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Close dialog box12.Define the hub curve
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<Shift> - click-left on all the curves defining the hub as they turn to yellow•
Click-right and select Link to HubHub curve is displayed in the meridional view.
13.Define the shroud curve
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<Shift> - click-left on all the curves defining the shroud as they turn to yellow•
Click-right and select Link to ShroudShroud curve is displayed in the meridional view.
14.Define the blade
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Click-left row1 in Rows Definition row 1 in the Quick Access Pad (QAP) to activateCascade Configuration
Mesh Generation
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Click-left on the surface defining the blade when highlighted in blue (it turns to red or yel- low)If the blade is defined by multiple surfaces, click-middle and <Shift>-click-left allow to select all the surfaces defining the blade.
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 and select Link to BladeBlade is displayed in the meridional view.
15.Define leading edge and trailing edge
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Click-left row1 in Rows Definition row 1 in the Quick Access Pad (QAP) to activatethe current row, if not done already
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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 EdgeLeading and trailing edges are displayed in the meridional view.
Mesh Generation
Cascade Configuration
When blade intersects hub and shroud, inlet and outlet are displayed in the meridional view.
16.Go to File -> Exit
The geometry of the cascade configuration can also be defined from a native ".geomTurbo" file.
The ".geomTurbo" file format is structured in three main blocks: the header, the channel and the row(s) definitions.
The header when defining a cascade configuration should contain the key- words "cascade yes".
The channel format contains the definition of the turbomachinery meridional contour (hub and shroud). It is composed by curves defined by a set of points. The ".geomTurbo" file must contain two channel curves named respectively "hub" and "shroud".
The row definition contains the geometry of a complete row. The blade is defined by the pressure and the suction side surfaces identified by the key- words "pressure" and "suction". Both surfaces are specified by a set of cross sections of the blade at several spanwise location from hub to shroud. Each section is defined by a set of points from leading to trailing edge.
Cascade Configuration
Mesh Generation
17.Click-left on Rows Definition -> row 1 in the Quick Access Pad (QAP) to active it
18.Click-right on row 1 and select Properties in the pop-up menu
19.Enter the Periodicity (number of blades) to <79.9><Enter>
The periodicity for cascade configuration corresponds to the pitch distance between two successive blades.
20.Enter <0> in Rotation Speed (rpm)
The speed will be transferred to FINE™ graphical user interface and ease the input of boundary conditions later on.
21.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.
22.Close the dialog box
23.Set the scaling factor
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Go to Geometry Definition UnitsMesh Generation
Cascade Configuration
The "units" of the imported geometry must be changed to impose a scaling factor and a corresponding tolerance that will ensure correct treatment dur- ing the grid generation when computing for example the intersection. If not necessary, we recommend to keep the default settings (Scale Factor set to 1)
24.Click-left on Select All Rows
25.Select toggle 3D Solid View in the View menu to access the shaded blades in 3D view
26.Select toggle 3D Solid View in the View menu to remove the shaded blades in 3D view
5-2.3
Set Default Topology
27.Click-left on Select All Rows
28.Select Grid Level/Medium through Mesh Control in Quick Access Pad
29.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:
- ywall is the distance of the nearest grid point to the wall (in meter);
- Vref 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;
- Lref is a reference length of the test case (in meter); - y+ is a non-dimensional value.
Cascade Configuration
Mesh Generation
Input the value of the Cell Width = <5e-3> [Millimeters] <Enter> in Row Mesh Control.
30.Select (Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology
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