Numerical Simulation of CUBRC Wake Flow Experiments Using a Hybrid LES/RANS Approach

Salazar, Giovanni; Edwards, Jack R.

doi:10.2514/6.2013-307

Cited by 2 publications

(1 citation statement)

References 25 publications

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“…Salazar [27] introduced a grid correction function in the definition of length scale ratio (3) so as to take grid resolution into consideration while determining the RANS to LES transition. With Salazar's fix, the length scale ratio is redefined as…”

Section: Hybrid Les/rans Models and Numerical Methodsmentioning

confidence: 99%

RANS and LES/RANS Simulations of Flow Over an Dynamically Pitching Naca0012 Airfoil

Edwards

2015

53rd AIAA Aerospace Sciences Meeting

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The hybrid Large-Eddy/Reynolds-Averaged Navier-Stokes (LES/RANS) and RANS simulations are used to investigate the properties of subsonic flow over NACA 0012 airfoils undergoing static and dynamic stall conditions (M=0.1, α=16.7°, Re c =1.0×10 6 ). In the simulations of NACA 0012 airfoil at static stall case, Menter's SST model predicts an attached flow at the leading edge, whereas the Gieseking's LES/RANS model on a coarser mesh predicts a massively separated flow characterized by the stabilization of a detached leading edge vortex near the trailing edge. The predictions by Gieseking's model on a coarse mesh agree closely with PIV measurements of mean velocity, the Reynolds axial stress and the Reynolds normal stress, but over-predict the magnitude of the Reynolds shear stress. However, Gieseking's model on a fine mesh predicts a more attached flow because the under-resolved LES on the fine mesh (but not fine enough as required in a wall-resolved LES) fails to reproduce the cascade process at the smaller scale and results in an overlyenergetic boundary layer near leading edge which resists and delays the separation. In 3D simulations of dynamic stall case where the NACA 0012 airfoil is dynamically pitching about its quarter-chord at a reduced frequency, k r =0.1, Gieseking's model on a coarse mesh in spanwise direction correctly predicts response of the massive separation at static stall angle of 16.7° during downstroke pitching, but it also predicts some leading edge separation which is not present in the experiment during upstroke pitching. Mesh refinement in the spanwise direction helps reducing the level of leading edge separation during upstroke pitching, but results in an under-separated flow solution for downstroke response, which is consistent with what happens in the static stall case and the reason is also similar. By introducing a grid correction function in the definition of outer layer turbulence length scale, Salazar's fix takes grid resolution into consideration while determining the RANS to LES transition. The inclusion of Salazar's fix to Gieseking's model delays the leading edge separation during upstroke pitching, but it also introduces a too-attached flow for downstroke response. Nomenclature c = airfoil chord C N = model constant for blending function in Gieseking's model C s = model constant (sharpening factor) in Gieseking's model  C = model constant in Menter SST turbulence f = pitching frequency k = turbulent kinetic energy k r = reduced frequency L = representative length scale l inner = inner layer turbulent length scale l outer = outer layer turbulent length scale M = Mach number = freestream pressure Re c = chord Reynolds number S = magnitude of strain rateAIAA SciTech T = temperature u, v, w = velocity in x, y, z directions = freestream velocity x/c = axial distance over axial chord = angle of attack = blending function for LES/RANS eddy viscosity = density = ratio of turbulence length scale = molecular viscosity = eddy viscosity = specific turbulence dissipation rate = magnitude of...

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Section: Hybrid Les/rans Models and Numerical Methodsmentioning

confidence: 99%

RANS and LES/RANS Simulations of Flow Over an Dynamically Pitching Naca0012 Airfoil

Edwards

2015

53rd AIAA Aerospace Sciences Meeting

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Orion MPCV Continuum RCS Heating Augmentation Model Development

Hyatt

White

2014

52nd Aerospace Sciences Meeting

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The reaction control system jets of the Orion Multi Purpose Crew Vehicle can have a significant impact on the magnitude and distribution of the surface heat flux on the leeside of the aft-body, when they are fired. Changes in surface heating are expressed in terms of augmentation factor over the baseline smooth body heating. Wind tunnel tests revealed heating augmentation factors as high as 13.0, 7.6, 2.8, and 5.8 for the roll, pitch down, pitch up, and yaw jets respectively. Heating augmentation factor models, based almost exclusively on data from a series of wind tunnel tests have been developed, for the purposes of thermal protection system design. The wind tunnel tests investigated several potential jet-to-freestream similarity parameters, and heating augmentation factors derived from the data showed correlation with the jet-to-freestream momentum ratio. However, this correlation was not utilized in the developed models. Instead augmentation factors were held constant throughout the potential trajectory space. This simplification was driven by the fact that ground to flight traceability and sting effects are not well understood. Given the sensitivity of the reaction control system jet heating augmentation to configuration, geometry, and orientation the focus in the present paper is on the methodology used to develop the models and the lessons learned from the data. The models that are outlined in the present work are specific to the aerothermal database used to design the thermal protection system for the Exploration Flight Test 1 vehicle.

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Numerical Simulation of CUBRC Wake Flow Experiments Using a Hybrid LES/RANS Approach

Cited by 2 publications

References 25 publications

RANS and LES/RANS Simulations of Flow Over an Dynamically Pitching Naca0012 Airfoil

RANS and LES/RANS Simulations of Flow Over an Dynamically Pitching Naca0012 Airfoil

Orion MPCV Continuum RCS Heating Augmentation Model Development

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