Numerical Comparisons of Heat Transfer From a Single Jet Emanating From a Slot Nozzle Impinging on an Isothermal Plate

2019 ◽  
Author(s):  
Cristian Tibabisco ◽  
Salvador Vargas-Díaz ◽  
Samir A. Salamah
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Stagnation Point ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Thermal Design ◽  
Navier Stokes ◽  
Reynolds Average Navier Stokes ◽  
Single Jet ◽  
Reynolds Average

Abstract Impingement jets are used in different cooling applications where it is required to remove large amounts of heat. Heat transfer in the stagnation point for a single jet impinging on an isothermal plate is investigated with four turbulence models. Two models are RANS (Reynolds Average Navier-Stokes): Transition SST and Transition κ–κl–ω. The other two models are URANS (Unsteady Reynolds Average Navier-Stokes): SAS and DES-SST. This paper explores the best turbulence model for thermal design and cooling purposes. Results are validated with experimental data reported by Gardon & Akfirat. These four turbulence models are available in the commercial CFD software package ANSYS FLUENT 18.1. Special attention is paid to the heat transfer in the impingement region through evaluation of Nusselt number in the stagnation point. Different dimensionless nozzle-to-plate distances are considered in this work (z/b = 14 to z/b = 40), and two different Reynolds numbers are used Re = 11,000 y Re = 22,000. Three turbulence models are within reasonable accuracy (10%) of the experimental data, but some turbulence models have problems with convergence and grid independence, especially the URANS models. Based on these results, the best turbulence model for applications in heating and cooling systems where impingement heat transfer is critical is the Transition κ–κl–ω.

Computational Fluid Dynamics Modeling of Mixed Convection Flows in Building Enclosures

2013 ◽  
Author(s):  
Alexander Kayne ◽  
Ramesh Agarwal
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Mixed Convection ◽  
Turbulence Model ◽  
Numerical Algorithm ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Flow And Heat Transfer

In recent years Computational Fluid Dynamics (CFD) simulations are increasingly used to model the air circulation and temperature environment inside the rooms of residential and office buildings to gain insight into the relative energy consumptions of various HVAC systems for cooling/heating for climate control and thermal comfort. This requires accurate simulation of turbulent flow and heat transfer for various types of ventilation systems using the Reynolds-Averaged Navier-Stokes (RANS) equations of fluid dynamics. Large Eddy Simulation (LES) or Direct Numerical Simulation (DNS) of Navier-Stokes equations is computationally intensive and expensive for simulations of this kind. As a result, vast majority of CFD simulations employ RANS equations in conjunction with a turbulence model. In order to assess the modeling requirements (mesh, numerical algorithm, turbulence model etc.) for accurate simulations, it is critical to validate the calculations against the experimental data. For this purpose, we use three well known benchmark validation cases, one for natural convection in 2D closed vertical cavity, second for forced convection in a 2D rectangular cavity and the third for mixed convection in a 2D square cavity. The simulations are performed on a number of meshes of different density using a number of turbulence models. It is found that k-epsilon two-equation turbulence model with a second-order algorithm on a reasonable mesh gives the best results. This information is then used to determine the modeling requirements (mesh, numerical algorithm, turbulence model etc.) for flows in 3D enclosures with different ventilation systems. In particular two cases are considered for which the experimental data is available. These cases are (1) air flow and heat transfer in a naturally ventilated room and (2) airflow and temperature distribution in an atrium. Good agreement with the experimental data and computations of other investigators is obtained.

Heat Transfer and Hydraulic Resistance in Turbulent Flow in Vertical Round Tubes At Supercritical Pressures. Part 1. Results From Numerical Simulations Using Algebraic Turbulent Viscosity Models

2020 ◽  
Author(s):  
Georgii Glebovich Yankov ◽  
Vladimir Kurganov ◽  
Yury Zeigarnik ◽  
Irina Maslakova
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbulent Flow ◽  
Hydraulic Resistance ◽  
Turbulent Viscosity ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Heating And Cooling ◽  
Prediction Techniques ◽  
Vertical Tubes

Abstract The review of numerical studies on supercritical pressure (SCP) coolants heat transfer and hydraulic resistance in turbulent flow in vertical round tubes based on Reynolds-averaged Navier-Stokes (RANS) equations and different models for turbulent viscosity is presented. The paper is the first part of the general analysis, the works based on using algebraic turbulence models of different complexity are considered in it. The main attention is paid to Petukhov-Medvetskaya and Popov et al. models. They were developed especially for simulating heat transfer in tubes of the coolants with significantly variable properties (droplet liquids, gases, SCP fluids) under heating and cooling conditions. These predictions were verified on the entire reliable experimental data base. It is shown that in the case of turbulent flow in vertical round tubes these models make it possible predicting heat transfer and hydraulic resistance characteristics of SCP flows that agree well with the existed reliable experimental data on normal and certain modes of deteriorated heat transfer, if significant influence of buoyancy and radical flow restructuring are absent. For the more complicated cases than a flow in round vertical tubes, as well as for the case of rather strong buoyancy effect, more sophisticated prediction techniques must be applied. The state-of-the-art of these methods and the problems of their application are considered in the Part II of the analysis.

scholarly journals Prediction of Airfoil Stall Based on a Modified k−v2¯−ω Turbulence Model

Mathematics ◽  
2022 ◽  
Vol 10 (2) ◽  
pp. 272
Author(s):  
Chenyu Wu ◽  
Haoran Li ◽  
Yufei Zhang ◽  
Haixin Chen
Keyword(s):  
Experimental Data ◽  
Shear Layer ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Trailing Edge ◽  
Naca0012 Airfoil ◽  
Separated Shear Layer ◽  
Non Equilibrium

The accuracy of an airfoil stall prediction heavily depends on the computation of the separated shear layer. Capturing the strong non-equilibrium turbulence in the shear layer is crucial for the accuracy of a stall prediction. In this paper, different Reynolds-averaged Navier–Stokes turbulence models are adopted and compared for airfoil stall prediction. The results show that the separated shear layer fixed k−v2¯−ω (abbreviated as SPF k−v2¯−ω) turbulence model captures the non-equilibrium turbulence in the separated shear layer well and gives satisfactory predictions of both thin-airfoil stall and trailing-edge stall. At small Reynolds numbers (Re~105), the relative error between the predicted CL,max of NACA64A010 by the SPF k−v2¯−ω model and the experimental data is less than 3.5%. At high Reynolds numbers (Re~106), the CL,max of NACA64A010 and NACA64A006 predicted by the SPF k−v2¯−ω model also has an error of less than 5.5% relative to the experimental data. The stall of the NACA0012 airfoil, which features trailing-edge stall, is also computed by the SPF k−v2¯−ω model. The SPF k−v2¯−ω model is also applied to a NACA0012 airfoil, which features trailing-edge stall and an error of CL relative to the experiment at CL>1.0 is smaller than 3.5%. The SPF k−v2¯−ω model shows higher accuracy than other turbulence models.

scholarly journals Analysis of Applicability of CFD Numerical Studies Applied to Problem When Pump Working as Turbine

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2134
Author(s):  
Frank Plua ◽  
Victor Hidalgo ◽  
P. Amparo López-Jiménez ◽  
Modesto Pérez-Sánchez
Keyword(s):  
Turbulence Models ◽  
Experimental Tests ◽  
Navier Stokes ◽  
Variable Speed ◽  
Reynolds Average Navier Stokes ◽  
Academic Literature ◽  
Numerical Studies ◽  
Speed Rotation ◽  
Computational Fluid Dynamics Cfd ◽  
Reynolds Average

The present research depicts an analysis of the implementation of computational fluid dynamics (CFD) in the study of pumps such as turbines and PATs. To highlight the benefits of CFDs for PAT studies, results from both experimental tests have been compared to better understand the reproduction error phenomena. For this, data analysis used in successful models has been applied to determine variables and parameters, and to report a low relative error. The results show that most of the studies focused on fixed speed rotation with some cases of variable speed rotation. Furthermore, there is not enough information in the academic literature for PAT of axial and mixed flows with fixed and variable speed. Finally, turbulence models based on Reynolds average Navier–Stokes (RANS) have been used to simulate PATs with fixed speed rotation in most cases.

scholarly journals Prediction of Turbine Blade Passage Heat Transfer Using a Zero and a Two-Equation Turbulence Model

1994 ◽  
Author(s):  
Ali A. Ameri ◽  
Andrea Arnone
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Algebraic Model ◽  
Equation Model ◽  
Accurate Solution ◽  
Bypass Transition ◽  
Transfer Rates ◽  
Blade Passage

Predictions of the heat transfer rates on the hot surfaces of a turbine cascade blade passage as influenced by the turbulence models was examined. A zero equation turbulence model supplemented by a bypass transition model and a two equation low Reynolds number model were chosen for this study. The experimental data of Graziani et. al. were used for comparison. The comparisons suggest that at least for the experimental data considered in this work the use of a two-equation model does not provide an overall more accurate solution than the zero equation model. This conclusion is strengthened if one takes into account the relative economy of computations with the algebraic model.

scholarly journals Experimental and numerical investigation of non-submerged flow under a sluice gate

2015 ◽  
Vol 47 (3) ◽  
pp. 187-201 ◽  
Author(s):  
Adam Kiczko ◽  
Janusz Kubrak ◽  
Elżbieta Kubrak
Keyword(s):  
Experimental Data ◽  
Numerical Solution ◽  
Numerical Investigation ◽  
Potential Field ◽  
Complex Form ◽  
Navier Stokes ◽  
Energy Losses ◽  
Sluice Gate ◽  
Reynolds Average Navier Stokes ◽  
Reynolds Average

Abstract The problem of sluice gate flow is analyzed using two models: a simplified one, derived according to the concept of the Potential Field (PF), and a more complex form, based on the Reynolds Average Navier-Stokes (RANS) equations. The numerical solution is compared with experimental data, including measurements performed by authors and results acquired from literature. Despite its simplicity, the PF model provides a satisfactory agreement with the measurements. The slightly worse performance of the RANS model comes from an overestimation of energy losses.

Effects of 3-D Local Unsteadiness on Heat Transfer Prediction in Turbulated Passages

2003 ◽  
Author(s):  
Pamela A. McDowell ◽  
William D. York ◽  
D. Keith Walters ◽  
James H. Leylek
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbulence Model ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Successful Outcome ◽  
Small Scale ◽  
Cross Sectional ◽  
Fully Implicit

A newly developed unsteady turbulence model was used to predict heat transfer in a turbulated passage typical of turbine airfoil cooling applications. Comparison of fullyconverged computational solutions to experimental measurements reveal that accurate prediction of heat transfer coefficient requires the effects of local small-scale unsteadiness to be captured. Validation was accomplished through comparison of the time- and area-averaged Nusselt number on the passage wall between adjacent ribs with experimental data from the open literature. The straight channel had a square cross-sectional area with multiple rows of staggered and rounded-edge ribs on opposite walls that were orthogonal to the flow. Simulations were run for Reynolds numbers of 5500, 16500, and 25000. Computational solutions were obtained on a multi-block, multi-topology, unstructured, and adaptive grid, using a pressure-correction based, fully-implicit Navier-Stokes solver. The computational results include two-dimensional (2-D) and three-dimensional (3-D) steady and unsteady simulations with viscous sublayers resolved (y+ ≤ 1) on all the walls in every case. Turbulence closure was obtained using a new turbulence model developed in-house for the unsteady simulations, and a realizable k-ε turbulence model was used for the steady simulations. The results obtained from the unsteady simulations show greatly improved agreement with the experimental data, especially at realistically high Reynolds numbers. The key 3-D physics mechanisms responsible for the successful outcome include: (1) shear layer roll-up over the turbulators; (2) recirculation zones both upstream and downstream of the rib faces; and (3) reattachment regions between each rib pair. Results from the unsteady case are superior to those of the steady because they capture the aforementioned mechanisms, and therefore more accurately predict the heat transfer.

scholarly journals Heat Transfer on a Film-Cooled Rotating Blade Using a Two-Equation Turbulence Model

1998 ◽  
Vol 4 (3) ◽  
pp. 201-216 ◽  
Author(s):  
Vijay K. Garg
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Leading Edge ◽  
Equation Model ◽  
Tip Clearance ◽  
Suction Surface ◽  
Pressure Surface ◽  
Rotating Blade

A three-dimensional Navier–Stokes code has been used to compare the heat transfer coefficient on a film-cooled, rotating turbine blade. The blade chosen is the ACE rotor with five rows containing 93 film cooling holes covering the entire span. This is the only filmcooled rotating blade over which experimental data is available for comparison. Over 2.278 million grid points are used to compute the flow over the blade including the tip clearance region, using Coakley'sq-ωturbulence model. Results are also compared with those obtained by Garg and Abhari (1997) using the zero-equation Baldwin-Lomax (B-L) model. A reasonably good comparison with the experimental data is obtained on the suction surface for both the turbulence models. At the leading edge, the B-L model yields a better comparison than theq-ωmodel. On the pressure surface, however, the comparison between the experimental data and the prediction from either turbulence model is poor. A potential reason for the discrepancy on the pressure surface could be the presence of unsteady effects due to stator-rotor interaction in the experiments which are not modeled in the present computations. Prediction using the two-equation model is in general poorer than that using the zero-equation model, while the former requires at least 40% more computational resources.

Analysis and Modifications of Turbulence Models for Wind Turbine Wake Simulations in Atmospheric Boundary Layers

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Enrico G. A. Antonini ◽  
David A. Romero ◽  
Cristina H. Amon
Keyword(s):  
Experimental Data ◽  
Velocity Field ◽  
Wind Turbine ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Wind Farms ◽  
Navier Stokes ◽  
Stress Models ◽  
Turbine Wake ◽  
Wind Turbine Wake

Computational fluid dynamics (CFD) simulations of wind turbine wakes are strongly influenced by the choice of the turbulence model used to close the Reynolds-averaged Navier-Stokes (RANS) equations. A wrong choice can lead to incorrect predictions of the velocity field characterizing the wind turbine wake and, consequently, to an incorrect power estimation for wind turbines operating downstream. This study aims to investigate the influence of different turbulence models, namely the k–ε, k–ω, SSTk–ω, and Reynolds stress models (RSM), on the results of CFD wind turbine simulations. Their influence was evaluated by comparing the CFD results with the publicly available experimental measurements of the velocity field and turbulence quantities from the Sexbierum and Nibe wind farms. Consistent turbulence model constants were proposed for atmospheric boundary layer (ABL) and wake flows according to previous literature and appropriate experimental observations, and modifications of the derived turbulence model constants were also investigated in order to improve agreement with experimental data. The results showed that the simulations using the k–ε and k–ω turbulence models consistently overestimated the velocity and turbulence quantities in the wind turbine wakes, whereas the simulations using the shear-stress transport (SST) k–ω and RSMs could accurately match the experimental data. Results also showed that the predictions from the k–ε and k–ω turbulence models could be improved by using the modified set of turbulence coefficients.

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