Experimental and Computational Fluid Dynamics Around Supersonic Biplane for Sonic-Boom Reduction

2009

Journal of Aircraft

Self Cite

This study describes the nondeterministic effect of homogeneous atmospheric turbulence on sonic boom propagation. The Sears-Haack body was calculated in three dimensions by computational fluid dynamics in inviscid flow (Euler) mode to create the near-field pressure wave. The homogeneous atmospheric turbulence field was represented by the finite sum of discrete Fourier modes based on the von Karman and Pao energy spectrum. The sonic boom signature was then calculated by the modified waveform parameter method, considering a random velocity of homogeneous atmospheric turbulence. The results of this study indicated that atmospheric turbulence has a marked influence on sonic boom overpressure during its propagation to the ground. In comparison to the noturbulence condition, we found that the sonic boom decreased in 59% of the cases and increased in 41% of the cases. Thus, homogeneous atmospheric turbulence seems to favor a decrease, rather than an increase, in boom overpressure. In addition, we found that turbulence has a small effect on the propagation path from the flight altitude to the ground. Nonetheless, this small change in the propagation path may result in a variability, of the point at which the sonic boom reaches the ground, of up to 1820 ft in the north-south direction (flight direction) and 115 ft in the east-west direction.

Section: Doi: 102514/140215mentioning

confidence: 99%

Sonic Boom Variability Due to Homogeneous Atmospheric Turbulence

Yamashita

2009

Journal of Aircraft

Self Cite

“…However, these methods must be validated by experiment to capture the flow phenomena comprehensively. [13][14][15] These previous studies on aerodynamic performance focused on the supersonic and transonic range. However, the performance in a low-speed range has not been consid-…”

Section: Introductionmentioning

confidence: 99%

Experimental and Computational Studies of Low-Speed Aerodynamic Performance and Flow Characteristics around a Supersonic Biplane

Kuratani

Ozaki

Trans. Japan Soc. Aero. S Sci.

et al. 2009

Self Cite

One of the most critical technical issues with regard to supersonic commercial transportation is the sonic boom that occurs during supersonic cruising flight, which causes impulsive noise on the ground. The ''supersonic biplane theory'' has been proposed to reduce the sonic boom. Shock wave interaction and cancellation between the wings of a supersonic biplane can be realized at a specific design Mach number, but does not work at off-design values. Here, the low-speed aerodynamic performance, as off-design performance, of a baseline supersonic biplane was investigated and discussed using experimental and computational fluid dynamics approaches. The thin airfoil stall characteristics of a supersonic biplane were shown to be caused by the stall of both upper and lower wings at an angle of attack of 20. Although there was leading flow separation of the upper wing at lower angles of attack, the stall of the lower wing was suppressed by interference with the upper wing. The lift of the lower wing was almost dominant to produce the lift of the supersonic biplane in the low-speed range. However, the lower wing caused greater drag than the upper wing at higher angles of attack.

“…D ps is the distance from the location of pixel shift, H[N] is the step function, SFRW is the step function response width, and IW(a) is the interrogation window, with a being its value in pixels. For IW (32,16,8), multipass evaluation was carried out. of dots.…”

Section: Image Evaluationmentioning

confidence: 99%

“…Smoke based visulaization in combination with force measurements has also been applied, with the aim to investigate the biplane behaviour at liftoff or nondesign conditions, [9,10]. The pressure distribution on the surface of the biplane has been experimentally measured by pressure and temperature sensitive paints, [7,8,11], and in the work of Saito et al some boundary layer effects were observed. Concluding remarks common to all these experiments are that, in general, flow field matches well with CFD predictions, but quantitative 3D (even 2D) measurea e-mail: gojani@edge.ifs.tohoku.ac.jp ments are still required, and that biplane model supporting mechanisms in wind tunnels interefere with the overall flow.…”

Section: Introductionmentioning

confidence: 99%

“…Applications of these two methods make the bulk of recent experiments, as well. Qualitative flow characteristics, mainly the effect of shock wave -expansion wave interference, are obtained indirectly by using schlieren visualization on wind tunnels, and the resulting images are later compared to CFD calculations, [6][7][8][9]. Smoke based visulaization in combination with force measurements has also been applied, with the aim to investigate the biplane behaviour at liftoff or nondesign conditions, [9,10].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Review of background oriented schlieren and development for ballistic range applications

Gojani

Kamishi

2013

EPJ Web of Conferences

Self Cite

Abstract. Quantitative measurements of fluid flow can be achieved by flow visualization techniques, and this paper reviews and outlines background oriented schlieren, with emphasis on its performance: measurement sensitivity and uncertainty. Since the technique depends on cross-correlation, an assessment of image evaluation is also conducted. Background oriented schlieren is applied to two flows: shock reflection from a wedge in a shock tube, and natural cooling by convection. It is estimated that the technique can be applied to ballistic facilities.