Detached-Eddy Simulations and Reynolds-Averaged Navier-Stokes Simulations of Delta Wing Vortical Flowfields

Morton, Scott A.; Forsythe, James R.; Mitchell, Anthony; Hajek, D.

doi:10.1115/1.1517570

Cited by 57 publications

(23 citation statements)

References 21 publications

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“…Tomaro et al [63] converted the code from explicit to implicit, enabling Courant-Friedrichs-Lewy numbers as high as 10 6 . The Cobalt solver has been used at the Air Force Seek Eagle Office (AFSEO) and the United States Air Force Academy (US-AFA) for a variety of unsteady nonlinear aerodynamic problems of maneuvering aircraft [13,12,45,14,28].…”

Section: Cfd Solvermentioning

confidence: 99%

Challenges in the aerodynamics modeling of an oscillating and translating airfoil at large incidence angles

Ghoreyshi

Cummings

2013

Aerospace Science and Technology

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The challenges in the modeling of the unsteady lift of a two-dimensional NACA 0012 airfoil oscillating and translating at large incidence angles are investigated in this paper. Forced oscillation motions with two reduced frequency values of 0.1 and 1.0 were used. The CFD results show that a hysteresis loop was developed in the lift variation with angle of attack; shapes of the loops change significantly with reduced frequency value. A dynamic stall vortex was identified in the pitching and plunging motions with k = 0.1.This vortex delays the onset of flow separation over the upper surface to a higher incidence than would occur in steady conditions. The unsteady lift of the very fast motion is enhanced significantly due to the formation of a compression wave on the lower surface and an expansion wave on the upper surface. The results show clear limitations of unsteady aerodynamic theories for modeling motions at high incidences. Also, the CFD solution of indicial functions show a large oscillation at angles of attack beyond the stall angle, but the predictions of a model based on Radial Basis Function matches CFD values quite well.

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Section: Cfd Solvermentioning

confidence: 99%

Challenges in the aerodynamics modeling of an oscillating and translating airfoil at large incidence angles

Ghoreyshi

Cummings

2013

Aerospace Science and Technology

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“…This inability of commonly used turbulence models to accurately compute a solution with breakdown is well documented in the literature and is due to the large amount of eddy-viscosity these models put into the core of vortices. 22 Several researchers have proposed fixes to these turbulence models by incorporating some form of a rotation correction. The disadvantage of this approach is the fact the simulation will still be operating in a RANS mode and compute solutions that are relatively steady post-breakdown as opposed to an LES approach that resolves the eddies that produce the unsteadiness.…”

Section: A Comparison Of Various Turbulence Modelsmentioning

confidence: 99%

“…The primary advantage of DES is that it can be applied at high Reynolds numbers, as can Reynolds-averaged techniques, but DES also resolves geometry-dependent, unsteady threedimensional turbulent motions as in LES. The unstructured finite-volume solver Cobalt 20 has been used in conjunction with DES successfully on a number of complex problems, including a supersonic base flow, 21 delta wing vortex breakdown, 22 a square with rounded corners, 23 the F-15E at high angle of attack, 24 and the F/A-18E with unsteady shock buffet. 25 The specific aim of this work is to document the effects of applying detached eddy simulations to the F/A-18C at a condition consistent with vortex breakdown.…”

Section: Aiaa 2004-1676mentioning

confidence: 99%

High Resolution Turbulence Treatment of F/A-18 Tail Buffet

Morton

Cummings

Kholodar

2007

Journal of Aircraft

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“…As a result, all spectral effects are lost in the time averaging process. The unsteady variant of this, URANS, although managing to resolve non-stationary mean flows, will produce too much eddy viscosity polluting the predicted fields [1,2]. For many turbulent flows of engineering importance, traditional RANS or URANS modeling may be an awkward approach or may fail to reproduce the relevant flow physics.…”

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confidence: 99%

Towards an entropy-based detached-eddy simulation

Zhao

Yan

et al. 2013

Sci. China Phys. Mech. Astron.

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A concept of entropy increment ratio ( s ) is introduced for compressible turbulence simulation through a series of direct numerical simulations (DNS). s represents the dissipation rate per unit mechanical energy with the benefit of independence of freestream Mach numbers. Based on this feature, we construct the shielding function f s to describe the boundary layer region and propose an entropy-based detached-eddy simulation method (SDES). This approach follows the spirit of delayed detached-eddy simulation (DDES) proposed by Spalart et al. in 2005, but it exhibits much better behavior after their performances are compared in the following flows, namely, pure attached flow with thick boundary layer (a supersonic flat-plate flow with high Reynolds number), fully separated flow (the supersonic base flow), and separated-reattached flow (the supersonic cavity-ramp flow). The Reynolds-averaged Navier-Stokes (RANS) resolved region is reliably preserved and the modeled stress depletion (MSD) phenomenon which is inherent in DES and DDES is partly alleviated. Moreover, this new hybrid strategy is simple and general, making it applicable to other models related to the boundary layer predictions. Advances in computer speeds have made it possible to utilize more accurate methods of simulating and modeling turbulent flows. However, grid requirements and time cost typically restrict direct numerical simulation (DNS) and even large eddy simulation (LES) to only low Reynolds numbers. That is, Reynolds-averaged Navier-Stokes (RANS) equations along with a turbulence model seem still to be a powerful tool for engineering aerodynamic analysis nowadays, whereas, traditional RANS approaches do not resolve any turbulent flow structures, but model the effect of turbulence on the mean flow in terms of representative mean turbulence scales. As a result, all spectral effects are lost in the time averaging process. The unsteady variant of this, URANS, although managing to resolve non-stationary mean flows, will produce too much eddy viscosity polluting the predicted fields [1,2]. For many turbulent flows of engineering importance, traditional RANS or URANS modeling may be an awkward approach or may fail to reproduce the relevant flow physics. Hybrid RANS/LES approaches [3] represent a credible alternative improving the description of such flows at a reasonable cost by taking into account most of the flow unsteadiness. The main idea of these methods is to model the turbulent structures in the attached region of the flow and to solve the large length-scale structures elsewhere. One of the most popular RANS/LES methods is the detached-eddy simulation proposed by Spalart et al. in 1997 [4] (termed in the following as DES97), which is based on a modification of the length scale employed by Spalart-Allmaras RANS model (SA) [5]. Since the time it was put forward, DES97 has been applied successfully to numerous engineering flow problems, especially in high-Reynolds number separated

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Detached-Eddy Simulations and Reynolds-Averaged Navier-Stokes Simulations of Delta Wing Vortical Flowfields

Cited by 57 publications

References 21 publications

Challenges in the aerodynamics modeling of an oscillating and translating airfoil at large incidence angles

Challenges in the aerodynamics modeling of an oscillating and translating airfoil at large incidence angles

High Resolution Turbulence Treatment of F/A-18 Tail Buffet

Towards an entropy-based detached-eddy simulation

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