Modular Turbulence Modeling Applied to an Engine Intake

2013 ◽  
Vol 136 (5) ◽  
Author(s):  
Ugochukwu R. Oriji ◽  
Paul G. Tucker
Keyword(s):  
Surface Roughness ◽  
Turbulence Modeling ◽  
Fluid Dynamic ◽  
Navier Stokes ◽  
Test Cases ◽  
Laminar Separation ◽  
Streamline Curvature ◽  
Favorable Pressure Gradient ◽  
Flow Features ◽  
The One

The one equation Spalart–Allmaras (SA) turbulence model in an extended modular form is presented. It is employed for the prediction of crosswind flow around the lip of a 90 deg sector of an intake with and without surface roughness. The flow features around the lip are complex. There exists a region of high streamline curvature. For this, the Richardson number would suggest complete degeneration to laminar flow. Also, there are regions of high favorable pressure gradient (FPG) sufficient to laminarize a turbulent boundary layer (BL). This is all terminated by a shock and followed by a laminar separation. Under these severe conditions, the SA model is insensitive to capturing the effects of laminarization and the reenergization of eddy viscosity. The latter promotes the momentum transfer and correct reattachment prior to the fan face. Through distinct modules, the SA model has been modified to account for the effect of laminarization and separation induced transition. The modules have been implemented in the Rolls-Royce HYDRA computational fluid dynamic (CFD) solver. They have been validated over a number of experimental test cases involving laminarization and also surface roughness. The validated modules are finally applied in unsteady Reynolds-averaged Navier–Stokes (URANS) mode to flow around an engine intake and comparisons made with measurements. Encouraging agreement is found and hence advances made towards a more reliable intake design framework.

Modular Turbulence Modelling Applied to an Engine Intake

2013 ◽  
Author(s):  
Ugochukwu R. Oriji ◽  
Paul G. Tucker
Keyword(s):  
Surface Roughness ◽  
Richardson Number ◽  
Eddy Viscosity ◽  
Fluid Dynamic ◽  
Test Cases ◽  
Laminar Separation ◽  
Streamline Curvature ◽  
Flow Features ◽  
Unsteady Rans ◽  
The One

The one equation Spalart Allamaras (SA) turbulence model in an extended modular form is employed for the prediction of cross wind flow around the lip of a 90 degree sector of an intake with and without surface roughness. The flow features around the lip are complex. There exists a region of high streamline curvature. For this the Richardson number would suggest complete degeneration to laminar flow. Also there are regions of high favourable pressure gradient (FPG) sufficient to laminarize a turbulent boundary layer (BL). This is all terminated by a shock and followed by a laminar separation. Under these severe conditions, the SA model is insensitive to capturing the effects of laminarization and the reenergization of eddy viscosity which promotes the momentum transfer and correct reattachment prior to the fan face. Through distinct modules, the SA model has been modified to account for the effect of laminarization and separation induced transition. The SA modules have been implemented in Rolls-Royce HYDRA Computational Fluid Dynamic (CFD) solver. They have been validated over a number of experimental test cases involving laminarization and also surface roughness. The validated modules are finally applied in unsteady RANS mode to flow around an engine intake and comparisons made with measurements. Encouraging agreement is found and hence advances made towards a more reliable intake design framework.

An Aerodynamic Investigation of an Isolated Stationary Formula 1 Wheel Assembly

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
John Axerio-Cilies ◽  
Emin Issakhanian ◽  
Juan Jimenez ◽  
Gianluca Iaccarino
Keyword(s):  
Experimental Data ◽  
Large Scale ◽  
Turbulence Modeling ◽  
Cross Flow ◽  
Vortex Pair ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Flow Features ◽  
Large Scale Flow ◽  
Flow Blockage

The flowfield around a 60% scale stationary Formula 1 tire in contact with the ground in a closed wind tunnel at a Reynolds number of 500,000 was computationally examined in order to assess the accuracy of different turbulence modeling techniques and confirm the existence of large scale flow features. A simplified and replica tire model that includes all brake components was tested to determine the sensitivity of the wake to cross flow within the tire hub along with the flow blockage caused by the brake assembly. The results of steady and unsteady Reynolds averaged Navier-Stokes (URANS) equations and a large eddy simulation (LES) were compared with the experimental data. The LES closure and the RANS closure that accounted for unsteadiness with low eddy viscosity (unsteady kω-SST) matched closest to the experimental data both in point wise velocity comparisons along with location and intensity of the strong counter-rotating vortex pair dominating the far wake of the tire.

scholarly journals Boundary Layer and Navier-Stokes Analysis of a NASA Controlled-Diffusion Compressor Blade

1990 ◽  
Author(s):  
Y. K. Ho ◽  
G. J. Walker ◽  
P. Stow
Keyword(s):  
Boundary Layer ◽  
Turbulence Modeling ◽  
Separation Bubble ◽  
Leading Edge ◽  
Adverse Pressure Gradient ◽  
Compressor Blade ◽  
Navier Stokes ◽  
Laminar Separation ◽  
Controlled Diffusion ◽  
Pressure Distributions

Performance calculations for a NASA controlled-diffusion compressor blade have been carried out with a coupled inviscid-boundary layer code and a time-marching Navier-Stokes solver. Comparisons with experimental test data highlight and explain the strengths and limitations of both these computational methods. The boundary layer code gives good results at and near design conditions. Loss predictions however deteriorated at off-design incidences. This is mainly due to a problem with leading edge laminar separation bubble modelling; coupled with an inability of the calculations to grow the turbulent boundary layer at a correct rate in a strong adverse pressure gradient. Navier-Stokes loss predictions on the other hand are creditable throughout the whole incidence range, except at extreme positive incidence where turbulence modeling problems similar to those of the coupled boundary layer code are observed. The main drawback for the Navier-Stokes code is the slow rate of convergence for these low Mach number cases. Plans are currently under review to address this problem. Both codes give excellent predictions of the blade surface pressure distributions for all the cases considered.

scholarly journals The effect of volute surface roughness on the performance of automotive turbocharger turbines

2017 ◽  
Vol 1 ◽  
pp. 3FLVC0
Author(s):  
Andreas Lintz
Keyword(s):  
Surface Roughness ◽  
Cross Sections ◽  
Pressure Loss ◽  
Navier Stokes ◽  
Test Cases ◽  
Actual Surface ◽  
Turbine Efficiency ◽  
Internal Surfaces ◽  
Potential Benefits ◽  
Additional Costs

Abstract The roughness level of the turbine housing’s internal surfaces can affect the total pressure loss, and hence the efficiency, of turbine stages for automotive turbochargers significantly. The actual surface roughness achieved in the housing hardware depends on the manufacturing process. Improving the volute surface quality will in most cases be more expensive. The potential benefits in turbine efficiency therefore have to be balanced with the additional costs. In the present article, the aerodynamic effects due to changes of volute surface roughness are assessed. Pressure loss measurements in simple pipes are conducted in order to calibrate a computational fluid dynamics (CFD) sand grain roughness model against measured roughness values. Two test cases involving flow simulations of the complete turbine stage are presented in order to validate the calibrated model and to show that Reynolds-averaged Navier Stokes (RANS) CFD simulations are generally able to predict the effects of surface roughness on the turbine performance. The results of the test cases show a significant reduction in turbine efficiency with increased volute roughness levels. As expected, the sensitivity of efficiency due to changes in surface roughness of the volute is largest in areas of high near-wall velocity, i.e., at the volute exducer and in the small volute cross-sections close to the tongue.

scholarly journals Conjugate Heat Transfer Predictions for Subcooled Boiling Flow in a Horizontal Channel Using a Volume-of-Fluid Framework

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
M. Langari ◽  
Z. Yang ◽  
J. F. Dunne ◽  
S. Jafari ◽  
J.-P. Pirault ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbulence Modeling ◽  
Fluid Dynamic ◽  
Computational Cost ◽  
Thermal Conditions ◽  
Nucleate Boiling ◽  
Volume Of Fluid ◽  
Navier Stokes ◽  
Mass Generation

Abstract The accuracy of computational fluid dynamic (CFD)-based heat transfer predictions have been examined of relevance to liquid cooling of IC engines at high engine loads where some nucleate boiling occurs. Predictions based on (i) the Reynolds Averaged Navier-Stokes (RANS) solution and (ii) large eddy simulation (LES) have been generated. The purpose of these simulations is to establish the role of turbulence modeling on the accuracy and efficiency of heat transfer predictions for engine-like thermal conditions where published experimental data are available. A multiphase mixture modeling approach, with a volume-of-fluid interface-capturing method, has been employed. To predict heat transfer in the boiling regime, the empirical boiling correlation of Rohsenow is used for both RANS and LES. The rate of vapor-mass generation at the wall surface is determined from the heat flux associated with the evaporation phase change. Predictions via CFD are compared with published experimental data showing that LES gives only slightly more accurate temperature predictions compared to RANS but at substantially higher computational cost.

scholarly journals Analysis of Aspect Ratio Effects on Transonic Rotor Performance Using a 3D Viscous Solver

1998 ◽  
Author(s):  
Cecil R. Buchanan ◽  
Paul R. Emmerson ◽  
Michael Spruce
Keyword(s):  
Aspect Ratio ◽  
Numerical Study ◽  
Navier Stokes ◽  
Test Cases ◽  
Compressor Rotor ◽  
Aspect Ratios ◽  
Radial Profiles ◽  
Ratio Change ◽  
The One ◽  
Good Agreement

This paper presents the results of a numerical study into the effects of aspect ratio on compressor rotor performance. The test cases studied are NASA rotors 37 and 38, which have aspect ratios of 1.19 and 1.63 respectively. A 3D, single-passage steady flow Navier-Stokes solver was used to predict complete performance characteristics, including the numerical instability point, for both rotors. The predictions are generally in good agreement with the test data (characteristics, radial profiles and rotor over tip measurements) at all conditions modelled for rotor 37. The performance for rotor 38 is overpredicted, with slightly less than half of the measured performance difference between the two rotors being captured. The effect of a pure aspect ratio change (divorced from the rotor inlet to exit area changes present in the rotor 37/38 comparisons) was also investigated, and a case with an aspect ratio double that of rotor 37 was also modelled. The results indicated that the code predicted little effect on rotor performance due to an aspect ratio change alone (from 1.19 to 2.38). This is surprising and it raises doubts about the ability of current codes (or at least the one used in the study) to predict this important aspect of a compressor design adequately.

Numerical Studies on Cavitation and Surface Roughness

2019 ◽  
Vol 793 ◽  
pp. 79-84 ◽  
Author(s):  
Jithin Ambarayil Joy ◽  
Vijayakumar Mathaiyan ◽  
Muhammad Sajjad ◽  
Dong Won Jung
Keyword(s):  
Biological Sciences ◽  
Surface Roughness ◽  
Parametric Analysis ◽  
Smooth Surface ◽  
Material Surface ◽  
Cavitation Damage ◽  
Numerical Studies ◽  
Flow Features ◽  
The One ◽  
Topical Interest

The study of cavitation is of topical interest in both physical and biological sciences. The surface roughness changes the effect of cavitation on a material surface. Due to cavitation, the material with low surface roughness value has relatively more damage, when compared to the one with higher value. In this paper, preliminary numerical studies are carried on cavitation and surface roughness. As a part of the code validation and calibration, the numerically predicted boundary-layer blockage at the Sanal flow choking condition for the channel flow is verified using the closed-form analytical model of V.R. Sanal Kumar et al. (AIP Advances, 8, 025315, 2018) at various surface roughness and found excellent agreement with the exact solution. Parametric analytical studies are carried out for examining the flow features at two different surface roughness and turbulence levels. We noticed that the wavy surface with small waves increases the Nussle number, therefore it is also considered for parametric analysis. Considering the defect-free smooth surface material, we presumed that the cavitation damage in the smooth surface is more than the rough surface because the smooth surface can generate more micro bubbles. These micro bubbles grow into macro bubbles which in turn results in cavitation. This study is a pointer towards for formulating various industrial topics with fluid-structural interaction problems for getting plausible solutions for meeting the needs of various industries.

Effect of rocket exhaust of canisterized missile on adjoining launching system

2016 ◽  
Vol 231 (11) ◽  
pp. 2085-2097 ◽  
Author(s):  
MSR Chandra Murty ◽  
PK Sinha ◽  
D Chakraborty
Keyword(s):  
Stokes Equations ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Test Configuration ◽  
Instantaneous Position ◽  
Flow Features ◽  
Scale Down ◽  
Parametric Studies

Transient numerical simulations are carried out to study missile motion in a vertical launch system and to estimate the effect of missile exhaust in the adjoining launch structure. Three-dimensional Navier–Stokes equations along with k–ɛ turbulence model and species transport equations are solved using commercial computational fluid dynamics software. Dynamic grid movement is adopted and one degree of freedom trajectory equations are integrated with the computational fluid dynamic solver to obtain the instantaneous position of the missile. Multi-zone grid generation approach with sliding interface method through layering technique is adopted to address the changing boundary problem. The computational methodology is applied to study the missile motion in a scale-down test configuration as well as in the flight condition. The computations capture all essential flow features of test and flight conditions in active cell as well as in adjacent cells. Parametric studies are conducted to study the effect geometrical features and measurement uncertainty in the input data. Computed pressures in the adjacent cells in the launch system match better (∼12%) with the experimental and flight results compared to distant cells.

Application of the v2-f Turbulence Model to Turbomachinery Configurations

2007 ◽  
Author(s):  
B. Tartinville ◽  
E. Lorrain ◽  
Ch. Hirsch
Keyword(s):  
Heat Transfer ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Critical Issue ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Test Cases ◽  
Laminar To Turbulent Transition ◽  
Turbulent Transition ◽  
Flow Features

Enhancing the representation of turbulence processes is a critical issue for CFD codes devoted to turbomachinery industry. Though more complex methods are available, Reynolds-Averaged Navier-Stokes models are widely used in the daily design process. Therefore, there is a constant need for improving eddy-viscosity based turbulence models. The present work aims at investigating the capabilities of the v2-f turbulence model for turbomachinery applications. Three types of flow features that are of importance for such applications are investigated in details: heat transfer, secondary flows, and laminar to turbulent transition. From a series of test cases, it appears that the v2-f turbulence model is specially adapted for heat transfer applications and shows potentialities in predicting laminar to turbulent transition.

scholarly journals NUMERICAL INVESTIGATION OF THE INFLUENCE OF SURFACE ROUGHNESS ON CONVECTIVE HEAT TRANSFER AT AIRFOIL ICING PROCESS

2018 ◽  
Vol 40 (2) ◽  
pp. 65-71
Author(s):  
A. A. Prykhodko ◽  
S. V. Alekseyenko
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Stokes Equations ◽  
Rough Wall ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Differential Model ◽  
The One

The technique of the processes of investigating of convective heat transfer determining in the problems of icing of aerodynamic surfaces on the basis of the solution of the Reynolds-averaged Navier- Stokes equations and the one-parameter Spalart-Allmaras turbulence differential model with correction for a rough wall is presented. A methodology that allowed to simulate airfoils icing processes taking into account the ice surface roughness is presented. For the description of the external air-droplet flow a model of interpenetrating media was used. For the description of the ice growing process the method of surface control volumes using the methodology of determining the convective heat transfer based on the solution of the Navier-Stokes equations and the one-parameter differential Spalart-Allmaras turbulence model with a correction for a rough wall were used. Verification was performed by comparing the calculations results with the data obtained with the help of known semiempirical relationships. The proposed approach, unlike existing methods, will allow us to begin solving problems in a three-dimensional statement, with a rather complex geometry, in the presence of transonic regions in the airflow, and also to determine the aerodynamic characteristics of streamlined bodies with rough ice accretions. References 15, figures 3.

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