Daigo Maruyama

Aerodynamic Design of Biplane Airfoils for Low Wave Drag Supersonic Flight

In this paper, 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. We propose a significant reduction of them, especially wave drags using a biplane-airfoil concept. The background of this concept is originated 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 is particularly suitable for wave drag analyses). Design Mach number is 1.7. The aerodynamic design is conducted using an iterative inverse design method that is newly implemented. A biplane configuration having a desired performance has been obtained. Having 0.102 of total maximum thickness ratio (t/c), it has the lift to wave drag ratio (L/D) of 21.7 at a desired lift condition for supersonic flight, lift coefficient (Cl)=0.115. At the range of lift coefficient more than 0.144 this designed biplane has lower wave drag than that of a (zero-thickness) single flat plate airfoil.

Three-Dimensional Aerodynamic Design of Low-Wave-Drag Supersonic Biplane Using Inverse Problem Method

In supersonic flight, airfoils generate strong sonic boom and wave drag accompanied by shock waves and expansion waves. The Busemann biplane is representative of an airfoil that has the possibility of realizing low drag. With the aim of realizing a new concept of supersonic transport, aerodynamic design and analysis are discussed based on computational fluid dynamics. Traditional biplane airfoils were extended to three-dimensional wings with a design Mach number of 1.7. Euler simulations of three-dimensional biplane wings of several configurations were conducted. Because of the existence of wing tips, three-dimensional biplane wings do not perform as well as two-dimensional biplane airfoils. This is because the areas affected by Mach cones originated from the wing tips, which precludes the occurrence of an appropriate pressure wave interaction. Thus, the wing tip area has a large drag coefficient. To overcome these problems, a tapered wing is herein considered. After parametric studies, a wing planform was determined, the taper ratio and aspect ratio of which were 0.25 and 5.12, respectively. Aerodynamic design of wing section shapes of the three-dimensional tapered biplane wing was conducted using an inverse-problem method. The designed biplane wing shows a better lift-to-drag ratio performance than the two-dimensional flat-plate airfoil in the range where the lift coefficient is more than 0.17. Tapered wings were also found to have several span sections that achieve better performances than two-dimensional biplane airfoils.

Aerodynamic Design of Three-dimensional Low Wave-drag Biplanes Using Inverse Problem Method

The Busemann biplane is a representative airfoil which has possibility of realizing lowboom and low-drag. Aerodynamic designs based on the Busemann biplane are demanded for future supersonic transports. In this paper, extension of the Busemann biplane airfoil to 3-D wing is firstly investigated. Then an inverse problem method is applied to designing a high L/D biplane wing after the evaluation of a capability of the method for designing a practical 3-D supersonic biplane wing. Analyses and designs are based on Computational Fluid Dynamics (CFD). Free stream Mach number is 1.7. The authors achieved the following performance. At 0.11 of CL, L/D of a tapered wing combined with rectangular root region having span sections of Busemann biplane is 16.9, and L/D of the inversely designed biplane is 19.7. In order to improve three dimensional demerits about aerodynamic performance such as Mach cones, we attempted whether a 3-D biplane wing, the upper element of which was a flat plate wing, converged at a known target wing. Finally, L/D of the biplane wing was improved to 20.0 by setting up target pressure distributions aiming at a reduction of CD due to Mach cones around the wing root or kink.

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...