A generalised wall function including compressibility and pressure-gradient terms for the Spalart–Allmaras turbulence model

Joshi, Amit M.; Assam, Ashwani; Nived, M. R.; Eswaran, V.

doi:10.1080/14685248.2019.1691730

Cited by 13 publications

(5 citation statements)

References 20 publications

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“…The large domain size and high Reynolds number made the resolution of y + near the value of 1, impossible. However, the average y + values were kept under 25 because the automatic wall function used for the simulations provides reasonable results when compared to the experimental data [28]. In the unsteady simulations, the advection term was first discretized using the upwind advection scheme to achieve convergence faster.…”

Section: ∂(ρK) ∂Tmentioning

confidence: 99%

Numerical Simulation and Experimental Validation of a Kaplan Prototype Turbine Operating on a Cam Curve

Iovănel

Dehkharqani²,

Bucur

et al. 2022

Energies

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The role of hydropower has become increasingly essential following the introduction of intermittent renewable energies. Quickly regulating power is needed, and the transient operations of hydropower plants have consequently become more frequent. Large pressure fluctuations occur during transient operations, leading to the premature fatigue and wear of hydraulic turbines. Investigations of the transient flow phenomena developed in small-scale turbine models are useful and accessible but limited. On the other hand, experimental and numerical studies of full-scale large turbines are challenging due to production losses, large scales, high Reynolds numbers, and computational demands. In the present work, the operation of a 10 MW Kaplan prototype turbine was modelled for two operating points on a propeller curve corresponding to the best efficiency point and part-load conditions. First, an analysis of the possible means of reducing the model complexity is presented. The influence of the boundary conditions, runner blade clearance, blade geometry and mesh size on the numerical results is discussed. Secondly, the results of the numerical simulations are presented and compared to experimental measurements performed on the prototype in order to validate the numerical model. The mean torque and pressure values were reasonably predicted at both operating points with the simplified model. An analysis of the pressure fluctuations at part load demonstrated that the numerical simulation captured the rotating vortex rope developed in the draft tube. The frequencies of the rotating and plunging components of the rotating vortex were accurately captured, but the amplitudes were underestimated compared to the experimental data.

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Section: ∂(ρK) ∂Tmentioning

confidence: 99%

Numerical Simulation and Experimental Validation of a Kaplan Prototype Turbine Operating on a Cam Curve

Iovănel

Dehkharqani²,

Bucur

et al. 2022

Energies

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“…The implementations of the three fully turbulent RANS models in the PRAVAHA solver have been validated in previous work (Joshi et al , 2019; Sharma et al , 2020; Kalkote et al , 2019). The validation of the SA-BCM transition model implementation in the solver is presented below prior to the results of the airfoil stall simulations.…”

Section: Resultsmentioning

confidence: 99%

“…All the RANS simulations shown in this study are performed on the Pravaha solver, which is an in-house unstructured grid finite-volume compressible flow solver developed by the authors’ research group at IIT Hyderabad (Joshi et al , 2019; Kalkote et al , 2019; Assam, 2019). The implicit solver has been equipped with an all-speed algorithm with low Mach preconditioning (Weiss et al , 1999) that allows the simulation of flows in the incompressible regime using the compressible form of the Navier–Stokes (NS) equations.…”

Section: Base Solver and Governing Equationsmentioning

confidence: 99%

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On the performance of RANS turbulence models in predicting static stall over airfoils at high Reynolds numbers

Nived

Mukesh

Athkuri

et al. 2021

HFF

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Purpose This paper aims to conduct, a detailed investigation of various Reynolds averaged Navier–Stokes (RANS) models to study their performance in attached and separated flows. The turbulent flow over two airfoils, namely, National Advisory Committee for Aeronautics (NACA)-0012 and National Aeronautics and Space Administration (NASA) MS(1)-0317 with a static stall setup at a Reynolds number of 6 million, is chosen to investigate these models. The pre-stall and post-stall regions, which are in the range of angles of attack 0°–20°, are simulated. Design/methodology/approach RANS turbulence models with the Boussinesq approximation are the most commonly used cost-effective models for engineering flows. Four RANS models are considered to predict the static stall of two airfoils: Spalart–Allmaras (SA), Menter’s k – ω shear stress transport (SST), k – kL and SA-Bas Cakmakcioglu modified (BCM) transition model. All the simulations are performed on an in-house unstructured-grid compressible flow solver. Findings All the turbulence models considered predicted the lift and drag coefficients in good agreement with experimental data for both airfoils in the attached pre-stall region. For the NACA-0012 airfoil, all models except the SA-BCM over-predicted the stall angle by 2°, whereas SA-BCM failed to predict stall. For the NASA MS(1)-0317 airfoil, all models predicted the lift and drag coefficients accurately for attached flow. But the first three models showed even further delayed stall, whereas SA-BCM again did not predict stall. Originality/value The numerical results at high Re obtained from this work, especially that of the NASA MS(1)-0317, are new to the literature in the knowledge of the authors. This paper highlights the inability of RANS models to predict the stall phenomenon and suggests a need for improvement in modeling flow physics in near- and post-stall flows.

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“…However, the standard wall-function method, as is usually employed, has limitations for flow cases that involve high adverse pressure gradients and compressibility. The examination of more sophisticated wall-function approaches for the SA turbulence model, which were recently developed, e.g., [25], is deferred to future research.…”

Section: Methodsmentioning

confidence: 99%

Computational Evaluation of Control Surfaces Aerodynamics for a Mid-Range Commercial Aircraft

et al. 2020

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Computational fluid dynamics is employed to predict the aerodynamic properties of the prototypical trailing-edge control surfaces for a small, regional transport, commercial aircraft. The virtual experiments are performed at operational flight conditions, by resolving the mean turbulent flow field around a realistic model of the whole aircraft. The Reynolds-averaged Navier–Stokes approach is used, where the governing equations are solved with a finite volume-based numerical method. The effectiveness of the flight control system, during a hypothetical conceptual pre-design phase, is studied by conducting simulations at different angles of deflection, and examining the variation of the aerodynamic loading coefficients. The proposed computational modeling approach is verified to have good practical potential, also compared with reference industrial data provided by the Leonardo Aircraft Company.

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A generalised wall function including compressibility and pressure-gradient terms for the Spalart–Allmaras turbulence model

Cited by 13 publications

References 20 publications

Numerical Simulation and Experimental Validation of a Kaplan Prototype Turbine Operating on a Cam Curve

Numerical Simulation and Experimental Validation of a Kaplan Prototype Turbine Operating on a Cam Curve

On the performance of RANS turbulence models in predicting static stall over airfoils at high Reynolds numbers

Computational Evaluation of Control Surfaces Aerodynamics for a Mid-Range Commercial Aircraft

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