An Aerodynamic Design Method for Supersonic Natural Laminar Flow Aircraft

The computation of boundary-layer properties and laminar-to-turbulent transition location is a complex problem generally not undertaken in the context of aircraft design. Yet this is just what must be done if an aircraft designer is to exploit the advantages of laminar flow while making the proper trade-offs between inviscid drag, structural weight and skin friction. To facilitate this process, a new tool is developed. This thesis presents a designoriented method for the aerodynamic analysis of supersonic wings including approximate means for estimating transition and total drag. The method consists of a boundary-layer solver combined with a fast and robust transition scheme based on the well-known en criterion. The boundary-layer analyses employed are computationally inexpensive but sufficiently accurate to provide guidance for advanced design studies and to be incorporated in multidisciplinary design optimization. The boundary-layer solver is based on an enhanced quasi-3D sweep/taper theory which is shown to agree well with three-dimensional Navier-Stokes results. The transition calculation scheme is implemented within the boundary-layer solver and automatically triggers a turbulence model at the predicted transition front. The laminar instability amplification values used in the en criterion are based on algebraic fits to linear stability results for streamwise and crossflow modes. This parametric transition prediction method compares favorably with exact linear theory on relevant geometries and successfully computes transition for a supersonic flight test. Integration of the present design method with numerical optimization is discussed, and airfoil section and wing/body shape optimizations are performed. Wing/body drag minimization studies suggest that low-sweep supersonic aircraft with extensive laminar flow may have a significant drag advantage over conventional designs.