Performance Of Turbulence Models Research Articles

Continuous Eddy Simulation (CES) of Transonic Shock-Induced Flow Separation

Reynolds-averaged Navier–Stokes (RANS), large eddy simulation (LES), and hybrid RANS-LES, first of all wall-modeled LES (WMLES) and detached eddy simulation (DES) methods, are regularly applied for wall-bounded turbulent flow simulations. Their characteristic advantages and disadvantages are well known: significant challenges arise from simulation performance, computational cost, and functionality issues. This paper describes the application of a new simulation approach: continuous eddy simulation (CES). CES is based on exact mathematics, and it is a minimal error method. Its functionality is different from currently applied simulation concepts. Knowledge of the actual amount of flow resolution enables the model to properly adjust to simulations by increasing or decreasing its contribution. The flow considered is a high Reynolds number complex flow, the Bachalo–Johnson axisymmetric transonic bump flow, which is often applied to evaluate the performance of turbulence models. A thorough analysis of simulation performance, computational cost, and functionality features of the CES model applied is presented in comparison with corresponding features of RANS, DES, WMLES, and wall-resolved LES (WRLES). We conclude that CES performs better than RANS, DES, WMLES, and even WRLES at a little fraction of computational cost applied for the latter methods. CES is independent of usual functionality requirements of other methods, which offers relevant additional advantages.

Comparison of RANS and LES turbulent flow models in a real stenosis

This study focuses on the performance of various turbulence models in predicting hemodynamic variables within a patient-specific geometry of the Brachiocephalic trunk exhibiting a severe stenosis. Numerical simulations employing Reynolds-averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) models were conducted, comparing four RANS with two LES models. Results indicated significant differences in turbulent structures between RANS and LES models, with the k-ω RANS model closely approximating LES throughout the cardiac cycle. The velocity and Turbulent Kinetic Energy (TKE) results were consistent in the stenosis region due to the proximity to the inlet and plug flow conditions. However, notable disparities were observed in bifurcation and outlet regions. Time-Averaged Wall Shear Stress (TAWSS) comparisons revealed that the k-ω-based models provided closer agreement with LES, particularly in atherosclerosis-prone areas. The study highlights the limitations and strengths of each turbulence model, emphasizing the importance of model selection in simulating complex cardiovascular conditions. While RANS models demonstrated computational efficiency, their accuracy varied across regions. The effectiveness of the k-ω model in capturing the intricacies of such a complex flow field suggests its potential as a reliable and accurate tool for simulating physiological conditions with strong curvature and advanced stenosis.

Comparison of Eddy Viscosity Models for High Turbulence Nozzle Guide Vane Flows

Abstract In this paper we investigate the performance of eddy viscosity turbulence models for high-pressure nozzle guide vane (NGV) flows with engine-realistic turbulence. Using metrics such as integrated kinetic energy (KE) loss and mixing rate, we compare simulation results using turbulence models with high-fidelity experimental data from fully-cooled NGVs, operating at engine-matched conditions of Reynolds number and Mach. For the widely-used k–ω shear stress transport (SST) model, the aerodynamic and thermal wakes of the NGVs were undermixed. We compare simulation results with those using other common turbulence models including the standard k–ω, baseline k–ω, Spalart–Allmaras, and baseline explicit algebraic Reynolds stress model. Alternative turbulence models formulations are explored, with an emphasis on modifications to the implementation of the shear stress limiter. We also investigate the sensitivity of models to the specified inlet turbulence intensity. We demonstrate that predictions of integrated KE loss, as well as the decay trends of the aerodynamic and thermal wakes are a closer match to experimental data for the baseline algebraic Reynolds stress model than for other turbulence models in more common use for NGV predictions.

Turbulence models performance to predict fluid mechanics and heat transfer characteristics of fluids flow in micro-scale channels

The predictability of the mathematical models on the details and the phenomenology for microscale flow conditions is an open topic in the literature. In this sense, this work evaluates the capacity of the following turbulence models: standard k − ε , RNG k − ε , k − ω standard, k − ω SST , Realizable k − ε , and Low-Re k − ε to predict the fluid mechanics and heat transfer characteristics of low Global Warming Potential (GWP) fluid flow in a 1.1 mm ID microchannel. These turbulence models are evaluated for Reynolds Numbers up to 104. The numerical results for velocity profile, friction factors, and Nusselt Numbers are validated with analytical and experimental data published in previous works for R134a, R1234yf, R1234ze(E), and R600a. Parametric behaviors of pressure drop and heat transfer coefficient are presented and analyzed. The results indicate that each of the models describes the qualitative behavior of flow and heat transfer processes. On the other hand, the quantitative results indicate that the Low-Re k − ε , k − ω , and k − ω SST models demonstrate an acceptable prediction of some variable’s behavior. Numerically, the Low-Re k − ε model presents an accurate prediction with the lowest mean absolute.

Experimental and numerical study on flow field characteristics of a combustion chamber with double-stage counter-rotating swirlers

To discover a good predictive turbulent model and reveal the mechanism of turbulent mixing enhancement, a new combustion chamber equipped with a double-stage counter-rotating swirler with vane angles of both stages as 45° is proposed and the flow field characteristics are explored by combining 2D-PIV experiment and Reynolds averaged numerical simulation (RANS). Firstly, the performance of various turbulence models in predicting the flow field characteristics is evaluated by comparing them with experimental results. The study concludes that the RNG k-ε turbulence model exhibits superior performance in predicting velocity distribution, recirculation zone length, and vorticity distribution. Hence, it is selected to analyze the influence of the Reynolds number (Re) of swirlers on the flow field characteristics. In this study, seven Re numbers ranged from 5425 to 54,245 were selected for analysis. Through comparison, it appears that changes in Re number have a strengthening effect on the flow field at various locations, including the recirculation zone, wall surface, and shear layer. This suggests that Re number has an influence on turbulence or boundary layer behavior. Interestingly, there seems to be a critical value for Re number of 21,698, which may be related to a competition between Re number and wall effects.

Numerical Simulation of Supersonic Turbulent Separated Flows Based on k–ω Turbulence Models with Different Compressibility Corrections

The accurate prediction of supersonic turbulent separated flows involved in aerospace vehicles is a great challenge for current numerical simulations. Based on the k–ω equations, several different compressibility corrections are incorporated in turbulence models to improve their prediction capabilities. Two benchmark test cases, namely the ramped cavity and the compression corner, are adopted for the numerical validation. Detailed comparisons between simulations and experiments are conducted to evaluate the effect of compressibility corrections on turbulence models. The computed results indicate that compressibility corrections have a significant impact on turbulence model performance. The compressibility correction, considering the effects of both dilatation dissipation and pressure dilatation, is suitable for the prediction of compressible free shear layers, but it may have a negative impact on the prediction of low-speed flows in the near-wall region due to the severe underprediction of the wall skin friction coefficient. In comparison, the compressibility correction only considering the effects of dilatation dissipation is conservative, with decreased predictability of free shear layers in supersonic flows, although it improves the predictions of the original models without corrections.

CFD simulation of pollutant dispersion using anisotropic models: Application to an urban like environment under neutral and stable atmospheric conditions

Modeling the atmospheric dispersion of pollutants emitted from different types of sources under various atmospheric conditions is an essential prerequisite for risk assessment studies and emergency preparedness. In this study, we evaluate the performance of different turbulence models and velocity-scalar correlation models implemented in the Code_Saturne. The evaluation is done with observations of four trial cases of the Mock Urban Setting Test (MUST) campaign in an urban type environment and in neutral and stable atmospheric conditions. For all of the trials studied, the CFD model with a first-order closure model (k−ɛ) predicts 61.1% of the concentrations within a factor of two of the observations, which is higher than the percentage of predicted points (58.8%) when a second-order closure model (Rij−ɛ) is used. Overall, the CFD model underestimates observed concentrations, regardless of the turbulence model used. For the trial with slightly stable conditions, the results show that the k−ɛ model combined with an algebraic SGDH model predicts 75% concentrations within a factor of two of the observations. The performance of the k−ɛ model is compared to that of the Rij−ɛ model when used with the algebraic SGDH, GGDH models and with the scalar flux transport equation (DFM model). Under slightly stable atmospheric conditions, the DFM model predicts 69% of concentrations within a factor of two of observations, showing promise for modeling under these conditions, despite its relatively high computational cost.

Comparison of various turbulence models in wind tunnels

Wind tunnel test is widely used in aviation, automobile, construction and other fields to simulate the force and flow field distribution of objects in the wind field. However, due to the existence of complex flow phenomena such as turbulence, the accuracy of the wind tunnel test is affected to a certain extent. Therefore, it is of great significance to study the performance of various turbulence models in the wind tunnel to improve the accuracy of the wind tunnel test. This study compares and analyzes the performance of turbulence models in wind tunnel experiments. Based on various turbulence models, numerical simulation methods are employed to simulate and calculate the flow field in wind tunnel experiments, and the results are compared. Through the comparison and analysis, it is found that different turbulence models exhibit different performance in simulating wind tunnel experiments. Among them, the RSM model demonstrates better accuracy and stability, without the presence of boundary layer effects. The purpose of this research is to evaluate and analyze the applicability of various turbulence models in wind tunnel experiments, provide references and guidance for flow field simulations in wind tunnel testing. However, limitations of this study lie in the constraints of the models and computational methods used, and further research and exploration are needed to address these limitations.

Economic particulate transport performance analysis of k-epsilon models in highly concentrated slurry through pipelines

The paper analyzed the economic transporting performance of k-epsilon turbulence models using the Eulerian two-fluid approach in transporting highly concentrated fine particulate slurry through horizontal pipelines using Kaushal et al. (2005) experimental data of glass beads slurry of 125 μm mean diameter for volumetric concentration ranging 30%–52% and flow velocity ranging 2–5 m/s. The primary components of economical slurry transport are Specific Energy consumption (SEC) and pressure drop; both have been examined in the performance of different κ-ϵ models and are yet to be unlighted on these parameters. The CFD model found the excellent performance of all k-epsilon models with slightly more effectiveness in the case of the Realizable κ-ϵ model. The analyzed and validated CFD model was subsequently used in examining the parameters of slurry flow, such as the secondary phase velocity, concentration distribution, and SEC analysis for the range of fine particles 125, 150, and 212 µm. The plotted contours from CFD are useful in visualizing slurry flow parameters at intermediates inlet values for slurry inlet flow velocity ranging 2–6 m/s and inlet volumetric concentration ranging 30%–55% for fine particles. Analysis revealed that the highly concentrated fine particles slurry transported at optimum volumetric concentration range of 40–45% are economical slurry transport.

Progressive augmentation of Reynolds stress tensor models for secondary flow prediction by computational fluid dynamics driven surrogate optimisation

Generalisability and the consistency of the a posteriori results are the most critical points of view regarding data-driven turbulence models. This study presents a progressive improvement of turbulence models using simulation-driven Bayesian optimisation with Kriging surrogates where the optimisation of the models is achieved by a multi-objective approach based on duct flow quantities. We aim for the augmentation of secondary-flow prediction capability in the linear eddy-viscosity model k−ω SST without violating its original performance on canonical cases e.g. channel flow. Progressively data-augmented explicit algebraic Reynolds stress models (PDA-EARSMs) for k−ω SST are obtained enabling the prediction of secondary flows that the standard model fails to predict. The new models are tested on channel flow cases guaranteeing that they preserve the successful performance of the original k−ω SST model. Subsequently, numerical verification is performed for various test cases. Regarding the generalisability of the new models, results of unseen test cases demonstrate a significant improvement in the prediction of secondary flows and streamwise velocity. These results highlight the potential of the progressive approach to enhance the performance of data-driven turbulence models for fluid flow simulation while preserving the robustness and stability of the solver.

Assessment of advanced RANS models to predict the heat transfer for supercritical fluids in vertical tubes

The extreme thermophysical property changes of fluids near the pseudocritical point lead to strong buoyancy and acceleration effects, posing challenges for turbulence modelling. This paper aims to assess the performance and applicability of various turbulence models, with the intention of providing a useful reference for quickly selecting appropriate models and for models’ further improvement. Additional Favre-averaged turbulence models were implemented through user-defined scalars in ANSYS Fluent and compared to published experimental and high-fidelity simulation data. This study found that the tested turbulence models have different sensitivities to molecular Prandtl numbers, buoyancy effects, and flow acceleration. For forced convection, all turbulence models can be applied in the case of the flow acceleration number Kv<1.37×10−8, and the ZXY model has the widest application range. None of the tested turbulence models showed generalizability under mixed convective conditions. The Lien-PSA model qualitatively reproduced the wall temperature trends for all tested cases.

On the Measure of the Heat Transfer Performance of RANS Turbulence Models in Single Round Jet Impingement

The jet impingement phenomenon is one of the processes which can enhance heat transfer. Due to its complex nature, it has been the subject of many experimental and numerical analyses in which researchers have tried to quantify and qualitatively describe it. However, the lack of crucial information regarding procedures, accuracy, geometry settings, boundary conditions, etc. makes it challenging to compare the results, validate turbulence models, and reproduce data. In this publication, the authors show a consistent and systematic numerical analysis of round and turbulent jet impingement based on RANS turbulence models. The results have been calculated for various geometrical configurations, Reynolds number values, and turbulence models, and compared with experimental and numerical data available in the literature to show their similarities and differences. It led to unique data collection, which was used in the novel quantitative analysis and helped lead to proposing the measure of the heat transfer performance of a particular turbulence model. Such a measure has not been reported so far. The measure exhibited that no turbulence model is suitable for all analyzed parameters. Quantitative comparisons enable recommendations of turbulence models for analyzed cases which have the potential to accelerate the design process of devices and could be a source of suggestions for other researchers.

Turbulence Model Effects on Vortex Interaction Prediction on a Multiswept Delta Wing

In this study, vortical flows around a generic triple-delta wing geometry were investigated at transonic speeds. The focus of this work was the investigation of vortex interaction at medium to high angles of attack. To this end, numerical simulations were performed at two different Mach numbers, M=0.5 and M=0.85. To assess the performance of different turbulence models in predicting the complex flowfield, comparisons with experimental data were performed. In addition to the integral forces and moments, surface pressures from pressure-sensitive paint and velocity field data from particle image velocimetry were used. Across all investigated test cases, the best agreement with experimental results was achieved by the Menter shear stress transport turbulence model.

Evaluation of dynamic correction of turbulence wall boundary conditions to simulate roughness effect in minichannel with rotating walls

PurposeThe purpose of this study is an assessment of the existing roughness models to simulate the flow in the narrow gap between corotating and rough disks. A specific configuration of the flow through the gap, which forms a minichannel with variable cross sections and rotating walls, makes it a complex problem and, therefore, worth discussing in more detail.Design/methodology/approachTwo roughness models were examined, the first one was based on the wall function modification by application of the shift in the dimensionless velocity profile, and the second one was based on the correction of turbulence parameters at the wall, proposed by Aupoix. Due to the lack of data to validate that specific case, the approach to deal with was selected after a systematic study of reported test cases. It started with a zero-pressure-gradient boundary layer in the flow over a flat plate, continued with flow through minichannels with stationary walls, and finally, focused on the flow between corotating discs, pertaining each time to smooth and rough surfaces.FindingsThe limitations of the roughness models were highlighted, which make the models not reliable in the application to minichannel flows. It concerns turbulence models, near-wall discretization and roughness approaches. Aupoix’s method to account for roughness was selected, and the influence of minichannel height, mass flow rate, fluid properties and roughness height on the velocity profile between corotating discs in both smooth and rough cases was discussed.Originality/valueThe originality of this study is the evaluation and validation of different methods to account for the roughness in rotating mini channels, where the protrusions can cover a substantial part of the channel. Flow behavior and performance of different turbulence models were analyzed as well.

CFD modelling of initial stages of dam-break flow

Cases of dam failures are seen almost every year globally, and the propagation of rapidly varying unsteady flows resulting from those dam failures has significant environmental and economic consequences. A three-dimensional Computational Fluid Dynamics model was created to solve unsteady Reynolds-Averaged equations to investigate the generation and propagation of dam-break flows and reflected flood waves in the presence of a trapezoidal bottom obstacle. The dam-breaks were modelled using OpenFOAM based on the Volume of Fluid method employing the Finite Volume Method, and the performance of various Reynolds-Averaged Navier-Stokes turbulence models, including the realizable k − ε, SST k − ω (Shear Stress Transport k − ω), and v2 − f models, has been evaluated. To assess the capabilities of the different turbulence models, quantitative comparisons of numerical simulations with laboratory experiments were completed, and it was found that the SST k − ω model performed better in predicting the free surface profiles and negative bore propagation speeds than the realizable k − ε and v2 − f models.

Mesh-Free Analysis of a Vertical Axis Wind Turbine Using Lattice Boltzmann Method and Various Turbulence Models

This study aims to investigate the aerodynamic analysis of a Darrieus-type vertical axis wind turbine (VAWT) using the Lattice Boltzmann Method (LBM). The objective is to assess the accuracy and performance of the meshless LBM approach in predicting torque coefficients, velocity, turbulence intensity, and vorticity distributions for VAWT aerodynamic analysis. Two turbulence modelling approaches, Large Eddy Simulation (LES) and Reynolds-Averaged Navier-Stokes (RANS), are employed to model the flow domain. The central problem revolves around comparing the performance of different turbulence models based on their agreement with experimental results for power and torque coefficients. The findings demonstrate the effectiveness of the WALE turbulence model in achieving the best agreement with experimental data. Overall, the study provides valuable insights into applying LBM in VAWT aerodynamic analysis and highlights the advantages of the meshless approach compared to traditional CFD methods.

CFD simulations of the refueling of long horizontal H2 tanks with tilted injector

With the recent development of Hydrogen Refueling Stations (HRS), the refueling of hydrogen composite tanks is an important issue for the safe handling of hydrogen. In particular, an appropriate protocol is needed to avoid tank overheating during refueling. To model the temperature distribution everywhere inside the tank during these processes, CFD (Computational Fluid Dynamics) simulations have been performed under cases where thermal stratification occurs. The performances of several CFD turbulence models are benchmarked through a comparison with experimental data. Two injector configurations are considered in this work: a straight one and another tilted upwards. The U-RANS (Unsteady-Reynolds Averaged Navier-Stokes) - Reynolds Stress Model (RSM) is found to be the most reliable turbulence model for both configurations.

Assessment of Engineering Turbulence Models in Buoyant Diabatic Turbulent Flow

Turbulent heat transfer in buoyancy-dominated flows is a challenging problem for computational fluid dynamics (CFD). Many authors attribute model error in these conditions to the Reynolds analogy. We leverage a brand-new direct numerical simulation database to evaluate the performance of several popular turbulence models in buoyant diabatic channel flow. We find that heat transfer results are relatively accurate, with a Nusselt number error less than 20%. However, the turbulent flow solution is very inaccurate, with wall shear overpredicted by up to 100%. This indicates significant turbulence model error in such flows. We determined that the dominant sources of model error are missing physics in the algebraic Reynolds stress framework and the simple buoyancy production term used in industrial CFD. We suggest that future modeling efforts focus on these two sources of model error. We demonstrate that the Reynolds analogy is not the dominant source of model error.

Numerical simulation of scour at the rear side of a coastal revetment

This paper presents the results of a numerical modeling study on the scouring of unprotected rear side material of a rubble mound coastal revetment due to the overtopping of solitary-like waves utilizing a coupled hydro-morphodynamic computational fluid dynamics (CFD) model. Three cases having various wave heights are tested with six different turbulence models together with different wall functions. The hydrodynamic results (free-surface elevations, overtopping volumes, and jet thicknesses) and morphological results (scour profile and scour hole properties) are compared with the existing experimental data to evaluate the performances of different turbulence models and wall functions. It is found that the numerical model can predict the hydrodynamic and morphological results with a high level of accuracy when the appropriate turbulence model and wall function are used. The importance of turbulence in the scouring processes and the turbulence modeling approach in hydro-morphodynamic CFD simulations are highlighted.

RANS thermal modelling of a natural convection boundary layer at low Prandtl number

The present work evaluates the performance of different RANS turbulence models in a natural convection boundary layer at three different Prandtl numbers: 0.71, 0.2 and 0.025. An assessment on the prediction of the boundary layer is presented in function of the wall fluxes, mean and turbulent flow fields. It is observed that the chosen turbulence model to close the momentum equation is relevant in order to capture the flow field at low Prandtl numbers. This is due to the strong interaction between the momentum and thermal fields in natural convection. From the thermal point of view, the analogy between the turbulent momentum and turbulent thermal diffusivities presents serious issues to correctly predict the flow field independently of the Prandtl number. Advanced models that employ algebraic or transport equations of the turbulent heat fluxes introduces the needed physics to correctly predict the natural convection boundary layer.