We introduce a novel approach to derive compressibility corrections for Reynolds-averaged Navier-Stokes (RANS) models. Using this approach, we derive variable-property corrections for wall-bounded flows that take into account the distinct scaling characteristics of the inner and outer layers, extending the earlier work of Otero Rodriguez et al. [Int. J. Heat Fluid Flow, 73, 2018]. We also propose modifying the eddy viscosity to account for changes in the near-wall damping of turbulence due to intrinsic compressibility effects. The resulting corrections are consistent with our recently proposed velocity transformation [Hasan et al., Phys. Rev. Fluids, 8, L112601, 2023] in the inner layer and the Van Driest velocity transformation in the outer layer. Furthermore, we address some important aspects related to the modeling of the energy equation, primarily focusing on the turbulent Prandtl number and the modeling of the source terms. Compared to the existing state-of-the-art compressibility corrections, the present corrections, combined with accurate modeling of the energy equation, lead to a significant improvement in the results for a wide range of turbulent boundary layers and channel flows. The proposed corrections have the potential to enhance modeling across a range of applications, involving low-speed flows with strong heat transfer, fluids at supercritical pressures, and supersonic and hypersonic flows.

This paper describes a recently developed two-equation Reynolds-averaged Navier–Stokes (RANS) turbulence model called Generalized [Formula: see text] (GEKO). The model is formulated to include tunable coefficients that can be utilized to adjust the model’s behavior to specific application cases. Contrary to existing models, where model coefficients are inter-related and tightly connected to basic validation cases, the newly introduced coefficients are independent from one another and can be adjusted within given ranges without negative effects on the essential model calibration for wall-bounded flows.

The article investigates the feasibility of Large Eddy Simulation methods to accurately compute the flow around the Ahmed car body at 25^∘ slant angle. The flow is computed at two different Reynolds numbers and with different turbulence modeling concepts using a large variety of grids. Issues associated with the accurate computation of the separation at the slant onset will be discussed in detail.

For swirl-stabilized gas turbine combustors, turbulence modelling is generally undertaken using Scale-Resolved Simulations (SRS) methods such as Large Eddy Simulations (LES). However, LES is expensive due to large mesh sizes and small time-step size required to estimate the correct large-scale turbulence motion generated within the combustor domain. While Reynolds Averaged Navier Stokes (RANS) models are computationally very efficient in predicting qualitative behaviour, such models lack fidelity to predict complex flow characteristics such as swirl accurately. In previous studies with commercial Computational Fluid Dynamics (CFD) code, the Generalized k-omega (GEKO) based RANS model has been used for simulation of turbulent flows. The free-coefficients of the GEKO model are tuned to predict the characteristics of potential flow undergoing separation. In this paper, LES predictions are used as baseline results which are used to generate a sensitivity field by using an Adjoint solver. Machine learning (ML) via Neural Network (NN) Training is utilized to create a correlation between suitable turbulent flow features and optimal GEKO parameters, aiding the trained model’s generalization. This allows computationally faster simulations of swirling flow with optimized GEKO model compared to LES. In this paper, an industrial configuration named as the DLR PRECCINSTA burner has been used considering a cold non-reacting flow. The computations are performed with LES, and the results match the experiments for directional velocities at different sections within the combustor. The LES solution is used to train the GEKO sensitivity by using an Adjoint solver. The objective function defined in this work is based on the linear combination of difference in velocity components, and a Neural Network is trained to obtain an optimized GEKO model. The results with optimized GEKO agree qualitatively and quantitatively with LES and experiments. The generalization of the NN model is tested on different flow conditions, including a range of Reynolds numbers as well as a reacting flow scenario. The results are showing significant improvements over the baseline solution as compared to the experiment. An optimized workflow is established, which can be used in future studies concerning different geometries with similar flow fields.

This paper presents Ansys Fluent laminar–turbulent transition results using the shear stress transport [Formula: see text] model applied to the workshop cases of the First American Institute of Aeronautics and Astronautics Computational Fluid Dynamics (CFD) Transition Modeling Prediction Workshop. The key objectives of this workshop were to assess the current state-of-the-art laminar–turbulent transition models in an industrial Computational Fluid Dynamics environment and to determine and document the best practices to simulate laminar–turbulent transition flows. Sensitivity of the shear stress transport [Formula: see text] model to mesh refinement was established on a zero-pressure-gradient flat plate. Two other cases [a two-dimensional natural laminar flow (NLF) (1)-0416F airfoil, and a scaled Common Research Model (CRM)-NLF aircraft model] were selected as validation cases using a hierarchy of structured and unstructured meshes. Due to the complexity of the geometry and the airflow around the Common Research Model (CRM)- Natural laminar Flow (NLF) aircraft model, mesh adaptation cycles were also conducted to capture the shock, the wake, and the wing-tip vortices produced by the CRM-NLF. The accuracy of the [Formula: see text] model is evaluated using transition location measurements obtained with temperature-sensitive paint, pressure coefficient distributions at multiple wingspan stations, and aerodynamic coefficients at numerous angles of attack. The outcome of these comparisons will provide guidelines to conduct laminar–turbulent transition simulations with the [Formula: see text] model on simple and complex aerospace designs.

A Direct Numerical and Large Eddy Simulation study is conducted to establish the NASA CS0 diffuser as a test case for scale-resolving simulation methods and to evaluate the ability of such simulations to accurately predict flows with adverse pressure gradients and shallow separation from a smooth surface. The results of fine grid studies are in a good agreement with experimental data and substantially supplement them. These data are used as a basis for testing of LES on reduced grids, using different combinations of wall treatments and turbulence model formulations.

A new algebraic RANS model for laminar–turbulent transition will be presented. The model follows the Local-Correlation-based Transition Modeling concept, is Galilean invariant and can handle natural, bypass and separation-induced transition. The model formulation is discussed in detail. A substantial number of test cases have been computed to evaluate the different transition mechanisms of the model.

Accurate numerical prediction of surface heat transfer in the presence of film cooling within aero-engine sub-components, such as blade effusion holes and combustor liners, has long been a goal of the aero-engine industry. It requires accurate simulation of the turbulent mixing and reaction processes between freestream and the cooling flow. In this study, the stress-blended eddy simulation (SBES) turbulence model is used together with the flamelet generated manifold (FGM) combustion model to calculate the surface heat flux upstream and downstream of an effusion cooling hole. The SBES model employs a blending function to automatically switch between Reynolds-averaged Navier–Stokes (RANS) and large eddy simulation (LES) based on the local flow features, and thus significantly reduces the computational cost compared to a full LES simulation. All simulations are run using ansys fluent®, a commercial finite-volume computational fluid dynamics (CFD) solver. The test case corresponds to an experimental rig run at Massachusetts Institute of Technology (MIT), which is essentially a flat plate brushed by a uniform freestream of argon with ethylene seeded inside, and is cooled by either a reacting air or a non-reacting nitrogen jet inclined at 35 deg to the freestream. Calculations are performed for both reacting and non-reacting jet cooling cases across a range of jet-to-stream blowing ratios and compared with the experimental data. The effects of mesh resolution are also investigated. Calculations are also performed across a range of Damköhler number (i.e., flow to chemical time ratio) from zero to 30, with unity blowing ratio, and the differences in the maximum surface heat flux magnitude in the reacting and non-reacting cases at a specific location downstream of the hole are investigated. Results from these analyses show good correlation with the experimental heat flux data upstream and downstream of the cooling hole, including the heat flux augmentation due to local reaction. Results from the Damköhler number sweep also show a good match with the experimental data across the range investigated.

An overview of scale-resolving simulation (SRS) methods used in ANSYS Computational Fluid Dynamics (CFD) software is provided. The main challenges, especially when computing boundary layers in large eddy simulation (LES) mode, will be discussed. The different strategies for handling wall-bound flows using combinations of RANS and LES models will be explained, along with some specific application examples. It will be demonstrated that the stress-blended eddy simulation (SBES) approach is optimal for applications with a mix of boundary layers and free shear flows due to its low cost and its ability to handle boundary layers in both RANS and wall-modeled LES (WMLES) modes.

Large Eddy Simulation with Wall Function (WFLES) is known to be a cheap alternative to classical LES methods for simulation of flow where large and complex computational meshes are typically required. This makes it attractive for engineering applications. However experience of applying such methods to complex turbulent flows with flow separation and reattachment is still little-known in literature. In this work WFLES of flow around simplified car body with slant angle equal to 25 degrees and Re L = 2.8 · 10 6 is carried out on Octree mesh to demonstrate the capabilities and limitations of the method in such type of the flow. The results on a series of meshes show that even though the general flow topology is well captured, the critical part of the flow on the slant is hardly predicted even on 100 mln mesh. It is concluded that the prediction of separation above the slant requires significant mesh refinement even in the frame of WFLES.

The results of using Large Eddy Simulation with Wall Functions (WFLES) in application to basic wall-bounded flows, such as turbulent boundary layer and channel flow cases are presented. In particular, it is shown that WFLES is suitable for predicting wall bounded flows and provides reasonable accuracy when using appropriate grids. The grid for WFLES should have isotropic cells with size smaller than 10% of the boundary layer thickness. Using coarser grids or anisotropic cells leads to significant reduction of accuracy.

Direct numerical simulation (DNS) of the separated flow in axisymmetric CS0 diffuser is conducted. The obtained results are in a good agreement with experimental data of Driver and substantially supplement them. Along with other data, eddy viscosity extracted from performed DNS could be used for RANS turbulence model improvement.

High quality prediction of laminar-turbulent transition for flow around airfoils is an important task for industrial applications. Prediction of such flows is usually carried out using the RANS framework in combination with transition models. The present study shows the capability of a recently developed algebraic transition model for prediction flows around different airfoils. The results of the model demonstrate satisfactory agreement with the experimental data and with results of existing differential models.

This paper presents simulations using the correlation-based SST-ϒ laminar-to-turbulent transition model applied to hypersonic flows. This transition model, available in ANSYS Fluent, includes several previously established empirical correlations to account for a variety of transition mechanisms. The results presented here focus on assessing the performance of the established model implementation and its correlations to hypersonic flow applications on a set of published validation cases with transition: a flat plate at M=11.1 & M=10.6 , and two axisymmetric cone-cylinder-flares at M=7.19 with a blunt nose, and M=7.16 with a sharp nose. This assessment will form the basis for subsequent identification of possible improvements to the transition model’s predictive capability through the implementation of further empirical correlations to account for additional transition mechanisms for hypersonic flows.

The concept behind the development of a new two-equation turbulence model will be discussed. It is designed with free parameters which allow the adjustment of the model to a wide variety of flow conditions without violating the calibration for flat plates. The new model also allows to replace existing models by specific selection of model coefficients. This offers the opportunity for future turbulence model consolidation.

A new global hybrid RANS-LES methodology will be presented. It is intended as replacement for existing models like DES/DDES/IDDES. The new model offers improved shielding of RANS boundary layers, a more rapid RANS-LES ‘transition’, WMLES capabilities as well as modularity with respect to the combination of different RANS and LES formulations.

A detailed investigation of the passage between LES and RANS subdomains for zonal RANS-LES simulations of wall-bounded flows is performed with the main focus on the turbulent quantities reconstruction at LES-RANS interfaces. It is shown, that most accurate results are obtained if the turbulent quantities are specified from a precursor RANS simulation, while employing the actual solution from the LES subdomain is slightly less precise.

The paper presents the results of Improved Delayed Detached Eddy Simulation (IDDES) in combination with wall functions for the wall boundary conditions specification. It is shown that good agreement with the solutions on the conventional grids with \({\Delta } y^{+}_{w}\)<1 can be achieved on grids with wall-normal steps gradually changing between 1 % and 5 % of the boundary layer thickness near the wall and in the core-flow respectively. At the same time, using of coarser grids results in a noticeable discrepancy for the mean and RMS velocity, which is attributed to the lack of the wall-normal resolution rather than to the wall boundary conditions.

Historically, industrial CFD simulations have been based on the Reynolds Averaged Navier-Stokes Equations (RANS). For many decades, the only alternative to RANS was Large-Eddy Simulation (LES), which has however failed to provide solutions for most flows of engineering relevance due to excessive computing power requirements for the simulation of wall-bounded flows.