scholarly journals An Arbitrary Hybrid Turbulence Modeling Approach for Efficient and Accurate Automotive Aerodynamic Analysis and Design Optimization

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 407
Author(s):  
Saule Maulenkul ◽  
Kaiyrbek Yerzhanov ◽  
Azamat Kabidollayev ◽  
Bagdaulet Kamalov ◽  
Sagidolla Batay ◽  
...  
Keyword(s):  
Flow Field ◽  
Design Optimization ◽  
Automotive Industry ◽  
Turbulence Modeling ◽  
Turbulence Models ◽  
Analysis And Design ◽  
Eddy Simulation ◽  
Gradient Based ◽  
Automotive Aerodynamics ◽  
Single Flow

The demand in solving complex turbulent fluid flows has been growing rapidly in the automotive industry for the last decade as engineers strive to design better vehicles to improve drag coefficients, noise levels and drivability. This paper presents the implementation of an arbitrary hybrid turbulence modeling (AHTM) approach in OpenFOAM for the efficient simulation of common automotive aerodynamics with unsteady turbulent separated flows such as the Kelvin–Helmholtz effect, which can also be used as an efficient part of aerodynamic design optimization (ADO) tools. This AHTM approach is based on the concept of Very Large Eddy Simulation (VLES), which can arbitrarily combine RANS, URANS, LES and DNS turbulence models in a single flow field depending on the local mesh refinement. As a result, the design engineer can take advantage of this unique and highly flexible approach to tailor his grid according to his design and resolution requirements in different areas of the flow field over the car body without sacrificing accuracy and efficiency at the same time. This paper presents the details of the implementation and careful validation of the AHTM method using the standard benchmark case of the Ahmed body, in comparison with some other existing models, such as RANS, URANS, DES and LES, which shows VLES to be the most accurate among the five examined. Furthermore, the results of this study demonstrate that the AHTM approach has the flexibility, efficiency and accuracy to be integrated with ADO tools for engineering design in the automotive industry. The approach can also be used for the detailed study of highly complex turbulent phenomena such as the Kelvin–Helmholtz instability commonly found in automotive aerodynamics. Currently, the AHTM implementation is being integrated with the DAFoam for gradient-based multi-point ADO using an efficient adjoint solver based on a Sparse Nonlinear optimizer (SNOPT).

scholarly journals Investigation of the velocity field downstream of a benchmark vent using numerical simulation and hot-wire anemometry

2019 ◽  
Vol 213 ◽  
pp. 02076
Author(s):  
Jan Sip ◽  
Frantisek Lizal ◽  
Jakub Elcner ◽  
Jan Pokorny ◽  
Miroslav Jicha
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Velocity Field ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Turbulence Models ◽  
Hot Wire ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Precise Prediction

The velocity field in the area behind the automotive vent was measured by hot-wire anenemometry in detail and intensity of turbulence was calculated. Numerical simulation of the same flow field was performed using Computational fluid dynamics in commecial software STAR-CCM+. Several turbulence models were tested and compared with Large Eddy Simulation. The influence of turbulence model on the results of air flow from the vent was investigated. The comparison of simulations and experimental results showed that most precise prediction of flow field was provided by Spalart-Allmaras model. Large eddy simulation did not provide results in quality that would compensate for the increased computing cost.

scholarly journals Comparative Study on CFD Turbulence Models for the Flow Field in Air Cooled Radiator

Processes ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 1687
Author(s):  
Chao Yu ◽  
Xiangyao Xue ◽  
Kui Shi ◽  
Mingzhen Shao ◽  
Yang Liu
Keyword(s):  
Flow Field ◽  
Transient Flow ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Compartment Model ◽  
Navier Stokes ◽  
Engine Compartment ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Relevant Calculation

This paper compares the performances of three Computational Fluid Dynamics (CFD) turbulence models, Reynolds Average Navier-Stokes (RANS), Detached Eddy Simulation (DES), and Large Eddy Simulation (LES), for simulating the flow field of a wheel loader engine compartment. The distributions of pressure fields, velocity fields, and vortex structures in a hybrid-grided engine compartment model are analyzed. The result reveals that the LES and DES can capture the detachment and breakage of the trailing edge more abundantly and meticulously than RANS. Additionally, by comparing the relevant calculation time, the feasibility of the DES model is proved to simulate the three-dimensional unsteady flow of engine compartment efficiently and accurately. This paper aims to provide a guiding idea for simulating the transient flow field in the engine compartment, which could serve as a theoretical basis for optimizing and improving the layout of the components of the engine compartment.

The Use of Solution Adaptive Grid for Modeling Small Scale Turbulent Structures

2005 ◽  
Vol 127 (5) ◽  
pp. 936-944 ◽  
Author(s):  
G. de With ◽  
A. E. Holdø
Keyword(s):  
Flow Field ◽  
Turbulence Modeling ◽  
Flow Region ◽  
Adaptive Methods ◽  
Adaptive Grid ◽  
Small Scale ◽  
Free Shear Layer ◽  
Turbulent Structures ◽  
Eddy Simulation ◽  
Computationally Intensive

The use of large eddy simulation (LES) is computationally intensive and various studies demonstrated the considerable range of vortex scales to be resolved in an LES type of simulation. The purpose of this study is to investigate the use of a dynamic grid adaptation (DGA) algorithm. Despite many developments related to adaptive methods and adaptive grid strategies, the use of DGA in the context of turbulence modeling is still not well understood, and various profound problems with DGA in relation to turbulence modeling are still present. The work presented in this paper focuses on the numerical modeling of flow around a circular cylinder in the sub-critical flow regime at a Reynolds number of 3.9∙103. LES simulations with conventional mesh and DGA have been performed with various mesh sizes, refinement criteria and re-meshing frequency, to investigate the effects of re-meshing on the flow field prediction. The results indicate that the turbulent flow field is sensitive to modifications in the mesh and re-meshing frequency, and it is suggested that the re-meshing in the unsteady flow region is affecting the onset of small scale flow motions in the free shear layer.

A Time-Parallel CFD Approach for Unsteady Combustor Flow Analysis and Design Optimization

2012 ◽  
Author(s):  
Moresh J. Wankhede ◽  
Neil W. Bressloff ◽  
Andy J. Keane
Keyword(s):  
Flow Field ◽  
Domain Decomposition ◽  
Design Optimization ◽  
Cfd Simulation ◽  
Simulation Method ◽  
Spatial Domain ◽  
Parallel Simulation ◽  
Analysis And Design ◽  
Temporal Domain ◽  
Parallel Cfd

Computational fluid dynamics (CFD) simulations to predict and visualize the reacting flow dynamics inside a combustor require fine resolution over the spatial and temporal domain, making them computationally very expensive. The traditional time-serial approach for setting up a parallel combustor CFD simulation is to divide the spatial domain between computing nodes and treat the temporal domain sequentially. However, it is well known that spatial domain decomposition techniques are not very efficient especially when the spatial dimension (or mesh count) of the problem is small and a large number of nodes are used, as the communication costs due to data parallelism becomes significant per iteration. Hence, temporal domain decomposition has some attraction for unsteady simulations, particularly on relatively coarse spatial meshes. The purpose of this study is two-fold: (i), to develop a time-parallel CFD simulation method and apply it to solve the transient reactive flow-field in a combustor using an unsteady Reynolds-averaged Navier Stokes (URANS) formulation in the commercial CFD code FLUENT™ and (ii) to investigate its benefits relative to a time-serial approach and its potential use for combustor design optimization. The results show that the time-parallel simulation method correctly captures the unsteady combustor flow evolution but, with the applied time-parallel formulation, a clear speed-up advantage, in terms of wall-clock time, is not obtained relative to the time-serial approach. However, it is clear that the time-parallel simulation method provides multiple stages of transient combustor flow-field solution data whilst converging towards a final converged state. The availability of this resulting data could be used to seed multiple levels of fidelity within the framework of a multi-fidelity co-Kriging based design optimization strategy. Also, only a single simulation would need to be setup from which multiple fidelities are available.

scholarly journals Turbulence Modeling a Review for Different Used Methods

2021 ◽  
Vol 39 (1) ◽  
pp. 227-234
Author(s):  
Khelifa Hami
Keyword(s):  
Turbulence Modeling ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Simulation Models ◽  
Navier Stokes ◽  
Future Research ◽  
Detached Eddy Simulation ◽  
Navier Stokes Equations ◽  
Eddy Simulation ◽  
Complicated Geometries

This contribution represents a critical view of the advantages and limits of the set of mathematical models of the physical phenomena of turbulence. Turbulence models can be grouped into two categories, depending on how turbulent quantities are calculated: direct numerical simulations (DNS) and RANS (Reynolds Averaged Navier-Stokes Equations) models. The disadvantage of these models is that they require enormous computing power, inaccessible, especially for large and complicated geometries. For this reason, hybrid models (combinations between DNS and RANS methods) have been developed, for example, the LES (“Large Eddy Simulation”) or DES (“Detached Eddy Simulation”) models. They represent a compromise - are less precise than DNS, but more precise than RANS models. The results presented in this contribution will allow and facilitate future research in the field the choice of the model approach necessary for the case studies whatever their difficulty factor.

Large Eddy Simulation of Slurry Erosion in Submerged Impinging Jets

2020 ◽  
Author(s):  
Qiuchen Wang ◽  
Qiyu Huang ◽  
Xu Sun ◽  
Jun Zhang ◽  
Soroor Karimi ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Turbulence Models ◽  
Impinging Jets ◽  
Erosion Process ◽  
Slurry Erosion ◽  
Eddy Simulation ◽  
Erosion Prediction ◽  
Large Eddy

Abstract Submerged impingement jets are widely used in erosion/corrosion investigation as it is easy to control standoff distance as well as jet angle and flow velocities in experiments. In addition to experiments, typically Computational Fluid Dynamics (CFD) technique has been used to simulate slurry flow in this geometry to investigate erosion process and develop and verify erosion equations. This is done by solving Reynolds Averaged Navier-Stokes (RANS) equations with turbulence models, time-averaged fluid flow is revealed, and thus time-averaged erosion rate can be obtained by tracking particles in the fluid flow field. The current work shows that this seemingly simple flow displays unsteady flow structures in the stagnation zone of the flow field and its effects on erosion process was unclear. In this study, Large Eddy Simulation (LES) is used to simulate unsteady fluid flow in different impingement jets in Eulerian scheme. Then particles are injected randomly in the surface and tracked transiently to simulate unsteady erosion process in Lagrangian scheme. Finally, an erosion equation is used to calculate solid particle erosion rates. The LES Eulerian-Lagrangian erosion modeling are further validated by experimental fluid velocities and erosion profile measured before. It was found the accuracy of erosion prediction of small particles can be improved and unsteady properties can be well resolved by using this method.

Investigation of Analysis and Gradient-Based Design Optimization Using Neural Networks

2020 ◽  
Author(s):  
Kazuko W. Fuchi ◽  
Eric M. Wolf ◽  
David S. Makhija ◽  
Nathan A. Wukie ◽  
Christopher R. Schrock ◽  
...  
Keyword(s):  
Neural Networks ◽  
Design Optimization ◽  
Adaptive Systems ◽  
Automatic Differentiation ◽  
Transfer Problem ◽  
Approximate Solutions ◽  
Analysis And Design ◽  
Mesh Free Method ◽  
Gradient Based ◽  
Conventional Solution

Abstract Design optimization of adaptive systems requires a robust analysis method that can accommodate various changes in design and boundary conditions. In this work, physics-informed neural networks (PINNs) are used to approximate solutions to differential equations across a range of problem parameter values. This mesh-free method simply requires residual evaluation at sampling points within the analysis domain and along boundaries, and the training process does not require any reference problem to be solved through conventional solution methods. The trained model can be used to predict the solution field, conduct parameter space analysis and design optimization. Using automatic differentiation, the design objective and their derivatives can be computed as a post process for a gradient-based design optimization. The method is demonstrated in a 1D heat transfer problem governed by the steady-state heat equation. Use of the PINN model for design optimization is illustrated in a problem of finding a material transition location to minimize temperature at a specified location. The PINN model that does not include problem parameters as input can be trained to within 0.05% error. PINN models that involve problem parameters as inputs are more difficult to train, especially when the input-to-output relationship is complex.

Validation of Steady Average-Passage and Mixing Plane CFD Approaches for the Performance Prediction of a Modern Gas Turbine Multistage Axial Compressor

2008 ◽  
Author(s):  
Mahmoud L. Mansour ◽  
John Gunaraj ◽  
Shraman Goswami
Keyword(s):  
Flow Field ◽  
Turbulence Modeling ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Turbulence Models ◽  
Leading Edge ◽  
Sensitivity Study ◽  
Leakage Flow ◽  
Overall Performance

This paper summarizes the results of a validation and calibration study for two modern Computational Fluid Dynamics programs that are capable of modeling multistage axial compressors in a multi-blade row environment. The validation test case is a modern 4-stage high pressure ratio axial compressor designed and tested by Honeywell Aerospace in the late 90’s. The two CFD programs employ two different techniques for simulating the steady three-dimensional viscous flow field in a multistage/multiblade row turbo-machine. The first code, APNASA, was developed by NASA Glenn Research Center “GRC” and applies the approach by Adamczyk [1] for solving the average-passage equations which is a time and passage-averaged version of the Reynolds Averaged Navier Stokes (RANS) equations. The second CFD code is commercially marketed by ANSYS-CFX and applies a much simpler approach, known as the mixing-plane model, for combining the relative and the stationary frames of reference in a single steady 3D viscous simulation. Results from the two CFD programs are compared against the tested compressor’s overall performance data and against measured flow profiles at the leading edge of the fourth stator. The paper also presents a turbulence modeling sensitivity study aimed at documenting the sensitivity of the prediction of the flow field of such compressors to use of different turbulence closures such as the standard K-ε model, the Wilcox K-ω model and the Shear-Stress-Transport K-ω/SST turbulence model. The paper also presents results that demonstrate the CFD prediction sensitivity to modeling the compressor’s hub leakages from the inner-banded stator cavities. Comparison to the test data, using the K-ε turbulence closure, show that APNASA provides better accuracy in predicting the absolute levels of the performance characteristics. The presented results also show that better predictions by CFX can be obtained using the K-ω and the SST turbulence models. Modeling of the hub leakage flow was found to have significant and more than expected impact on the compressor predicted overall performance. The authors recommend further validation and evaluation for the modeling of the hub leakage flow to ensure realistic predictions for turbo-machinery performance.

scholarly journals Turbulence Modeling Effects on the CFD Predictions of Flow over a Detailed Full-Scale Sedan Vehicle

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 148 ◽  
Author(s):  
Chunhui Zhang ◽  
Charles Patrick Bounds ◽  
Lee Foster ◽  
Mesbah Uddin
Keyword(s):  
Turbulence Modeling ◽  
Computational Cost ◽  
Turbulence Models ◽  
Relative Magnitude ◽  
Full Scale ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Rans Turbulence Models ◽  
Rans Models

In today’s road vehicle design processes, Computational Fluid Dynamics (CFD) has emerged as one of the major investigative tools for aerodynamics analyses. The age-old CFD methodology based on the Reynolds Averaged Navier–Stokes (RANS) approach is still considered as the most popular turbulence modeling approach in automotive industries due to its acceptable accuracy and affordable computational cost for predicting flows involving complex geometries. This popular use of RANS still persists in spite of the well-known fact that, for automotive flows, RANS turbulence models often fail to characterize the associated flow-field properly. It is even true that more often, the RANS approach fails to predict correct integral aerodynamic quantities like lift, drag, or moment coefficients, and as such, they are used to assess the relative magnitude and direction of a trend. Moreover, even for such purposes, notable disagreements generally exist between results predicted by different RANS models. Thanks to fast advances in computer technology, increasing popularity has been seen in the use of the hybrid Detached Eddy Simulation (DES), which blends the RANS approach with Large Eddy Simulation (LES). The DES methodology demonstrated a high potential of being more accurate and informative than the RANS approaches. Whilst evaluations of RANS and DES models on various applications are abundant in the literature, such evaluations on full-car models are relatively fewer. In this study, four RANS models that are widely used in engineering applications, i.e., the realizable k - ε two-layer, Abe–Kondoh–Nagano (AKN) k - ε low-Reynolds, SST k - ω , and V2F are evaluated on a full-scale passenger vehicle with two different front-end configurations. In addition, both cases are run with two DES models to assess the differences between the flow predictions obtained using RANS and DES.

A Time-Resolved PIV Study of Vortical Structures in the Near-Wall Region of an Impinging Round Jet

2009 ◽  
Author(s):  
Khaled J. Hammad ◽  
Ivana M. Milanovic
Keyword(s):  
Flow Field ◽  
Turbulence Models ◽  
Wall Region ◽  
Vortex Identification ◽  
Time Resolved ◽  
Vortical Structures ◽  
Reynolds Decomposition ◽  
Gradient Based ◽  
Pod Analysis ◽  
Identification Techniques

Time-Resolved Particle Image Velocimetry (TR-PIV) was used to study the vortical structures resulting from a submerged water jet impinging normally on a smooth and flat surface. A fully developed turbulent jet, exiting a long pipe, and a semi-confined flow configuration ensured properly characterized boundary conditions, which allows for straightforward assessment of turbulence models and numerical schemes. The Reynolds number based on jet mean exit velocity was 23,000. The pipe-to-plate separation was varied between 2D and 7.6D. Turbulent velocity fields are presented using Reynolds decomposition into mean and fluctuating components. Proper Orthogonal Decomposition (POD) analysis was used to identify the most energetic coherent structures of the turbulent flow field. Three velocity gradient-based vortex identification techniques, 2nd invariant Q, λ2, and swirling strength, were found to perform equally well in identifying vortical structures along the impingement wall. The results clearly demonstrate the shortcomings of local vorticity as a vortex identifier in an impinging jet flow field.

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