Low-drag airfoils for transonic flow of dense gases

Abstract.

Low-drag airfoils for transonic flow of BZT gases are constructed through a nonlinear small-disturbance theory on this topic. This kind of transonic flow is characterized by the high nonlinearity of the fluid thermodynamic behavior that is closely coupled with its compressible flow dynamics. Utilizing BZT gases may result in low drag exerted on airfoils operating at high transonic speeds. This advantage may be further improved by a proper design of the airfoils' shape. The modified airfoils are characterized by arcs along which the flow is sonic and that connect to a sharp tail. These airfoils may give the highest free stream Mach number for which the flow is nowhere supersonic. Using an analysis in the hodograph (velocity) plane, an analytical formula is derived to describe the sonic arc. Numerical computations using the Euler equations demonstrate that the modified airfoils have significantly lower pressure drag against standard airfoils and their critical Mach number is increased to higher values.