Steady RANS of Flow and Heat Transfer in a Smooth and Pin-Finned U-Duct With a Trapezoidal Cross Section

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Kenny S.-Y. Hu ◽  
Xingkai Chi ◽  
Tom I.-P. Shih ◽  
Minking Chyu ◽  
Michael Crawford
Keyword(s):  
Heat Transfer ◽  
Relative Error ◽  
Turbulence Models ◽  
Separated Flow ◽  
Reynolds Stress Model ◽  
Navier Stokes ◽  
Maximum Relative Error ◽  
Flow And Heat Transfer ◽  
Pin Fins ◽  
Turn Region

Steady Reynolds-averaged Navier--Stokes (RANS) simulations were performed to examine the ability of four turbulence models—realizable k–ε (k–ε), shear-stress transport (SST), Reynolds stress model with linear pressure strain (RSM-LPS), and stress-omega RSM (RSM-τω)—to predict the turbulent flow and heat transfer in a trapezoidal U-duct with and without a staggered array of pin fins. Results generated for the heat-transfer coefficient (HTC) were compared with experimental measurements. For the smooth U-duct, the maximum relative error in the averaged HTC in the up-leg is 2.5% for k–ε, SST, and RSM-τω and 9% for RSM-LPS. In the turn region, the maximum is 50% for k–ε and RSM-LPS, 14.5% for RSM-τω, and 29% for SST. In the down-leg, SST gave the best predictions and RSM-τω being a close second with maximum relative error less than 10%. The ability to predict the separated flow downstream of the turn dominated the performance of the models. For the U-duct with pin fins, SST and RSM-τω predicted the best, and k–ε predicted the least accurate HTCs. For k–ε, the maximum relative error is about 25%, whereas it is 15% for the SST and RSM-τω, and they occur in the turn. In the turn region, the staggered array of pin fins was found to behave like guide vanes in turning the flow. The pin fins also reduced the size of the separated region just after the turn.

Steady RANS of Flow and Heat Transfer in a Smooth and Pin-Finned U-Duct With a Trapezoidal Cross Section

2018 ◽  
Author(s):  
Kenny S.-Y. Hu ◽  
Xingkai Chi ◽  
Tom I-P. Shih ◽  
Minking Chyu ◽  
Michael Crawford
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Relative Error ◽  
Turbulence Models ◽  
Separated Flow ◽  
Maximum Relative Error ◽  
Trapezoidal Cross Section ◽  
Flow And Heat Transfer ◽  
Pin Fins ◽  
Turn Region

Steady RANS were performed to examine the ability of four turbulence models — realizable k-ε (k-ε), shear-stress transport (SST), Reynolds stress model with linear pressure strain (RSM-LPS), and stress-omega RSAM (RSM-τω) — to predict the turbulent flow and heat transfer in a U-duct with a trapezoidal cross section and with and without a staggered array of pin fins. Results generated for the heat-transfer coefficient (HTC) were compared with experimentally measured values. For the smooth U-duct, the maximum relative error in the averaged HTC in the up-leg is 2.5% for k-ε, SST, and RSM-τω and 9% for RSM-LPS. In the turn region, that maximum is 14.5% for RSM-τω, 29% for SST, and 50% for k-ε and RSM-LPS. In the down-leg, SST gave the best predictions and RSM-τω being a close second with maximum relative error less than 10%. The ability to predict the secondary flow in the turn region and the separated flow downstream of the turn dominated in how well the models predict the HTC. For the U-duct with pin fins, k-ε predicted the lowest and the least accurate HTCs, and SST and RSM-τω predicted the best. For k-ε, the maximum relative error in the averaged HTC is about 25%, whereas it is 15% for the SST and RSM-τω, and they occur in the turn. In the turn region, the staggered array of pin fins was found to behave like guide vanes in turning the flow. The pin fins also reduced the size of the separated region just after the turn.

Flow and Heat Transfer Predictions for a Flat-Tip Turbine Blade

2002 ◽  
Author(s):  
Huitao Yang ◽  
Sumanta Acharya ◽  
Srinath V. Ekkad ◽  
Chander Prakash ◽  
Ron Bunker
Keyword(s):  
Heat Transfer ◽  
Reynolds Stress ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Computational Effort ◽  
Stress Model ◽  
Tip Leakage Flow ◽  
Flow And Heat Transfer ◽  
Pitch Direction ◽  
Blade Tip

Numerical calculations are performed to simulate the tip leakage flow and heat transfer on the GE-E3 High-Pressure-Turbine (HPT) rotor blade. The calculations are performed for a single blade with periodic conditions imposed along the two boundaries in the circumferential-pitch direction. Cases considered are a flat blade tip at three different tip gap clearances of 1%, 1.5% and 2.5% of the blade span. The numerical results are obtained for two different pressure ratios (ratio of inlet total pressure to exit static pressure) of 1.2 and 1.32 and an inlet turbulence level of 6.1%. To explore the effect of turbulence models on the heat transfer results, three different models of increasing complexity and computational effort (standard high Re k-ε model, RNG k-ε and Reynolds Stress Model) are investigated. The predicted tip heat transfer results are compared with the experimental data of Azad [1], and show satisfactory agreement with the data. Hear transfer predictions for all three turbulence models are comparable, and no significant improvements are obtained with the Reynolds-stress model.

CFD Prediction for Multi-Jet Impingement Heat Transfer

2009 ◽  
Author(s):  
Y. Q. Zu ◽  
Y. Y. Yan ◽  
J. D. Maltson
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Computational Cost ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Reynolds Stress Model ◽  
Large Eddy Simulation Model ◽  
Flow And Heat Transfer ◽  
Shear Stress Transport ◽  
Impingement Heat Transfer

In this paper, the flow and heat transfer characteristics of two lines of staggered or inline round jets impinging on a flat plate are numerically analyzed using the CFD commercial code FLUENT. Firstly, the relative performance of seven versions of turbulence models, including the standard k-ε model, the renormalization group k-ε model, the realizable k-ε model, the standard k-ω model, the Shear-Stress Transport k-ω model, the Reynolds stress model and the Large Eddy Simulation model, for numerically predicting single jet impingement heat transfer is investigated by comparing the numerical results with available benchmark experimental data. As a result, the Shear-Stress Transport k-ω model is recommended as the best compromise between the computational cost and accuracy. Using the Shear-Stress Transport k-ω model, the impingement flow and heat transfer under multi-jets with different jet distributions and attack angles are simulated and studied. The effect of hole distribution and angle of attack, etc. on the heat transfer coefficient of the target plate are examined.

scholarly journals Comparison of ω-Based Turbulence Models for Simulating Separated Flows in Transonic Compressor Cascades

1998 ◽  
Author(s):  
Tom C. Currie
Keyword(s):  
Turbulence Models ◽  
Separated Flow ◽  
Adverse Pressure Gradient ◽  
Reynolds Stress Model ◽  
Separated Flows ◽  
Navier Stokes ◽  
Test Case ◽  
Turbulent Dissipation ◽  
Transonic Compressor ◽  
Scale Variable

Separated flows in the DLR transonic compressor cascades TSG-91-8K and TSG-89-5 are simulated with a quasi-3D Navier-Stokes code using the zonal k-ω/k-ϵ “Shear Stress Transport” two-equation turbulence model of Menter and the multiscale Reynolds stress model of Wilcox. Both of these models use the specific turbulent dissipation rate ω as the length scale variable. The models are also used to simulate the low speed, separated flow, adverse pressure gradient test case of Driver. While both models predict results which are in good agreement with experiment for the latter test case, they yield relatively poor results, particularly for losses, for the cascade test cases, especially TSG-89-5 where separation occurs from both the suction and pressure surfaces. It is known from the cascade test results that the separations are laminar, so some improvement in agreement is achieved by suppressing transition to the separation points in the simulations. The poor accuracy of the models is believed to be related to severe non-equilibrium of turbulence production and dissipation predicted after the shock-induced separations.

Two-Equation Versus Reynolds-Stress Modeling in Predicting Flow and Heat Transfer in a Smooth U-Duct With and Without Rotation

2002 ◽  
Author(s):  
X. Gu ◽  
H.-W. Wu ◽  
H. J. Schock ◽  
T. I.-P. Shih
Keyword(s):  
Heat Transfer ◽  
Reynolds Stress ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Surface Heat ◽  
Small Radius ◽  
Stress Model ◽  
Surface Heat Transfer ◽  
Flow And Heat Transfer ◽  
Significant Difference

Computations were performed by using Version 5.5 of the Fluent-UNS code to compare two turbulence models in predicting the three-dimensional flow and heat transfer in a smooth duct of square cross section with a small radius of curvature 180-degree bend under rotating and non-rotating conditions (Re = 25,000; Ro = 0.0 and 0.24). The two turbulence models investigated are the standard k-ε model and a Reynolds stress model. For both models, the two-layer low-Reynolds model of Chen and Patel was used in the near-wall region. Results obtained show that though the k-ε model predicts turbulence quantities incorrectly, the predicted velocity and temperature fields and the surface heat transfer are similar to those from the Reynolds stress model when there is no rotation. When there is rotation, there is significant difference in the predicted surface heat transfer on the leading surface. But, the predicted flow field is still qualitatively similar.

Comparison Between EVM and RSM Turbulence Models in Predicting Flow and Heat Transfer in Rib-Roughened Channels

2004 ◽  
Author(s):  
A. K. Sleiti ◽  
J. S. Kapat
Keyword(s):  
Heat Transfer ◽  
Reynolds Stress ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Wall Region ◽  
Internal Cooling ◽  
Wall Functions ◽  
Flow And Heat Transfer ◽  
Near Wall ◽  
Rib Roughened

A 3-D analysis of two-equation eddy-viscosity (EVMs) and Reynolds stress (RSM) turbulence models and their application to solving flow and heat transfer in rotating rib-roughened internal cooling channels is the main focus of this study. The flow in theses channels is affected by ribs, rotation, buoyancy, bends and boundary conditions. The EVMs considered are: The standard k–ε Model: of Launder and Spalding Launder and Spalding [1], the Renormalization Group k-ε model: Yakhot and Orszag [2], the Realizable k-ε model Shur et al. [3], the standard k-ω Model, Wilcox Wilcox [4], and the Shear-Stress Transport (SST) k-ω Model, Menter [5]. The viscosity affected near wall region is resolved by enhanced near wall treatment using combined two-layer model with enhanced wall functions. The results for both stationary and rotating channels showed the advantages of Reynolds Stress Model (RSM), Gibson and Launder [6], Launder [7], Launder [8] in predicting the flow field and heat transfer compared to the isotropic EVMs that need corrections to account for streamline curvature, buoyancy and rotation.

Turbulent Forced Convection in a Plane Asymmetric Diffuser: Effect of Diffuser Angle

2007 ◽  
Author(s):  
H. Lan ◽  
B. F. Armaly ◽  
J. A. Drallmeier
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Forced Convection ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Separated Flow ◽  
Velocity Data ◽  
Measured Velocity ◽  
Flow And Heat Transfer ◽  
Diffuser Angle

Simulation of two-dimensional turbulent forced convection in a plane asymmetric diffuser is performed and the effect of diffuser angle on the flow and heat transfer is reported. This geometry is common in many heat exchanging devices and the convective heat transfer in it has not been examined. The flow field in this geometry, however, has received significant attention already and the results show that the υ2–f turbulence model provides a better comparison with measured velocity distributions than the k–ε turbulence models. This improvement in predictions is due to selecting different turbulent velocity scale and time scale for the eddy viscosity than what is used in conventional two-equation turbulence models. The results show that the diffuser angle influences significantly the flow field (separation and reattachment) and consequently, it must influence significantly the heat transfer. The υ2–f type turbulence models have been shown to provide good heat transfer results for separated flow, and for that reason a k-ε-ζ (or υ2–f type) turbulence model is used in this study. FLUENT 6.2.16 is used as the platform for these simulations and User Defined Functions (UDF) are developed to incorporate this turbulence model (which is not included in the commercial version of the FLUENT code at this time) into this CFD code. The UDF for the k-ε-ζ turbulence model is validated by comparisons with available measured velocity data in an asymmetric diffuser and with available measured heat transfer and velocity data in a backward facing step flow, and with heat transfer data for a normally-impinging jet flow with very good agreement between simulated and measured results.

scholarly journals Impingement Heat Transfer: Correlations and Numerical Modeling

2005 ◽  
Vol 127 (5) ◽  
pp. 544-552 ◽  
Author(s):  
Neil Zuckerman ◽  
Noam Lior
Keyword(s):  
Heat Transfer ◽  
Turbulence Models ◽  
Impinging Jet ◽  
Reynolds Stress Model ◽  
Model Errors ◽  
Simulation Techniques ◽  
Flow And Heat Transfer ◽  
Impingement Heat Transfer ◽  
Model Equations ◽  
Stress Models

Uses of impinging jet devices for heat transfer are described, with a focus on cooling applications within turbine systems. Numerical simulation techniques and results are described, and the relative strengths and drawbacks of the k-ε,k-ω, Reynolds stress model, algebraic stress models, shear stress transport, and v2f turbulence models for impinging jet flow and heat transfer are compared. Select model equations are provided as well as quantitative assessments of model errors and judgments of model suitability.

Numerical Simulation of Turbine Blade Boundary Layer and Heat Transfer and Assessment of Turbulence Models

1997 ◽  
Vol 119 (4) ◽  
pp. 794-801 ◽  
Author(s):  
J. Luo ◽  
B. Lakshminarayana
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Bypass Transition ◽  
Boundary Layer Development ◽  
Low Reynolds ◽  
Layer Development

The boundary layer development and convective heat transfer on transonic turbine nozzle vanes are investigated using a compressible Navier–Stokes code with three low-Reynolds-number k–ε models. The mean-flow and turbulence transport equations are integrated by a four-stage Runge–Kutta scheme. Numerical predictions are compared with the experimental data acquired at Allison Engine Company. An assessment of the performance of various turbulence models is carried out. The two modes of transition, bypass transition and separation-induced transition, are studied comparatively. Effects of blade surface pressure gradients, free-stream turbulence level, and Reynolds number on the blade boundary layer development, particularly transition onset, are examined. Predictions from a parabolic boundary layer code are included for comparison with those from the elliptic Navier–Stokes code. The present study indicates that the turbine external heat transfer, under real engine conditions, can be predicted well by the Navier–Stokes procedure with the low-Reynolds-number k–ε models employed.

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