control the visualization, the shape and the parameters related to flow path smoothing. The meaning of these parame-ters is detailed in the user manual.

The Manual Edition mode allows the user to control directly the block faces which are used to construct flow paths. Edges can be moved, segments can be created or modified and grid points distribution on segments can be control-led. More details can be found in the user manual.

30.Keep data identical

31.Click on Generate

1-2.5

Blade-to-Blade Control

33.Click on Generate B2B

34.Go to

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Meridional Effect

Mesh Generation

By default, non-matching connections are applied at periodic boundaries. Matching connections at periodic boundaries can be obtained by activating the Matching Periodicity check button. Press Re(set) Default Topology to re-generate the mesh in the blade-to-blade plane.

In most cases, the presence of non-matching connections somehow improves the orthogonality in the overall mesh. This is especially true in highly stag-gered configurations.

35.Keep Matching Periodicity deactivated and all other data identical

In several turbomachinery types, the blades are highly staggered (Automatic

High Staggered Blade Detection within AutoGrid™). If the solid angle at the inlet (outlet) of the machine becomes greater than 450_{and if the location of}

the inlet (outlet) limits of the domain is close to the leading edge (trailing edge) of the blades, then the default topology is not suitable anymore since the cells located near the inlet (outlet) boundary become very skewed. To improve this unexpected behaviour, AutoGrid™ uses the High Staggered Blade

Opti-mization.

36.Deactivate Topology option

37.Go to Mesh Control Row Mesh Control B2B Mesh Topology Control -> Grid Points to control the number of grid points in the blade-to-blade view

38.Click-left on the number of nodes, make the proper modification in the entry box and press <Enter> to confirm the modification

The number of points specified is recommended to be 4xn + 1 (where n is an

integer) to allow multigrid process on minimum 3 grid levels within FINE™.

39.Visualize the result in blade-to-blade view after selecting Generate B2B to regenerate the flow paths and the mesh in blade-to-blade plane.

40.Deactivate Grid Points option

41.Close the dialog box.

42.Go to Mesh Control-> Active B2B Layer to specify the flow path (layer) on which the blade-to-blade mesh will be plotted in the blade-to-blade view

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Mesh Generation

Meridional Effect

By default, the active layer is the hub of the machine (Active Layer (%span) set to 0). The layer selected for visualization is defined in percentage of span, going from hub (0%) to shroud (100%).

43.Enter for example <50> <Enter> in order to visualize the mesh at 50% span

44.Select Generate B2B to regenerate the blade-to-blade mesh on new specified layer in the blade-to-blade view

Detailed analysis of mesh quality can be performed on Blade-to-Blade mesh after generation. Information on orthogonality, aspect ratio and expansion ratio can be outlined in this window using the Type pull-down menu and plot-ted in the blade-to-blade view on active layer selecplot-ted in Mesh Control/ Active B2B Layer.

45.Check for grid quality by clicking on

46.Select quality criteria using the Type pull-down menu

47.Click-left on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn for each row

48.Click-left on part of the histogram to plot the concerned cells in blade-to-blade view

49.Click-left on More info button to obtain information about minimum and maximum values of the selected criteria

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Meridional Effect

Mesh Generation

51.Go to Mesh Control -> Row Mesh Control -> Optimization Control to adapt the mesh optimization parameters if necessary to enhance the quality of the mesh

Optimization is performed in the form of smoothing and is executed on each layer using multi-block elliptic techniques. The number of Optimization Steps represents the number of iterations performed with the elliptic smoother. By default, 100 iterations are applied.

52.Keep default Optimization Steps and all other data identical

1-2.6

Meridional Effect Generation

1-2.6.1

Configuration Control

54.Click-left on Rows Definition -> row 1 in the Quick Access Pad (QAP) to active the current row, if not done already

55.Click on the button Add ZR Effect to add a meridional effect in the configuration

1-2.6.2

Geometry Definition

56.Click-left on Rows Definition -> zr techno effect 1 in the Quick Access Pad (QAP) if not active already

57.Go to Geometry Definition Import and Link CAD Graphic window opens, allowing geometry import.

58.Select the curves defining the active meridional effect

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Mesh Generation

Meridional Effect

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Click-right and select Import Meridional

Curves defining the meridional effect are displayed in the meridional view.

Curves defining the meridional effects are specified in the ".geomTurbo" file using the basic curve format (see User Manual for more details).

AutoGrid™ provides also geometrical features used to create the solid body of meridional effects interactively. New polylines and C-splines can be created using respectively the Geometry Control subpad and the Geometry menu in the meridional effect edition mode and the steps needed to create these polylines are stored in the ".trb" template file.

59.Click-left on Rows Definition -> zr techno effect 1 in the Quick Access Pad (QAP) if not active already

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Meridional Effect

Mesh Generation

60.Click-right on zr techno effect 1 to get the contextual menu and select Edit to access the meridional effect edition mode

When the meridional effect has several connections with the main blade chan-nel, i.e. a seal leakage have a connection upstream the blade and a connection downstream the blade. In this case the mesh created inside the domain of the effect is divided into two part: one starting from the inlet and one starting from the outlet. At the middle part of the seal leakage, a separation line "rotor-stator" must be defined indicating the location of the division. At this line, defined in the edition mode, the two part of the mesh will be connected by a periodic connection if the connections with the main blade channel are related to the same row or a rotor/stator interface if the connections with the main blade channel are related to different rows.

61.Click on Rotor-Stator Polyline in Geometry Control subpad to create a separation line

62.Click-left on location (yellow spot on existing curve) where the "rotor-stator" polyline will start

63.Click-left on location (yellow spot on existing curve) where the "rotor-stator" polyline will end

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Mesh Generation

Meridional Effect

No curves have to be added at the connection between the blade channel (hub or shroud) and the meridional effect. Automatically the hub and shroud curves will be used as limit of the meridional effect.

1-2.6.3

Topology Control

The domain defining a technological effect must be filled by several structured 2D blocks. The block edges are mapped on the geometry. The Topology

Con-trol subpad provides the tools to create and conCon-trol the blocks

65.Click-left on Insert New Block icon in the Topology Control subpad to start to fill the geometry

66.Click-left to locate the first corner of the 2D block (yellow spot when attracted on existing curve)

67.Click-left to locate the opposite corner of the 2D block

68.Click-left to create the 2D block

69.Click-left on vertex (when highlighted in yellow) of the 2D block to move it when neces-sary

70.Click-left to fix the new position of the vertex on the geometry

71.Repeat steps 69 and 70 for all vertices defining the 2D block

The tool Detect Unmapped Edges in the Topology Default subpad allows to detect if the 2D blocks are well mapping the geometry. In addition, when the

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Meridional Effect

Mesh Generation

vertex is highlighted, the curve on which it is mapped is mentioned in the info area at the bottom of the GUI.

72.Repeat steps 65 to 71 in order to fill the geometry defining the meridional effect while respecting the following rules:

•

the 2D blocks inserted in the meridional effect have to present edges fully and not partly connected to another block edge when connected

•

when the edge mapping is not performed as required, a vertex needs to be inserted

•

a block connection must be established on the separation lines and the mapping of vertices respected (no orphan vertices)

CORRECT

WRONG

Undesired M apping CORRECT separation line WRONG separation line CORRECT

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Mesh Generation

Meridional Effect

•

the 2D blocks should be connected to the rotor/stator polyline with a complete face

•

the 2D blocks should be connected to the shroud or hub with only one face

The blocks can be deleted by click-left on the icon .

73.Click on Detect Unmapped Edges in the Topology Default subpad to control that all the blocks are well mapped

separation line CORRECT separation line WRONG

WRONG

CORRECT

SHROUD SHROUD

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Meridional Effect

Mesh Generation

The tool Detect Unmapped Edges in the Topology Default subpad allows to highlight in green the edges that are not well mapped.

74.Click-right to quit the Detect Unmapped Edges tool

1-2.6.4

Mesh Control

The Topology Default subpad provides the tools to control the mesh of all the blocks filling the technological effect.

75.Keep the Cell Width = <1e-5> <Enter> (as the cell width imposed at step 23) and all other data identical

76.Deactivate Periodic Full Non Matching

The Optimization Steps represents the number of iterations performed with the elliptic smoother.

The Radial Expansion and Far Field Smoothing Steps are used for external cases as propeller or wind turbine applications.

The Maximum Expansion Ratio and Cst Cells Percentage control the mesh that will be generated when using Default Topology.

The Coarse Grid Level control the number of grid levels that will be available within FINE™. A minimum of 3 is recommended.

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Mesh Generation

Meridional Effect

77.Click on Default Topology in the Topology Default subpad to generate the mesh into the meridional effect (seal leakage)

If desired, the default topology can be modified by the user. When click-right on any edge, a popup menu allows to impose the number of points and the point distribution.

78.Click on Detect Channel FNMB Connection in the Topology Default subpad to visualize the connections between the meridional effect and the channel

79.Click-right to quit the Detect Channel FNMB Connection tool

80.Click on Close Edition Mode

separation line

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Meridional Effect

Mesh Generation

All the actions performed during an editing session are stored in the template file (".trb") and can be replayed on similar geometries.

1-2.7

3D Mesh Generation

81.Click-left on Rows Definition -> row 1 and zr techno effect 1 in the Quick Access Pad (QAP) to active the current row, if not done already

82.Click on the icon Generate 3D and confirm the generation

Once 3D grid generation is completed, grid quality is performed and dis-played. Minimum cells skewness, the maximum expansion ratio and aspect ratio are reported, among others. Data are available for the entire mesh sepa-rately for every entity (row, technological effect, bulb). Data related to grid quality report are automatically stored in a report file, once the project file is saved.

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Mesh Generation

Meridional Effect

1-2.8

3D Mesh Visualization

85.Click-right on row 1 and select Properties to activate Default in order to plot the full tur-bomachine

86.Click-right on row 1 and select Toggle 3D View to access the shaded blades in 3D view

87.Click-left in 3D view; the Quick Access Pad (QAP) is modified

88.Click-right to get the contextual menu and activate Full View

89. Use View menu in QAP or View/Patch Viewer... menu to toggle edge or mesh

1-2.9

Check Boundary Conditions & Mesh Quality

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Meridional Effect

Mesh Generation

90.Check for boundary conditions by clicking on

91.Select UND under Type pull-down menu and check that no patches are in the patch list still set with an undefined type

It is important to make sure that no undefined patches (UND) are present in the mesh. In that case, these can usually be removed by increasing the toler-ance and launching the Search procedure.

92.Select Full Non Matching/Define... to visualize the FNMB that are automatically created between the seal leakage (meridional effect) and the shroud of the channel

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Mesh Generation

Meridional Effect

94.Check for negative cells by clicking on

95.Click on Apply

The computation of the negative volumes is performed first. Negative cells can be outlined in the mesh pushing View neg cells button. Beware that the visual-ization of negative cells can be memory consuming when a large number of cells must be displayed. It is then advised to first check the number of negative cells by pressing the Apply button.

It is mandatory to remove all negative cells before the calculation can be started.

96.Check for grid quality by clicking on

Detailed analysis of mesh quality on 3D mesh (in blocks, at boundaries and at FNMB) can be performed only once the 3D mesh has been generated. Infor-mation on orthogonality, angular deviation, aspect ratio, expansion ratio and cell width can be outlined in this window using the Type pull-down menu.

97.Select quality criteria using the Type pull-down menu

98.Click-left on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn per block (0 = all blocks)

99.Click-left on part of the histogram to plot the concerned cells in the 3D view

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Meridional Effect

Mesh Generation

100.Click-left on More info button to obtain information about minimum and maximum val-ues of the selected criteria

1-2.10 Save Project

102. Go to File -> Save Project As <tutorial1> <Enter> to save mesh and template files The mesh files (7 files) contain the multiblock mesh topology, geometry and grid points and the boundary condition types: ".bcs", ".cgns", ".geom" (".xmt_txt"), ".igg", ".config" and ".qualityReport".The meaning of these files is detailed in the user manual.

The template files (4 files) contain the parameters and the geometry needed to reproduced the mesh with AutoGrid™: ".geomTurbo" (".geom-Turbo.xmt_txt"), ".trb" and ".info". The meaning of these files is detailed in the user manual.

1-2.11 Periodic Full Non Matching Connection

AutoGrid™ allows to define a straight meridional effect (periodic boundaries of meridional effect at constant θ) by introducing periodic full non matching connection with repetition between the meridional effect and the channel. In most cases, this capability improves the orthogonality in the overall mesh. This is especially true in highly staggered configurations.

103.Click-left on Rows Definition -> zr techno effect 1 in the Quick Access Pad (QAP) if not active already

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Mesh Generation

Meridional Effect

105.Activate Periodic Full Non Matching

108.Click on the icon Generate 3D and confirm the generation

109. Go to File -> Save Project As <tutorial1_per> <Enter> to save mesh and template

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Meridional Effect

Mesh Generation

1-2.12 Full Matching Connection

AutoGrid™ allows to define a full matching connection between the meridi-onal effect and the channel by adding fixed control lines into the channel. This capability required in most cases more points in the mesh and an orthogonal-ity that will not be improved in the overall mesh. This is especially true in highly staggered configurations.

110.Select meridional view by click-left on it to active the view, if not done already

111.Select Mesh Control -> Row Mesh Control -> Add Z Constant Line to add z-constant lines to map the meridional effect

112.Click-left on shroud in the meridional view to add a z-constant line

113.Repeat step 112 three times to map all the limits of the connections of the meridional effect with the channel

114.Click-right to quit the menu related to the creation of z-constant line

You can access the control points of the z-constant line and modify their loca-tion by click-left and dragging the points. The exact coordinates of the control points can also be introduced with click-right on the control point; a dialog box appears, enabling the user to enter the point coordinates in (rz) mode. You can access the properties of the z-constant line by click-right on control line when highlighted and selecting "Properties". The dialog box is divided in two main parts. The first part allows to specify the reference frame. When it is set to "Relative", the control points are relative to a row and their reference depends on the position of the control line. Either the control points are rela-tive to the row inlet and its blade leading edge, either to the leading and trail-ing edge, or to the blade trailtrail-ing edge and the row outlet. The second part of

Click Left

Ctrl Line 1 Ctrl Line 1

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Mesh Generation

Meridional Effect

the dialog box allows to control the properties of the meridional control line namely the shape, the cell width, the streamwise index and the number of points in streamwise direction.

115.Click-right on first control line when highlighted in yellow

116. Select Properties

117.Activate Linear

118.Set the cell width to <1e-5><Enter>

119.Click-left on the three control lines and apply steps 117 and 118

120.Close dialog box

122.Select (Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology considering the four new control lines

In the blade-to-blade view, additional H-blocks are appearing.Furhermore, in some cases, the default topology may change from normal to high staggered (in this case the blade is high staggered at trailing edge).

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Meridional Effect

Mesh Generation

In the edition mode of the meridional effect, the type connection can be con-trolled.

125.Click on Detect Channel Matching Connection in the Topology Default subpad to visu-alize the connections between the meridional effect and the channel

126.Click-right to quit the Detect Channel Matching Connection tool

An additional control line needs to be added to define both matching connec-tions because the connection of the meridional effect with the channel close to the trailing edge is defined by two blocks.

127.Click on Solid Polyline in Geometry Control subpad to create a separation line

128.Click-left on location (yellow spot on existing curve) where the "solid" polyline will start (at the connection between the two blocks)

Ctrl Line 3

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Mesh Generation

Meridional Effect

129.Click-left on location (yellow spot on existing curve) where the "solid" polyline will end (anywhere in the channel)

This new solid polyline will allow the mapping of the new control line.

130.Click-right to quit

132.Select meridional view by click-left on it to active the view, if not done already

133.Select Mesh Control -> Row Mesh Control -> Add Z Constant Line to add z-con-stant lines to map the meridional effect

134.Click-left on shroud in the meridional view to add a z-constant line at the connection with the channel close to the trailing edge (mapping on the new solid polyline)

135.Click-right on last control line when highlighted in yellow

136.Select Properties

137.Activate Linear

138.Set the cell width to <1e-5><Enter>

Click Left

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Meridional Effect

Mesh Generation

139.Close dialog box

141.Select (Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology considering the four new control lines

In the blade-to-blade view, one additional H-block is appearing between con-trol lines 3 and 5.

In the edition mode of the meridional effect, the type connection can be con-trolled.

144.Click on Detect Channel Matching Connection in the Topology Default subpad to visu-alize the connections between the meridional effect and the channel

Ctrl Line 3 Ctrl Line 4 Ctrl Line 5

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Mesh Generation

Meridional Effect

145.Click-right to quit the Detect Channel Matching Connection tool

Both connections between the meridional effect and the channel are recog-nized as matching connections.

148.Go to QAP Mesh Control

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Meridional Effect

Mesh Generation

151. Go to File -> Save Project As <tutorial1_match> <Enter> to save mesh and template

files

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TUTORIAL 2:

Non-Axisymmetric

Hub/Shroud

2-1

Introduction

2-1.1

Introduction

The resolution of computational fluid dynamics (CFD) problems involves three main steps:

•

spatial discretization of the flow equations

•

flow computation

•

visualization of the results

To answer these questions, NUMECA has developed a Flow INtegrated Environment for internal and Turbomachinery assimilations. Called FINE™/Turbo, the environment integrates the following tools:

•

IGG™ is an Interactive Geometry modeler and Grid generator software, based on structured multi-block techniques

•

AutoGrid™ is a three-dimensional Automated Grid generation software, dedicated to turboma-chinery applications. Similarly to IGG™, it is based on structured multi-block techniques

•

Euranus is a state-of-the-art multi-block flow solver, able to simulate Euler and Navier-Stokes equations in the laminar, transitional and turbulent regimes

•

CFView™ is a highly interactive flow visualization and post-treatment software

•

FINE™ Graphical User Interface is a user-friendly environment that includes the different soft-wares. It integrates the concept of projects and allows the user to achieve complete simulations, going from the grid generation to the flow visualization, without the need of file manipulation A turbomachine is a device in which the energy is transferred either to or from a continuously flow-ing fluid by the dynamic action of one or more movflow-ing blade rows. It plays a major role in particu-lar in aircraft, marine space (liquid rockets), land propulsion system but also in hydraulic, gas and steam turbines applications. It is also involved in industrial pipeline and processing equipment such as gas, petroleum and water pumping plants. Other applications can be related to heart-assist pumps, industrial compressors and refrigeration plants, among others.

The turbomachinery field includes turbines, pumps, fans, compressors. A turbomachine is com-posed of several basic elements including the blade (also called vane if it is non-rotating), hub, and shroud. Several technological effects involving clearances, seal leakages and cooling holes among

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Non-Axisymmetric Hub/Shroud

Introduction

others can complete the machine. Due to the complexity of the blade shapes, the presence of tech-nological elements and the rotation of machine, the nature of the flow is strongly three-dimensional, often depicting complex flow paths.

This tutorial is particularly adapted to the mesh generation of a turbomachine presenting a hub

and/or shroud non-axisymmetric. It makes exclusive use of AutoGrid™ v8 and describes the

main actions required to mesh the configuration of interest. In this tutorial you will learn how to:

•

Read an existing geometrical file into AutoGrid™ v8;

•

Control meridional flow paths when hub/shroud non-axisymmetric;

•

Control blade-to-blade mesh;

•

Control the mesh projection on the hub/shroud non-axisymmetric;

•

Control the quality of the mesh in the blade-to-blade and 3D mesh.

2-1.2

Prerequisites

This tutorial does not require any particular prerequisite but it is strongly recommended for begin-ners to perform the basic tutorials 1 to 7.

2-1.3

Problem Description

The problem to be considered is shown schematically here below. The project consists in the mesh generation of a Aachen turbine stator (treated as an isolated axial-flow wheel) when presenting a non-axisymmetric hub.

2-1.4

Preparation

•

Copy the files located in cdrom:\DOC\_Tutorials\AutoGrid\_advanced\Tutorial_2 to your working directory, where cdrom must be replaced by the name of your DVD-ROM.

•

Start AutoGrid™ v8.x

For LINUX and UNIX systems, you can access AutoGrid™ v8.x graphical user interface with the following command line

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Introduction

Non-Axisymmetric Hub/Shroud

For WINDOWS systems, you can access AutoGrid™ v8.x graphical user interface from the start menu going to /Programs/NUMECA software/fine8x/IGG or /Programs/NUMECA software/autogrid8x/IGG

•

Access the menu Modules, select AutoGrid and confirm "yes" to enter AutoGrid™ v8. You’re now ready to start the grid generation process and mesh the non-axisymmetric configuration! AutoGrid™ v8 graphical user interface includes several windows that allow to visualize the geom-etry and mesh of the turbomachine simultaneously in the meridional, blade-to-blade and 3D view. The access to main menu and controls is proposed through a menu bar and a quick access pad, and is completed with a tool/icon bar. The execution of the different actions undertaken is summarized in the message box at the bottom of the interface.

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Non-Axisymmetric Hub/Shroud

Mesh Generation

2-2

Mesh Generation

A step by step approach is proposed in the following lines. It aims at driving you through the vari-ous steps that need to be executed from the creation of the mesh project to the validation of the final mesh quality.

2-2.1

Create Mesh Project

1. Close the Open Turbo Project Wizard dialog box

2. Go to menu File -> New Project

3. Click yes to close the active project

4. Choose the icon Start a New Project From Scratch

The Open Turbo Project Wizard dialog box enables the user to retrieve a ".trb" file (with associated grid) including the data required to regenerate a mesh on an identical or similar geometry. In this tutorial, these data will be progressively introduced based on the geometry of the project case.

2-2.2

Load Geometry & Define Main Properties

5. Click-left row1 in Rows Definition row 1 in the Quick Access Pad (QAP) to activate

the current row

6. Click-left in the meridional view

7. Go to Geometry Definition Import and Link CAD Graphic window opens, allowing geometry import.

8. Click-left on File Open...

9. Select geometry.dat file from the file chooser

10.Define the hub curve

•

Click-left on the hub as it turns to yellow

•

Click-right and select Link to Hub

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Mesh Generation

Non-Axisymmetric Hub/Shroud

11.Define the shroud curve

•

Click-left on the shroud as it turns to yellow

•

Click-right and select Link to Shroud

Shroud curve is displayed in the meridional view.

In addition to the axisymmetric hub and shroud curves defining the meridi-onal domain, 3D surfaces defining the non-axisymmetric end walls must be defined. These can be directly specified in the ".geomTurbo" file (more details in User Manual) or imported through the Import CAD window.

12.Define the non-axisymmetric surface defining the hub

•

Click-left on the surface defining the hub when highlighted in blue, it turns to yellow

•

Click-right and select Link Non Axi to Hub

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Non-Axisymmetric Hub/Shroud

Mesh Generation

The 3D surfaces defining the non-axisymmetric end walls must present the same peridiocity as the row.

13.Define the blade

•

Click-left on first surface defining the blade when highlighted in blue (it turns to red or yel-low)

•

Click-middle to select the second surface defining the blade

•

<Shift> - click-left on second surface defining the blade when highlighted in blue (it turns to red or yellow)

The View/View Solid menu acts as a toggle and allows to visualize the sur-faces that are active.

•

Click-right and select Link to Blade

Blade is displayed in the meridional view.

Click Middle Click Left

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Mesh Generation

Non-Axisymmetric Hub/Shroud

14.Define leading edge and trailing edge

•

Click-left at blade leading edge line definition, inside the Import CAD window

•

As it turns yellow, click-right and select Link to Leading Edge

•

Click-left at blade trailing edge line definition, inside the Import CAD window

•

As it turns yellow, click-right and select Link to Trailing Edge

Leading and trailing edges are displayed in the meridional view.

When blade intersect hub and shroud, inlet and outlet are displayed in the meridional view.

15.Go to File -> Exit

16.Click-left on Rows Definition row 1 to activate row1

17.Click-right on row 1 to get the contextual menu and select Properties

18.Enter the Periodicity (number of blades). Left-click inside the string input area and type <36>, press <Enter> to confirm

19.Enter <0> in Rotation Speed (rpm)

This speed will be transferred to FINE™ graphical user interface and ease the input of boundary conditions later on.

The sign of the rotational speed is positive (+) when the blade row is rotating in the positive θ direction, and negative otherwise.

20.Select Stator as a row type and Axial as a row orientation

The row type and row orientation settings are only information that will not impact or control the mesh generation process.

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Non-Axisymmetric Hub/Shroud

Mesh Generation

The non axisymmetric end walls generation is controlled into the Row Proper-ties dialog box.

21.Keep Non-Axisymmetric Hub active

The "Non-Axisymmetric Hub & Shroud" is used to enable or disabled the mesh adaptation on the specified non axisymmetric surfaces.

22.Keep Projection Along Face Normal active by default

When the non axisymmetric surface is not intersecting the axisymmetric mesh: The "Projection Along Face Normal" is projecting the mesh on the surface using the hub or shroud normal face directions. Therefore, as on the con-nected face boundary the computed normal can be different for both faces, the matching connection may become non-matching.

The "Projection Along Grid Line" is projecting the mesh on the surface using the spanwise grid line direction to compute the normal. This approach allows to avoid non-matching connections.

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Mesh Generation

Non-Axisymmetric Hub/Shroud

The "Repair Non-projected Points" allows to correct non-well projected points (i.e. when the mesh points on boundaries are close to hub or shroud surface limits).

24.Set the Geometry Repetition to <2><Enter>

The non-axisymmetric 3D surfaces must cover all the hub or shroud blade to blade domain of the axisymmetric mesh. If the specified surfaces does not cover the entire domain as shown in the next figure, the Geometry Repetition option allows the user to repeat the entered surfaces by rotation on both sides.

The "Display Non-Axisymmetric Hub & Shroud" is used to display the non-axisymmetric surfaces in the 3D view

At the end of the 3D blade row generation, the mesh adaptation on the non-axisymmetric surfaces is performed automatically. The non-axisymmetric mesh is adapted by hub to shroud grid points redistribution along the curve obtained by intersecting the surfaces with the hub to shroud grid lines. It is thus recom-mended to generate a axisymmetric mesh covering completely the non-axisymmetric surfaces.

26.Click-left in the meridional view

27.Go to Geometry Definition Import and Link CAD

28.Click-left on the surface defining the hub when highlighted in blue, it turns to yellow

29.Select Geometry/Modify Surface/Add uv Curves

30.Click-left on the surface in order to define new curves plotting the non-axisymmetry appearing on the hub

31.Click-left on the new curve until it turns yellow

32.Click-right and select Import Meridional

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Non-Axisymmetric Hub/Shroud

Mesh Generation

The limit of the non-axisymmetric hub is appearing in the meridional view.

33.Move hub curve to create a channel including the non-axisymmetric effect

•

Click-left in the meridional view

•

Go to Geometry Definition Edit Hub to visualize the vertices defining the hub

•

Click-left on vertex (at inlet) and define its new position in the keyboard input area in ZRTH coordinates where Z is the Z_inlet and R is lower than the R_min of the non-axisymmet-ric effect: <-0.03 0.242 0><Enter>

•

Click-left on vertex (at outlet) and define its new position in the keyboard input area in ZRTH coordinates where Z is the Z_outlet and R is lower than the R_min of the non-axisym-metric effect: <0.054737609091 0.242 0><Enter>

•

Click-right to regenerate the channel

The hub appears as a dashed green line because it is no more mapping on a curve.

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Mesh Generation

Non-Axisymmetric Hub/Shroud

The blade is no more intersecting the new hub. The blade needs to be extended.

34.Click-left on Rows Definition row 1 Blades Main Blade

35.Click-right on Main Blade to get the contextual menu and select Expand Geometry

36.Select Hub treatment/expand

•

Set Cut offset to <0.001><Enter>

•

Set Extension offset to <0.001><Enter>

•

Apply to extend the blade

The tool Geometry/Distance allows to measure the distance between two points in the active view.

2-2.3

Set Default Topology

37.Click-left on Rows Definition -> row 1 to activate the row, if not done already

38.Select Grid Level/Medium through Mesh Control in Quick Access Pad

≈ 0.0003 [m]

Cut Offset = 0.001 [m]

Expand Offset = 0.001 [m]

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Non-Axisymmetric Hub/Shroud

Mesh Generation

39.Estimate the width of the first cell at the wall:

The width of the first cell close to the wall must be selected with care since the quality of the flow solution will often depend upon the capture of the flow phe-nomena inside the boundary layers which develop along the solid walls. Depending upon the turbulence model selected, NUMECA recommends to locate the nearest grid point along the wall, at a distance that corresponds to parietal coordinate y+ ranging from 1-5 (low Reynolds number models) or 30-50 (high Reynolds number models). Assuming thermal effects must be mod-elled accurately, y+ can reach values as low as 0.1.

The relation between the parietal coordinate y+ and width of the first cell close to the wall y is driven by the Blasius equation, expressed as follows for turbulent flows:

where:

- y_wall is the distance of the nearest grid point to the wall (in meter);

- V_ref is a reference velocity of the flow, for instance the inlet velocity (in m/s); - υ is the kinematic viscosity of the fluid (in m2/s), i.e. the dynamic viscosity divided by the density;

- L_ref is a reference length of the test case (in meter); - y+ is a non-dimensional value.

In the present case, one can estimate that V_ref=30 m/s, L_ref=0.3m and υ=1.038e-5 m2/s Assum-ing one wishes to get y+ =1 at the wall, it comes that y = 1 x 10-5 m. Input the value of the Cell

Width = <1e-5> <Enter> in Row Mesh Control.

40.Select (Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology

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Mesh Generation

Non-Axisymmetric Hub/Shroud

The flow paths are covering the non-axisymmetric hub.

The default skin-topology includes 5 blocks as follows: - the skin block is a O-mesh surrounding the blade

- the inlet block is a H-mesh located upstream the leading edge - the outlet block is a H-mesh located downstream the trailing edge - the up block is a H-mesh located above the blade section

- the down block is a H-mesh located under the blade section

2-2.4

Meridional Control

41. Go to QAP Mesh Control

43.Control flow paths if necessary through Mesh Control -> Row Mesh Control -> Flow

Paths Control skin block down block outlet block up block inlet block

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Non-Axisymmetric Hub/Shroud

Mesh Generation

The Expert section allows the user to control the visualization, the shape and the parameters related to flow path smoothing. The meaning of these parame-ters is detailed in the user manual.

The Manual Edition mode allows the user to control directly the block faces which are used to construct flow paths. Edges can be moved, segments can be created or modified and grid points distribution on segments can be control-led. More details can be found in the user manual.

44.Keep data identical

45.Click on Generate

2-2.5

Blade-to-Blade Control

47.Click on Generate B2B

48.Go to

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Mesh Generation

Non-Axisymmetric Hub/Shroud

By default, non-matching connections are applied at periodic boundaries. Matching connections at periodic boundaries can be obtained by activating the Matching Periodicity check button. Press Re(set) Default Topology to re-generate the mesh in the blade-to-blade plane.

In most cases, the presence of non-matching connections somehow improves the orthogonality in the overall mesh. This is especially true in highly stag-gered configurations.

49.Keep Matching Periodicity deactivated and all other data identical

In several turbomachinery types, the blades are highly staggered (Automatic

High Staggered Blade Detection within AutoGrid™). If the solid angle at the inlet (outlet) of the machine becomes greater than 450_{and if the location of}

the inlet (outlet) limits of the domain is close to the leading edge (trailing edge) of the blades, then the default topology is not suitable anymore since the cells located near the inlet (outlet) boundary become very skewed. To improve this unexpected behaviour, AutoGrid™ uses the High Staggered Blade

Opti-mization.

50.Deactivate Topology option

51.Go to Mesh Control Row Mesh Control B2B Mesh Topology Control -> Grid Points to control the number of grid points in the blade-to-blade view

52.Click-left on the number of nodes, make the proper modification in the entry box and press <Enter> to confirm the modification

The number of points specified is recommended to be 4xn + 1 (where n is an

integer) to allow multigrid process on minimum 3 grid levels within FINE™.

53.Visualize the result in blade-to-blade view after selecting Generate B2B to regenerate the flow paths and the mesh in blade-to-blade plane.

54.Deactivate Grid Points option

55.Close the dialog box.

56.Go to Mesh Control-> Active B2B Layer to specify the flow path (layer) on which the blade-to-blade mesh will be plotted in the blade-to-blade view

Tutorial Guide AutoGrid 82 1 Advanced-Acrov5

Advanced Tutorials

AutoGrid™ v8

-Advanced Tutorials

AutoGrid™ v8.c

Documentation v8.c

NUMECA International

5, Avenue Franklin Roosevelt

1050 Brussels

Belgium

Tel: +32 2 647.83.11

Fax: +32 2 647.93.98

Web: http://www.numeca.com

Contents

TABLE OF CONTENT

INTRODUCTION

TUTORIAL 1: Meridional Effect

TUTORIAL 2: Non-Axisymmetric Hub/Shroud

Contents

TUTORIAL 3: Bypass Configuration

TUTORIAL 4: Tandem Row

Contents

TUTORIAL 5: Cascade Configuration

TUTORIAL 6: Fin on Fan

Contents

TUTORIAL 7: 3D Technological Effect - Casing Treatment

What’s in This Guide ?

Where to Find the Files Used in the Tutorials ?

How to Use this Guide ?

For the Beginner

For the Experienced User

Conventions Used in this Guide

TUTORIAL 1:

Meridional Effect

1-1

Introduction

1-1.1

Introduction

•

•

•

•

•

•

•

•

Meridional Effect

Introduction

•

•

•

•

1-1.2

Prerequisites

1-1.3

Problem Description

1-1.4

Preparation

•

•

Introduction

Meridional Effect

•

Meridional Effect

Mesh Generation

1-2

Mesh Generation

1-2.1

Create Mesh Project

1-2.2

Load Geometry & Define Main Properties

•

•

Mesh Generation

Meridional Effect

•

•

•

•

•