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Fully Developed Free Convection Flow in a Vertical Slot with Open to Capped Ends: D’Alembert’s Approach

Fully Developed Free Convection Flow in a Vertical Slot with Open to Capped Ends: D’Alembert’s Approach

Abstract: The fully developed free convection flow in a vertical slot with open to capped ends discussed by Weidman [5] and Magyari [6] is scrutinized in this present work. Exact solution of momentum and energy equations under relevant boundary conditions as discussed in [5, 6] is obtained using the D’Alembert’s method. Numerical comparison of this present work is made with previous result of [6] and the results were justified using the well-known implicit finite difference method (IFDM); this gives an excellent comparison. During the course of numerical investigation, it is found that D’Alembert’s approach is a simpler, reliable and accurate tool for solving coupled equations.

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Verification of fully developed flow entering diffuser and particle image velocimetry procedures

Verification of fully developed flow entering diffuser and particle image velocimetry procedures

Abstract. 3-D stereoscopic PIV is capable of measuring 3-dimensional velocity components. It involves a very sophisticated routine during setup, calibration, measurement and data processing phases. This paper aims to verify the 3-D stereoscopic PIV measurement procedures and to prove that the flow entering the diffuser is a fully developed flow. A diffuser inlet of rectangular cross- section, 130 mm x 50 mm is presently considered. For verification, the velocities from PIV are compared with the velocities from pitot static probe and theory. The mean velocity obtained using pitot static probe is 2.44 m/s, whereas using PIV is 2.46 m/s. It thus gives the discrepancy of 0.8%. There is also a good agreement between the mean velocity measured by PIV and theoretical value with the discrepancy of 1.2%. This minor discrepancy is mainly due to uncertainties in the experiments such as imperfect matching of coordinates between the probe and laser sheet, unsteadiness of flow, variation in density and less precision in calibration. Basically, the operating procedures of 3-D stereoscopic PIV have successfully been verified. Nevertheless, the flow entering diffuser is not perfectly developed due to the imperfect joining duct and the abrupt change of inlet cross-section introduced. Therefore, improvement to the existing rig is proposed by means of installing settling chamber with multiple screens arrangement and contraction cone.

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Distinct Organizational States of Fully Developed Turbulent Pipe Flow

Distinct Organizational States of Fully Developed Turbulent Pipe Flow

The question of how experimental data can best be analyzed in order to show the presence (or otherwise) of exact coherent states is an open one. In this Letter we present, through the use of a novel analysis technique applied to a large-scale experiment, evidence suggestive of the presence of nonlinear traveling-wave invariant solutions in fully developed turbulent pipe flow at a Reynolds number significantly higher than that at which they have been previously observed. In so doing we not only provide the first evidence for the potential relevance of dynamical systems based solutions applied to higher Re flows, but Published by the American Physical Society under the terms of

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Imbalance of energy and momentum source terms of the sea wave transfer equation for fully developed seas

Imbalance of energy and momentum source terms of the sea wave transfer equation for fully developed seas

In order to compute the integral quantities of Eqs. (5a) and (5b), one needs to use a model for the sea wave spec- trum based on observations. As concerns the omnidirec- tional spectrum, I used the empirical sea wave spectral model by Elfouhaily et al. (1997) for different conditions of wind speed, assuming fully developed situations. An advantage of this model is that it describes the wave spectrum over the whole range of wavenumbers – from the spectral peak to capillary waves – on a purely empirical basis. Also, while this model was tuned on in situ observations of wave spectra performed both in ocean and in laboratory settings, it is also consistent with the optical mean square slope measurements by Cox and Munk (1954).

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3D Fully Developed Laminar Mixed Convection in Horizontal Concentric Annuli with the Presence of Porous Blocks

3D Fully Developed Laminar Mixed Convection in Horizontal Concentric Annuli with the Presence of Porous Blocks

shown in Fig. 1. Four porous blocks are fixed on outside of the inner cylinder. The porous blocks are considered homogeneous, isotropic and saturated by an incompressible fluid. The outer cylinder is insulated while the inner cylinder has circumferentially uniform surface temperature and axially uniform heat transfer rate. In the fully developed region of the flow, the velocity components become independent of the axial distance z. The density of fluid is considered constant except in the buoyancy term (Boussinesq approximation). A local thermal equilibrium takes place between the fluid and the porous medium. Because of the symmetry about the vertical center line shown in Fig. 1, the analysis is confined to a right half of the annulus.

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Entropy generation calculation for laminar fully developed forced flow and heat transfer of nanofluids inside annuli

Entropy generation calculation for laminar fully developed forced flow and heat transfer of nanofluids inside annuli

In the nanofluids flows, the improvement of the heat transfer properties causes the reduction in entropy generation. On the other hand, the increment in pressure drop gives more irreversibility and exergy loss in systems. Bejan [16] stated that when the entropy generation is minimized, the optimum design condition of a thermal system will be obtained. In the other words, the best design of heat exchangers is the one which includes considerations for how to increase heat transfer performance and reduce the pressure drop. Ko and Ting [17] have applied this concept to find the most appropriate flow conditions of a fully developed, laminar forced convection flow through a helical coil tube for which entropy generation is minimized. Ko [18] obtained the optimal mass flow rate for fully developed laminar forced convection in a helical coiled tube based on minimal entropy generation principle. Nag and Naresh [19] have studied second law optimization of convective heat transfer through a duct with constant heat flux.

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Comparisons of Lung Structure of Fully Developed Domestic Fowl With Duck, Through Orientation to Broiler Ascites

Comparisons of Lung Structure of Fully Developed Domestic Fowl With Duck, Through Orientation to Broiler Ascites

This comparative study of the structure in lungs of the fully developed female domestic fowl and the duck. In the avian lung gas exchanging region, while proportionally smaller than mammalian lung, competently manages respiration to meet the high active necessities of flapping flight. The domestic fowl has partially remunerated for this by raising the surface area for gas exchange per unit volume of exchange tissue. . In domestic bird the size of the lung per unit body weight is between 20 and 33% lesser than that of the wild bird.

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Numerical Investigation of Nano Particles Dispersion and Deposition in Fully Developed Laminar Pipe Flows

Numerical Investigation of Nano Particles Dispersion and Deposition in Fully Developed Laminar Pipe Flows

Validity of the present st udy is examined by comparing the simulation results for particle deposition efficiency in tubular pipes with the exi st ing analytical correlations in the literature. These correlations were developed based on the dimensionless diffusion parameter Δ for fully developed laminar pipe flows with the parabolic velocity profile at the inlet. One of the frequently used correlations was developed by Ingham [5] which is given as:

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Speckle Suppression by Integrated Sum of Fully Developed Negatively Correlated Patterns in Coherent Imaging

Speckle Suppression by Integrated Sum of Fully Developed Negatively Correlated Patterns in Coherent Imaging

Note that the speckle contrast in terms of an intensity ratio can be used to evaluate the effect of speckle suppression for the summed pattern of multiple partially developed speckle patterns that are uncorrelated [24]. Using Equation (6), however, will result in a direct comparison of the summed pattern and the individual patterns with speckles not only fully developed but also partially developed.

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An active power control approach for wake-induced load alleviation in a fully developed wind farm boundary layer

An active power control approach for wake-induced load alleviation in a fully developed wind farm boundary layer

Abstract. This paper studies a closed-loop wind farm control framework for active power control (APC) with a simultaneous reduction of wake-induced structural loads within a fully developed wind farm flow interacting with the atmospheric boundary layer. The main focus is on a classical feedback control, which features a simple control architecture and a practical measurement system that are realizable for real-time control of large wind farms. We demonstrate that the wake-induced structural loading of the downstream turbines can be alleviated, while the wind farm power production follows a reference signal. A closed-loop APC is designed first to im- prove the power-tracking performance against wake-induced power losses of the downwind turbines. Then, the nonunique solution of APC for the wind farm is exploited for aggregated structural load alleviation. The axial in- duction factors of the individual wind turbines are considered control inputs to limit the power production of the wind farm or to switch to greedy control when the demand exceeds the power available in the wind. Furthermore, the APC solution domain is enlarged by an adjustment of the power set-points according to the locally available power at the waked wind turbines. Therefore, the controllability of the wind turbines is improved for rejecting the intensified load fluctuations inside the wake. A large-eddy simulation model is employed for resolving the turbulent flow, the wake structures, and its interaction with the atmospheric boundary layer. The applicability and key features of the controller are discussed with a wind farm example consisting of 3 × 4 turbines with different wake interactions for each row. The performance of the proposed APC is evaluated using the accuracy of the wind farm power tracking and the wake-induced damage equivalent fatigue loads of the towers of the individual wind turbines.

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Turbulent temperature profile in the quasi-fully developed region of a micro-tube

Turbulent temperature profile in the quasi-fully developed region of a micro-tube

Design and fabrication of Micro Electro Mechanical Systems (MEMS) have increased the need for understanding of fluid flow and heat transfer in micron-sized channels. The transverse velocity gradient for flow in micron-sized channel is quite high and results in large pressure drop. For the case of gas flow in micro-tube, the flow accelerates even far away from the entrance and therefore, it does not become fully developed. However, the changes in the flow direction are small compared with the radial direction and the velocity in the r-direction can be assumed to be zero. The region where the axial velocity and temperature gradients (e.g.  u  x ,  T  x ) and the radial velocity are small and also the density can be considered constant is called quasi-fully developed region (Asako et al., 2003).

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Comparative Analysis Fully Developed Turbulent Flow in Various Arbitrary Cross Section Ducts using Finite Volume Approach

Comparative Analysis Fully Developed Turbulent Flow in Various Arbitrary Cross Section Ducts using Finite Volume Approach

Figure 9 shows the comparison of skin friction coefficient between circular, triangular and rectangular duct. It has seen that the skin friction coefficient gradually increases as the Reynolds number increases. The rate of augmentation of skin friction coefficient is noteworthy at higher Reynolds number. On comparative analysis triangular duct has more skin friction coefficient as compared to circular and rectangular duct. It has been found that the rectangular duct has 8.45% lower skin friction coefficient as compared to triangular duct at fully developed turbulent flow.

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New Achievements in Fe3O4 Nanofluid Fully Developed Forced Convection Heat Transfer under the Effect of a Magnetic Field: An Experimental Study

New Achievements in Fe3O4 Nanofluid Fully Developed Forced Convection Heat Transfer under the Effect of a Magnetic Field: An Experimental Study

Nusselt number in a two-dimensional cavity. They introduced a general relationship for the Nusselt number. The flow between two parallel surfaces exposed to a source line of a dipolar magnetic field demonstrated increased heat transfer [21]. Belayaev and Smorodin described ferrofluid heat transfer in an alternating magnetic field, [22] in light of the external magnetic field frequency and power, layer thickness, and temperature. Li and Juan [23] conducted studies on the effect of uniform and non-uniform magnetic fields on ferrofluid convection at low Reynolds numbers. They concluded that this magnetic field can substantially influence the heat transfer process. Ferrofluid properties, such as viscosity and conductivity, may be exposed to an external magnetic field, thereby precisely controlling the rheological properties. Furthermore, as mentioned earlier, ferrofluids can improve heat transfer. Therefore, this capability has been of great interest to many. However, the forced convection of ferrofluids has not been rigorously studied. Lajvardi et al. [24] investigated heat transfer under the effect of a constant magnetic field. The results revealed a considerable increase in heat transfer; however, there is a small number of such studies. There is empirical research on increasing the forced convection of laminar and turbulent flows in relation to various things, such as the effect of particle type and thickness. The results of such research have led to a substantial increase in the heat transfer coefficient. However, ferrofluid heat transfer has not been sufficiently studied. The ferrofluid heat transfer process under the effect of an alternating magnetic field is very complex. Empirical research would be of great help in studying this phenomenon. Ghofrani et al. [25] investigated the laminar forced convection heat transfer of ferrofluids under an alternating magnetic field and a “developing flow” regime. However, the effect of an alternating magnetic field in a fully developed flow regime is vague. In this research, after procuring and validating the experimentation device, the effect of a constant magnetic field and an alternating magnetic field frequency on Fe 3 O 4 fully developed forced

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Numerical Analysis of Fully Developed Flow and Heat Transfer in Channels with Periodically Grooved Parts (TECHNICAL NOTE)

Numerical Analysis of Fully Developed Flow and Heat Transfer in Channels with Periodically Grooved Parts (TECHNICAL NOTE)

Metwally and Manglik [7] and Zhang et al. [8] numerically investigated the effects of waviness configuration; its spacing and Reynolds number on flow and heat transfer characteristics in channels with sinusoidal channel for steady and laminar flow regime. Ramgadia and Saha [9] solved time-dependent Navier– Stokes and energy equation through a wavy channel. Effect of geometry, i.e. minimum and maximum height between two wavy walls, on fluid flow and heat transfer characteristics elaborated at a Reynolds number of 600. Pashaie et al. [10]developed an adaptive neuro-fuzzy inference system to determine Nusselt number along a sinusoidal wavy wall in a lid-driven cavity.

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Fully Developed Circular Pipe Flow of a Non Newtonian Pseudoplastic Fluid

Fully Developed Circular Pipe Flow of a Non Newtonian Pseudoplastic Fluid

The velocity distribution in fully-developed flow of a non-Newtonian pseudoplastic fluid through a circu- lar pipe has been computed using a modified power-law. The parameters in the modified power-law have been de- termined to fit available experimental data for the vari- ation of the non-Newtonian viscosity of a 0.4 % poly- acrylamide solution with shear-rate. A non-dimensional shear-rate parameter governing the flow has been deter- mined; this non-dimensional parameter, A, depends on the applied pressure gradient. The results indicate that at low values of the shear-rate parameter, the velocity predicted by the modified power-law is higher than the velocity predicted by the power-law. At high values of the shear-rate parameter, the velocity predicted by the modified power-law is lower than the velocity predicted by the power-law. The velocities predicted by the mod- ified power-law and the power-law are almost identical at intermediate values of the shear-rate parameter. At very low values of the shear-rate parameter, the velocity profile predicted by the modified power-law is identical to that for fully-developed flow of a Newtonian fluid with

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Analysis of phase coherence in fully developed atmospheric turbulence: Amazon forest canopy

Analysis of phase coherence in fully developed atmospheric turbulence: Amazon forest canopy

has been developed for nonlinear space data analysis (Hada et al., 2003; Nariyuki and Hada, 2006; Koga et al., 2008). The link between phase coherence, non-Gaussianity and in- termittent turbulence was established by Koga et al. (2007), based on GEOTAIL magnetic field data upstream and down- stream of the Earth’s bow shock. The aim of this paper is to apply the kurtosis (fourth-order structure function) and phase coherence techniques to determine the intermittent na- ture of day-time atmospheric turbulence above and within the Amazon forest canopy. In particular, we show that both techniques are capable of characterizing the dissimilarity of scalar and velocity in above-canopy and in-canopy atmo- spheric turbulence.

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Large-Eddy Simulations of Fully Developed Turbulent Channel and Pipe Flows with Smooth and Rough Walls

Large-Eddy Simulations of Fully Developed Turbulent Channel and Pipe Flows with Smooth and Rough Walls

The second stage of development has simulated pipe flow in a Cartesian coordinate system, which eliminates pole singularities. The conversion from planar to curvilinear wall boundaries has been presented and wall treatment has been covered. The performance of the spectral element method in under-resolved conditions has initially caused mean velocity profiles to be under-predicted by several percent when compared to the theoretically based log-law; turbu- lence statistics have been shown to be systematically downward biased. By applying a special treatment to the spectral element edge-nodes at the wall, this issue has been addressed and only partly remedied. Nonetheless, in spite of these errors, the friction factors obtained from the LES have shown agreement with those obtained in the experimental study of McKeon et al. [74] and have been used to calculate the K´arm´an constant and additive constant as κ = 0.43 and B = 5.5. Other possible improvements have been attempted, such as the various ways to calculate the LES cutoff wavelength, Laplacian smoothing of the grid spacing, and near-wall grid refinement, although no entirely satisfactory and systematic solution has been found through these approaches. An alternative appears to be grid refinement up to the level at which the flow is fully resolved and hence the SGS model can be turned off near the wall. This would clearly defeat the point of LES and hence is not pursued.

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Buoyancy Effect on the Fully Developed Air Flow in Concentric Inclined Annulus

Buoyancy Effect on the Fully Developed Air Flow in Concentric Inclined Annulus

No available investigations exist about the mixed convection of air (Pr=0.7) at thermally and hydrodynamically fully developed region of a vertical annulus with a heated inner cylinder and adiabatic outer cylinder because of no appreciable effect for any parameter on the behavior of heat and fluid flow process. As shown in Fig.(8), the axial parabolic profile is the same for all values of Rayleigh numbers , because of no cellular motion at vertical position  =0 , and angular locations , because of symmetry about vertical axis.

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Germination of Corylopsis seeds evaluated by X-ray imaging and cold stratification

Germination of Corylopsis seeds evaluated by X-ray imaging and cold stratification

A few mostly full Corylopsis seeds with obvious cavities germinated without showing any abnormal growth of seedlings (data not presented). The in- crease in the cavity area observed in partially emp- ty seeds may suggest that embryos and endosperm are not fully developed or are degenerated, as re- ported in European larch (Kosińki 1987). Immers- ing seeds in water coupled with X-ray imaging is a feasible and potentially cost-effective means to select small, viable seeds on a large scale, as com- pared to magnetic resonance imaging as investigat- ed with Styrax japonicus L. (Roh et al. 2004).

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Thermal hydraulic performance of convective boiling jet array impingement

Thermal hydraulic performance of convective boiling jet array impingement

moderate drop in the effectiveness of the single phase cooling, likely due to the increased confinement effects which tends to cause higher vertical channel velocities i.e. parallel to the impinging jets, which are known to wash out neighbouring jets when arranged in arrays and have a deleterious influence on the stagnation heat transfer. The figures also indicate that the higher cross flow channel velocities may also influence ONB, since it is noticed in Figure 10 that the higher spacing case transitions into the nucleate boiling regime at a noticeably lower heat flux and does not experience the superheat overshoot of the narrower channel. Interestingly, once ONB occurs for the smaller 1 mm channel, its boiling curve merges with that of the 2mm channel providing evidence that fully developed boiling heat transfer is not sensitive

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