Elements of Gas Dynamics

Review and prospect of supersonic business jet design

Supersonic biplane—A review

This paper addresses the aerodynamic performance of Busemann type supersonic biplane at off-design conditions. An adjoint based optimization technique is used to optimize the aerodynamic shape of the biplane to reduce the wave drag at a series of Mach numbers ranging from 1.1 to 1.7, at both acceleration and deceleration conditions. The optimized biplane airfoils dramatically reduces the effects of the choked flow and flow-hysteresis phenomena, while maintaining a certain degree of favorable shockwave interaction effects at the design Mach number. Compared to a diamond shaped single airfoil of the same total thickness, the wave drag of our optimized biplane is lower at almost all Mach numbers, and is significantly lower at the design Mach number.

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Adjoint based aerodynamic optimization of supersonic biplane airfoils

The lift-type vertical axis wind turbine (Darrieus rotor) is considered to be a promising device for harnessing wind energy due to its potential advantages. Traditionally, a standard Darrieus rotor has a single ring of airfoils (two or three airfoils) that spins about a vertical axis and has low starting torque. A few researchers have stated that the Darrieus rotor with two sets of blades is likely to improve not only the starting ability but also the power coefficient. However, they have not provided sufficient evidence to support their statement. Thus, in this paper, we conducted a detailed computational fluid dynamics (CFD) investigation on the characteristics (e.g., power output, static torque, vortex, and pressure contours) of this rotor with two sets of blades. The effect of the distance between the outer and inner blades on the performance of this rotor was also discussed and quantified. The findings of this paper are expected to help in developing this new type of Darrieus rotor and offer valuable...

A detailed investigation of a novel vertical axis Darrieus wind rotor with two sets of blades

A Fundamental Study for the Development of Boomless Supersonic Transport Aircraft

Supersonic biplanes can possibly achieve low-boom and low-drag supersonic flights. In the present study, aerodynamic analysis and design of two-dimensional (2-D) biplanes were investigated with the help of computational fluid dynamics (CFD) tools. By utilizing an inverse-design method, a 2-D biplane configuration with lower wave drag than the single flat-plate airfoil at sufficient lift conditions (C
 l > 0.14) was designed at its design Mach number (M
 ∞ = 1.7). In general, although, supersonic biplanes show superior aerodynamic characteristics at their design Mach numbers, unfortunately, they are characterized by poor performances under their off-design conditions. Flow choking occurs at high subsonic speeds, and continues to Mach numbers greater than the design Mach number in the acceleration stage due to flow hysteresis. Hinged slats and flaps were applied as high-lift devices to avoid the flow choking and concomitant hysteresis problems, and were also used as actual high-lift devices under take-off and landing conditions. As further improvement, morphing and Fowler motion were considered. Finally, a series of 2-D biplane configurations from take-off (and landing) to cruise conditions were studied by applying the slats and flaps, as well as morphing mechanisms, to our inversely designed biplane.

Aerodynamic characteristics of a two-dimensional supersonic biplane, covering its take-off to cruise conditions

§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

A Study of Busemann-type Biplane for Avoiding Choked Flow

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.

Kazuhiro Kusunose

Papers

Supersonic biplane—A review

A Fundamental Study for the Development of Boomless Supersonic Transport Aircraft

Aerodynamic characteristics of a two-dimensional supersonic biplane, covering its take-off to cruise conditions

A Study of Busemann-type Biplane for Avoiding Choked Flow

Aerodynamic Design of Biplane Airfoils for Low Wave Drag Supersonic Flight