Re-evaluation of an Optimized Second Order Backward Difference (BDF2OPT) Scheme for Unsteady Flow Applications

Vatsa, Veer N.; Carpenter, Mark H.; Lockard, David P.

doi:10.2514/6.2010-122

“…A variety of time marching schemes are available in FUN3D, including a second-order backward-differencing formulation (BDF2), and an optimized second order backward differencing formulation (BDF2OPT). The BDF2OPT scheme, 26 which produces lower truncation error compared to the standard BDF2 scheme at nominally the same computational cost but with slightly increased memory usage, was chosen for the current application.…”

mentioning

confidence: 99%

Aeroacoustic Simulation of a Nose Landing Gear in an Open Jet Facility using FUN3D

Vatsa

¹

,

Lockard

²

,

Khorrami

³

et al. 2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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Numerical simulations have been performed for a partially-dressed, cavity-closed nose landing gear configuration that was tested in NASA Langley's closed-wall Basic Aerodynamic Research Tunnel (BART) and in the University of Florida's open-jet acoustic facility known as UFAFF. The unstructured-grid flow solver, FUN3D, developed at NASA Langley Research center is used to compute the unsteady flow field for this configuration. A hybrid Reynolds-averaged Navier-Stokes/large eddy simulation (RANS/LES) turbulence model is used for these computations. Time-averaged and instantaneous solutions compare favorably with the measured data. Unsteady flowfield data obtained from the FUN3D code are used as input to a Ffowcs Williams-Hawkings noise propagation code to compute the sound pressure levels at microphones placed in the farfield. Significant improvement in predicted noise levels is obtained when the flowfield data from the open jet UFAFF simulations is used as compared to the case using flowfield data from the closed-wall BART configuration.

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“…For these simulations, 15 subiterations per time-step were used, which was adequate to obtain at least 3 orders of magnitude reduction in the residuals of the governing equations. An optimized second-order backward differencing formulation (BDF2OPT) scheme 18 was chosen for the current work. This scheme produces higher temporal accuracy compared to the standard second-order backward differencing scheme at nominally the same computational cost but with slightly increased memory usage.…”

Section: Governing Equations and Flow Solvermentioning

confidence: 99%

Aeroacoustic Simulation of Nose Landing Gear on Adaptive Unstructured Grids with FUN3D

Vatsa

¹

,

Khorrami

²

,

Park

³

et al. 2013

19th AIAA/CEAS Aeroacoustics Conference

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Numerical simulations have been performed for a partially-dressed, cavity-closed nose landing gear configuration that was tested in NASA Langley's closed-wall Basic Aerodynamic Research Tunnel (BART) and in the University of Florida's open-jet acoustic facility known as the UFAFF. The unstructured-grid flow solver FUN3D, developed at NASA Langley Research center, is used to compute the unsteady flow field for this configuration. Starting with a coarse grid, a series of successively finer grids were generated using the adaptive gridding methodology available in the FUN3D code. A hybrid Reynolds-averaged Navier-Stokes/large eddy simulation (RANS/LES) turbulence model is used for these computations. Time-averaged and instantaneous solutions obtained on these grids are compared with the measured data. In general, the correlation with the experimental data improves with grid refinement. A similar trend is observed for sound pressure levels obtained by using these CFD solutions as input to a Ffowcs Williams-Hawkings noise propagation code to compute the farfield noise levels. In general, the numerical solutions obtained on adapted grids compare well with the hand-tuned enriched fine grid solutions and experimental data. In addition, the grid adaption strategy discussed here simplifies the grid generation process, and results in improved computational efficiency of CFD simulations. Nomenclature BARTBasic Aerodynamic Research Tunnel BDF2OPT optimized second-order backward differencing formulation CFD computational fluid dynamics C p

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“…Node-based conservative variables are computed by driving a 2nd-order accurate spatial residual to steady-state with a point-implicit iterative method. A modified, optimum 2nd-order backward difference formula (BDF) scheme is used in conjunction with a temporal error controller that assured design order [29]. OVERFLOW OVERFLOW 2 is an implicit Navier-Stokes flow solver that uses structured overset grids.…”

Section: Fun3dmentioning

confidence: 99%

Supersonic retropropulsion CFD validation with Ames Unitary Plan Wind Tunnel test data

Schauerhamer

¹

,

Zarchi

²

,

Kleb

³

et al. 2013

2013 IEEE Aerospace Conference

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Abstract-A validation study of Computational Fluid Dynamics (CFD) for Supersonic Retropropulsion (SRP) was conducted using three Navier-Stokes flow solvers (DPLR, FUN3D, and OVERFLOW). The study compared results from the CFD codes to each other and also to wind tunnel test data obtained in the NASA Ames Research Center 9 ×7 Unitary Plan Wind Tunnel. Comparisons include surface pressure coefficient as well as unsteady plume effects, and cover a range of Mach numbers, levels of thrust, and angles of orientation. The comparisons show promising capability of CFD to simulate SRP, and best agreement with the tunnel data exists for the steadier cases of the 1-nozzle and high thrust 3-nozzle configurations.

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Re-evaluation of an Optimized Second Order Backward Difference (BDF2OPT) Scheme for Unsteady Flow Applications

Cited by 88 publications

References 30 publications

Aeroacoustic Simulation of a Nose Landing Gear in an Open Jet Facility using FUN3D

Aeroacoustic Simulation of a Nose Landing Gear in an Open Jet Facility using FUN3D

Aeroacoustic Simulation of Nose Landing Gear on Adaptive Unstructured Grids with FUN3D

Supersonic retropropulsion CFD validation with Ames Unitary Plan Wind Tunnel test data

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