Numerical investigation of tail buffet on F-18 aircraft

Rizk, Yehia M.; Guruswamy, Guru P.; Gee, Ken

doi:10.2514/6.1992-2673

Cited by 24 publications

(6 citation statements)

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“…Simplistic grid zone mapping, which places each grid zone into a separate processor, leads to inefficient parallel performance because it does not incorporate load balancing. The efficiency percentage factor, e, due to lack of load balancing can be expressed as e = 100t /{p*m*r} (2) where t is the total grid size, m is the number of processors used, p is the optimum grid size per processor, and r is the ratio of largest to smallest grid size. For the configuration shown in Figure 8, the efficiency is 6 percent where the optimum size per processor is 300K grid points on an Origin2000 system.…”

Section: Load Balancingmentioning

confidence: 99%

“…Although these low-fidelity approaches are computationally less intensive, they are not adequate for the analysis of aircraft that can experience complex flow-structure interactions. Examples of such complex interactions include the vortex-induced aeroelastic oscillations of the B-1 aircraft [1], structural oscillations of the F-18A's vertical tails due to the burst of leading edge vortices [2], buffet-associated structural oscillations [3] and dips in flutter speed [4] experienced by aircraft that fly in the transonic regime, and abrupt wing stall experienced by modern fighters such as the F/A 18E aircraft that can be dominated by unsteady flows possibly associated with aeroelastic oscillations [5]. High-fidelity equations, such as the Euler/Navier-Stokes (ENS) for fluids and the finite-element method (FEM) for structures, are needed to produce accurate aeroelasticity computations for situations involving these complex fluid/structure interactions.…”

Section: Introductionmentioning

confidence: 99%

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An Evaluation on the Efficient use of Supercomputers for Computational Aeroelasticity

Guruswamy¹

2009

International Journal of Aerospace Innovations

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This study evaluates the role of supercomputers in large-scale fluid/structure analyses of aerospace vehicles, with an emphasis on computational aeroelasticity dominated by complex fluid/structure interactions. The information presented is primarily based on responses to a web-based survey that was designed to capture the nuances of highperformance computational aeroelasticity and, in particular, its use of parallel computers. Survey responses were solicited from leading application engineers who use NASA and DoD supercomputing resources. A method of assigning a fidelity-complexity index (FCI) to each application is presented, and case studies of major applications using HPC resources are summarized.

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Section: Load Balancingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An Evaluation on the Efficient use of Supercomputers for Computational Aeroelasticity

Guruswamy¹

2009

International Journal of Aerospace Innovations

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“…Rizk et al 9,10 solved the Reynolds-averaged, thin-layer Navier-Stokes equations around the F/A-18 aircraft at α = 30 deg. A chimera embedded grid consisting of 0.9 million cells was used to model the symmetric half of the aircraft.…”

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confidence: 99%

Alleviation of Vertical Tail Buffeting of F/A-18 Aircraft

Sheta

2004

Journal of Aircraft

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A high-fidelity multidisciplinary computational investigation for the prediction of buffet characteristics and buffet alleviation of the vertical tail of full F/A-18 aircraft is conducted and presented. Alleviation of the vertical tail buffeting is achieved using streamwise wing fences. The problem is solved using four sets of high-fidelity analysis modules. The Reynolds-averaged full Navier-Stokes equations are solved for the aerodynamic flowfield. The structural dynamic responses of the vertical tail are computed using direct finite element analysis. The fluidstructure interfacing is modeled using conservative and consistent interfacing module. A transfinite interpolation algorithm is used to deform the computational grid dynamically to accommodate the deformed shape of the vertical tail. The investigation is conducted over a wide range of high angles of attack at a Mach number of 0.243 and a Reynolds number of 11 × × 10 6 . The LEX fences shift the onset of maximum buffet condition to higher angles of attack. The LEX fences also reduce the root-mean-square values of differential pressure and root bending moment. At 30-deg angle of attack, the acceleration power of the vertical tail tip is reduced by up to 38% at first bending mode and by up to 24% at first torsion mode. However, the effectiveness of the LEX fences for buffet alleviation is reduced for very high angles of attack. Nomenclature A t= reference area of vertical tail, 4.842 m 2 C P = coefficient of pressure, (P − P ∞ )/q ∞ C rbm = root bending moment coefficient, M B /q ∞ A tC C = mean aerodynamic chord of the wing, 3.5 m C P = mean pressure coefficient,dimensionless buffet pressure power spectral densitŷ F i = inviscid flux vector F v = viscous flux vector f = frequency, Hz M B = vertical tail root bending moment N = number of sample points n = nondimensional frequency, fC/U ∞ P i = pressure on inboard tail surface P o = pressure on outboard tail surfacê Q = vector of conservative variables q ∞= freestream dynamic pressure U ∞ = freestream velocity α = angle of attack P = differential pressure, P i − P o

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“…The aerodynamic loads were more sensitive to the chordwise tail location than its spanwise location. Numerical investigation of bu!et problem has been conducted by Rizk et al (1992) and Gee et al (1995) for F/A-18 model, and by Findlay (1997) and Morton et al (1998) for delta-wing/twin-tail model using Reynolds-averaged, thin-layer Navier}Stokes equations. A weak coupling between the structures and aerodynamics are considered in these studies by assuming only rigid tails.…”

Section: Introductionmentioning

confidence: 99%