Masahito Yonezawa

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

The “supersonic biplane theory” has been proposed in order to reduce the sonic boom in supersonic flight. This theory can be realized at a certain design Mach number, but it cannot be performed at off-design ones. Therefore, some innovations and multidisciplinary design optimization are strongly required to improve the off-design performance. At first, the aerodynamic characteristics around biplanes as a baseline configuration have to be analyzed in order to contribute to the conceptual design of the supersonic biplane. Especially, CFD analyses can produce effective results for the flow phenomena to be captured comprehensively; however, they have to be validated by experimental results. The purpose of this study is to demonstrate experimentally the shock wave interference and cancellation between the wings of biplanes based on the “supersonic biplane theory”. Supersonic and transonic flow fields around the biplanes are also examined by CFD analyses and experimental results. This interdisciplinary data will hopefully assist in the effective conceptual design and multi-objective design exploration (MODE) of the supersonic biplane in the near future.

A Study of Busemann-type Biplane for Avoiding Choked Flow

§This study establishes methods to overcome choked-flow and flow-hysteresis problems of Busemann biplane at off-design conditions. Two-dimensional (2-D) analyses of three Busemann-type biplanes have been addressed, using the application of Computational Fluid Dynamics (CFD) code in inviscid flow (Euler) mode. These biplane configurations are designed in such a way that the front streamline area and the rear streamline area can be changed with the use of leading- and trailing-edge flaps (similar to high-lift devices). In this paper, the individual effects of the change in each area on choked-flow and flow-hysteresis are studied in detail. Also, the combined effect of the two is investigated. The results of these analyses show the solutions that are highly capable of overcoming these problems. Nomenclature Ai = area of inlet At

Reducing drag penalty in the three-dimensional supersonic biplane

Abstract The two-dimensional (2D) supersonic biplane is well known for its shock wave cancellation effect and zero wave drag at supersonic speed. Nonetheless, in a three-dimensional (3D) setting, this favourable shock wave interaction becomes disturbed in the Mach cone regions at the wing tips of the supersonic biplane, which results in a severe drag penalty near the wing tips. However, this can be alleviated by appropriately designing the planform of the biplane. This study was performed to investigate the patterns of the 3D shock wave interaction using computational fluid dynamics by considering the 3D supersonic biplane with different planforms. The drag was shown to become large when the wing has a high sweepback angle, and it became small when the wing has a small taper ratio. However, an excessively low taper ratio could also lead to a drag greater than that of the rectangular supersonic biplane. It was found that the low drag 3D supersonic biplane has a small sweepback angle and an adequate taper ratio, which results in the vertex line becoming almost perpendicular to the freestream. Thus, in the design of the low drag 3D supersonic biplane, it is important to take into consideration the trade-off between the drag reduction at the mid-span section and the drag penalty near the wing tip and the wing root.

Wind Tunnel Testing on Start/Unstart Characteristics of Finite Supersonic Biplane Wing

This study describes the start/unstart characteristics of a finite and rectangular supersonic biplane wing. Two wing models were tested in wind tunnels with aspect ratios of 0.75 (model A) and 2.5 (model B). The models were composed of a Busemann biplane section. The tests were carried out using supersonic and transonic wind tunnels over a Mach number range of with angles of attack of 0°, 2°, and 4°. The Schlieren system was used to observe the flow characteristics around the models. The experimental results showed that these models had start/unstart characteristics that differed from those of the Busemann biplane (two dimensional) owing to three-dimensional effects. Models A and B started at lower Mach numbers than the Busemann biplane. The characteristics also varied with aspect ratio: model A () started at a lower Mach number than model B () owing to the lower aspect ratio. Model B was located in the double solution domain for the start/unstart characteristics at , and model B was in either the start or unstart state at . Once the state was determined, either state was stable.

Aerodynamic Performance of the Three-Dimensional Lifting Supersonic Biplane

This paper investigates the aerodynamic performance of the three-dimensional lifting supersonic biplane and its sonic boom. Although the Busemann biplane is known to cancel the wave drag, it does not produce lift, either. A few decades later, the supersonic biplane airfoils with lift were reported. This paper extends their ideas to the three-dimensional biplane. The aerodynamic performance was revealed by using computational fluid dynamics. The possibility of sonic boom mitigation due to shock wave interaction was demonstrated.

Toward silent supersonic transport—A fundamental study of supersonic biplane

In this research, aerodynamic design of biplane airfoils in supersonic flight is discussed based on computational fluid dynamics (CFD). In supersonic flight, airfoils generate strong sonic booms and wave drags accompanied by shock waves. New airfoil geometries which significantly reduce shock waves using a biplane concept will be proposed. The background of this concept originates from Busemann biplane and Licher type biplane concepts. In order to focus on the shock‐wave characteristics around biplane configuration, inviscid flow (Euler) analyses are performed (which are particularly suitable for wave drag analyses). For the evaluation of the reduction level of shock waves, the wave drag coefficient is used. The design Mach number is 1.7. The aerodynamic design is conducted using an iterative inverse design method that is newly implemented. A biplane configuration with a desired performance has been obtained. Having total maximum thickness ratio of 0.10, it has the lift‐to‐wave‐drag ratio of 21.7 at a des...