scholarly journals Turbulence Modeling in the Age of Data

2019 ◽  
Vol 51 (1) ◽  
pp. 357-377 ◽  
Author(s):  
Karthik Duraisamy ◽  
Gianluca Iaccarino ◽  
Heng Xiao
Keyword(s):  
Turbulence Modeling ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Data Sets ◽  
Physical Constraints ◽  
The Past ◽  
Recent Developments ◽  
Rans Models ◽  
Engineering Models ◽  
Diverse Data

Data from experiments and direct simulations of turbulence have historically been used to calibrate simple engineering models such as those based on the Reynolds-averaged Navier–Stokes (RANS) equations. In the past few years, with the availability of large and diverse data sets, researchers have begun to explore methods to systematically inform turbulence models with data, with the goal of quantifying and reducing model uncertainties. This review surveys recent developments in bounding uncertainties in RANS models via physical constraints, in adopting statistical inference to characterize model coefficients and estimate discrepancy, and in using machine learning to improve turbulence models. Key principles, achievements, and challenges are discussed. A central perspective advocated in this review is that by exploiting foundational knowledge in turbulence modeling and physical constraints, researchers can use data-driven approaches to yield useful predictive models.

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.

scholarly journals ACAT1 Benchmark of RANS-Informed Analytical Methods for Fan Broadband Noise Prediction—Part I—Influence of the RANS Simulation

Acoustics ◽  
2020 ◽  
Vol 2 (3) ◽  
pp. 539-578
Author(s):  
Carolin Kissner ◽  
Sébastien Guérin ◽  
Pascal Seeler ◽  
Mattias Billson ◽  
Paruchuri Chaitanya ◽  
...  
Keyword(s):  
Turbulence Model ◽  
Analytical Methods ◽  
Companion Paper ◽  
Broadband Noise ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Data Set ◽  
The Past ◽  
Flow Turbulence ◽  
Diverse Data

A benchmark of Reynolds-Averaged Navier-Stokes (RANS)-informed analytical methods, which are attractive for predicting fan broadband noise, was conducted within the framework of the European project TurboNoiseBB. This paper discusses the first part of the benchmark, which investigates the influence of the RANS inputs. Its companion paper focuses on the influence of the applied acoustic models on predicted fan broadband noise levels. While similar benchmarking activities were conducted in the past, this benchmark is unique due to its large and diverse data set involving members from more than ten institutions. In this work, the authors analyze RANS solutions performed at approach conditions for the ACAT1 fan. The RANS solutions were obtained using different CFD codes, mesh resolutions, and computational settings. The flow, turbulence, and resulting fan broadband noise predictions are analyzed to pinpoint critical influencing parameters related to the RANS inputs. Experimental data are used for comparison. It is shown that when turbomachinery experts perform RANS simulations using the same geometry and the same operating conditions, the most crucial choices in terms of predicted fan broadband noise are the type of turbulence model and applied turbulence model extensions. Chosen mesh resolutions, CFD solvers, and other computational settings are less critical.

Numerical Investigation of the Flow in a Coaxial Piping System

2014 ◽  
Author(s):  
Charles Farbos de Luzan ◽  
Yuri Perelstein ◽  
Ephraim Gutmark ◽  
Thomas Frosell ◽  
Frederic Felten
Keyword(s):  
Flow Field ◽  
Turbulence Models ◽  
Field Measurements ◽  
Industrial Applications ◽  
Navier Stokes ◽  
Piping System ◽  
Image Velocimetry ◽  
Rans Models ◽  
Recirculation Zones ◽  
The One

A coaxial piping system (CPS) that involves a transition from a smaller annulus into a larger annulus is investigated to evaluate the generation of vortices and recirculation zones around the transition area. These areas are of interest for industrial applications where erosion within the piping system is a concern. The focus of this work is to evaluate the capabilities of Computational Fluid Dynamics (CFD) using commercial Reynolds-Averaged Navier Stokes (RANS) models to predict the regions and intensity of vortices and recirculation zones. A trusted grid is developed and used to compare turbulence models. The commercial CFD solver Fluent (Ansys Inc., USA) is used to solve the flow governing equations for different CFD numerical formulations, namely the one equation Spalart-Allmaras model, and steady-state RANS with different turbulence models (standard k-epsilon, k-epsilon realizable, k-epsilon RNG, standard k-omega, k-omega SST, and transition SST) [1]. CFD results are compared to time-averaged particle image velocimetry (PIV) measurements. The PIV provides 3D flow field measurements in the outer annulus of the piping system. Velocities in regions of interest were used to compare each model to the PIV results. An RMS comparison of the numerical results to the measured values is used as a quantitative evaluation of each turbulence model being considered. The results provide a useable CFD model for evaluation of the flow field of this flow field and highlights areas of uncertainty in the CFD results.

scholarly journals Numerical and Experimental Investigation of the Wake Flow Downstream of a Linear Turbine Cascade

1998 ◽  
Author(s):  
Wolfgang Sanz ◽  
Arno Gehrer ◽  
Jakob Woisetschläger ◽  
Martin Forstner ◽  
Wolfgang Artner ◽  
...  
Keyword(s):  
Turbulence Modeling ◽  
Turbulence Models ◽  
Wake Flow ◽  
Navier Stokes ◽  
Laser Doppler Velocimeter ◽  
Turbine Cascade ◽  
Trailing Edge ◽  
Blunt Trailing Edge ◽  
And Performance ◽  
Transonic Cascade

In turbomachinery the wake flow together with the inherent unsteadiness caused by interaction between stator and rotor has a significant impact on efficiency and performance. The prediction of the wake flow depends largely on the turbulence modeling. Therefore in this study the evolution of a viscous wake downstream of a linear turbine cascade is experimentally and computationally investigated. In a transonic cascade test stand Laser Doppler Velocimeter (LDV) measurements of velocity and turbulent kinetic energy are done in several axial planes downstream of the blade trailing edge. Two different turbulence models are then incorporated into a two-dimensional Navier-Stokes solver to calculate the turbulent wake flow and the results are compared with the experimental data to test the quality of the turbulence models. The large discrepancies between measurement and Calculation are assumed to be caused by the periodic vortex shedding from the blunt trailing edge which is not taken into account by the turbulence models. But further research is needed to resolve this issue.

Investigation of the Accuracy of RANS Models to Predict the Flow Through a Low-Pressure Turbine

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
R. Pichler ◽  
R. D. Sandberg ◽  
V. Michelassi ◽  
R. Bhaskaran
Keyword(s):  
Linear Models ◽  
Turbulence Modeling ◽  
A Priori ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Low Pressure ◽  
Transport Equations ◽  
Compressible Turbulence ◽  
Low Pressure Turbine ◽  
Rans Models

In the present paper, direct numerical simulation (DNS) data of a low-pressure turbine (LPT) are investigated in light of turbulence modeling. Many compressible turbulence models use Favre-averaged transport equations of the conservative variables and turbulent kinetic energy (TKE) along with other modeling equations. First, a general discussion on the turbulence modeling error propagation prescribed by transport equations is presented, leading to the terms that are considered to be of interest for turbulence model improvement. In order to give turbulence modelers means of validating their models, the terms appearing in the Favre-averaged momentum equations are presented along pitchwise profiles at three axial positions. These three positions have been chosen such that they represent regions with different flow characteristics. General trends indicate that terms related with thermodynamic fluctuations and Favre fluctuations are small and can be neglected for most of the flow field. The largest errors arise close to the trailing edge (TE) region where vortex shedding occurs. Finally, linear models and the scope for their improvement are discussed in terms of a priori testing. Using locally optimized turbulence viscosities, the improvement potential of widely used models is shown. On the other hand, this study also highlights the danger of pure local optimization.

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.

scholarly journals A curated dataset for data-driven turbulence modelling

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Ryley McConkey ◽  
Eugene Yee ◽  
Fue-Sang Lien
Keyword(s):  
Machine Learning ◽  
Turbulence Models ◽  
Turbulence Modelling ◽  
Navier Stokes ◽  
Square Duct ◽  
Eddy Simulation ◽  
Initial Dataset ◽  
Diverging Channel ◽  
Rans Models ◽  
New Feature

AbstractThe recent surge in machine learning augmented turbulence modelling is a promising approach for addressing the limitations of Reynolds-averaged Navier-Stokes (RANS) models. This work presents the development of the first open-source dataset, curated and structured for immediate use in machine learning augmented corrective turbulence closure modelling. The dataset features a variety of RANS simulations with matching direct numerical simulation (DNS) and large-eddy simulation (LES) data. Four turbulence models are selected to form the initial dataset: k-ε, k-ε-ϕt-f, k-ω, and k-ω SST. The dataset consists of 29 cases per turbulence model, for several parametrically sweeping reference DNS/LES cases: periodic hills, square duct, parametric bumps, converging-diverging channel, and a curved backward-facing step. At each of the 895,640 points, various RANS features with DNS/LES labels are available. The feature set includes quantities used in current state-of-the-art models, and additional fields which enable the generation of new feature sets. The dataset reduces effort required to train, test, and benchmark new corrective RANS models. The dataset is available at 10.34740/kaggle/dsv/2637500.

Synthesis of a CFD Benchmark for the Thermal Mixing in a Sharp Corner T-Junction With a Wall

2018 ◽  
Author(s):  
Afaque Shams ◽  
Nicolas Edh ◽  
Kristian Angele
Keyword(s):  
Thermal Field ◽  
Turbulence Models ◽  
Temperature Fluctuations ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Sharp Corner ◽  
Cfd Validation ◽  
Thermal Mixing ◽  
Eddy Simulation ◽  
Rans Models

This article reports a CFD-benchmark with the purpose of validating different turbulence modelling approaches for the transient heat transfer due to mixing of hot and cold flow in a T-junction including the wall. This validation exercise has been carried out within the MOTHER project. In the framework of the project, new experiments were performed with a novel measurement sensor allowing the measurements of the fluctuating wall temperature inside the solid pipe wall. The tests were performed for two different Reynolds numbers (Re) 40000 and 60000 and for two different T-junction geometries; a sharp corner and a round corner. The present article reports the synthesis of the CFD validation for a sharp corner T-junction for Re = 40 000. The CFD validation study has been performed using four different CFD softwares, namely STAR-CCM+, Code_Saturne, LESOCC2 and Fluent. In addition, five different turbulence models i.e. wall-function Large Eddy Simulation (LES), Deatched Eddy Simulation (DES), Partially Resolved Numerical Simulation (PRNS), Unsteady Reynolds Averaged Navier-Stokes URANS and RANS were used to perform the CFD computations. The validation exercise has shown that LES gives the best agreement with the experimental data followed by hybrid (LES/RANS), URANS and RANS models, respectively. The velocity and the thermal fields in the fluid region are correctly predicted by the proper use of the LES modelling, whereas, the accurate prediction of the thermal field in the solid requires very long sampling time in order to achieve a statistically converged solution, which of course requires an enormous computational power. Therefore, the statistical convergence of the thermal field in the solid has been found to be a bottleneck in order to accurately predict the temperature fluctuations in the wall. However, measuring the small amplitude temperature fluctuations is also associated with an uncertainty so the disagreement between CFD and measurements (of the order of 10 %) can also be attributed, in part, to uncertainties in the measurements.

scholarly journals COMPARISON OF NUMERICAL WAVE TANKS WITH VARIOUS TURBULENCE MODELS IN APPLICATION TO LONG WAVE MOTION AND ITS INTERACTION WITH A VERTICAL WALL

2018 ◽  
pp. 29
Author(s):  
Gizem Ezgi Cinar ◽  
Hasan Gokhan Guler ◽  
Taro Arikawa ◽  
Cuneyt Baykal ◽  
Ahmet Cevdet Yalciner
Keyword(s):  
Wave Motion ◽  
Turbulence Modeling ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Computational Time ◽  
Long Wave ◽  
Large Eddy ◽  
Numerical Wave

In this study, performances of interFoam solver of OpenFOAM and CADMAS-SURF computational tools with several turbulence modelling approaches on the numerical modelling of long wave motion and its interaction with a vertical wall based on the physical model experiments presented by Arikawa (2015) are investigated and compared. IHFOAM is used as wave generation and absorption boundary condition (Higuera et al., 2013). Three-dimensional simulations are carried out solving Reynolds Averaged Navier Stokes (RANS) with no-turbulence model and with k-ε and k-ω SST (Shear Stress Transport) turbulence models in addition to Large Eddy Simulations (LES). The aim of this study is to understand the contribution from turbulence modeling and compare the numerical wave tanks in long wave motion and their interaction with a vertical wall. The results are further discussed in scope of required accuracy in such engineering applications focusing on computational time.

A Methodology for Simulating Compressible Turbulent Flows

2005 ◽  
Vol 73 (3) ◽  
pp. 405-412 ◽  
Author(s):  
Hermann F. Fasel ◽  
Dominic A. von Terzi ◽  
Richard D. Sandberg
Keyword(s):  
Turbulent Flows ◽  
Compressible Flows ◽  
Bluff Body ◽  
Turbulence Modeling ◽  
Flow Behavior ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Fine Grid ◽  
Local Flow

A flow simulation Methodology (FSM) is presented for computing the time-dependent behavior of complex compressible turbulent flows. The development of FSM was initiated in close collaboration with C. Speziale (then at Boston University). The objective of FSM is to provide the proper amount of turbulence modeling for the unresolved scales while directly computing the largest scales. The strategy is implemented by using state-of-the-art turbulence models (as developed for Reynolds averaged Navier-Stokes (RANS)) and scaling of the model terms with a “contribution function.” The contribution function is dependent on the local and instantaneous “physical” resolution in the computation. This physical resolution is determined during the actual simulation by comparing the size of the smallest relevant scales to the local grid size used in the computation. The contribution function is designed such that it provides no modeling if the computation is locally well resolved so that it approaches direct numerical simulations (DNS) in the fine-grid limit and such that it provides modeling of all scales in the coarse-grid limit and thus approaches a RANS calculation. In between these resolution limits, the contribution function adjusts the necessary modeling for the unresolved scales while the larger (resolved) scales are computed as in large eddy simulation (LES). However, FSM is distinctly different from LES in that it allows for a consistent transition between RANS, LES, and DNS within the same simulation depending on the local flow behavior and “physical” resolution. As a consequence, FSM should require considerably fewer grid points for a given calculation than would be necessary for a LES. This conjecture is substantiated by employing FSM to calculate the flow over a backward-facing step and a plane wake behind a bluff body, both at low Mach number, and supersonic axisymmetric wakes. These examples were chosen such that they expose, on the one hand, the inherent difficulties of simulating (physically) complex flows, and, on the other hand, demonstrate the potential of the FSM approach for simulations of turbulent compressible flows for complex geometries.

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