Drag reduction of airplane fuselages through shaping by the inverse method

The axial singularity solution for the axisymmetric inverse problem has been extended to utilize doublet elements with linear intensity distribution. The solution converges faster than the source-based method, and is therefore quite promising. A procedure based on this solution has been used to design low-drag laminar fuselage shapes for small aircraft applications with a volumetric Reynolds number range of 10-30 million. A profile with a fineness ratio of 6, transition at 40% of body length, and volumetric drag coefficient of 0.012 at a nominal Rqq of 15 million, has been developed. The present inverse procedure was shown to be a powerful alternative to optimization methods. Several transition criteria were investigated in the course of the study. The Crabtree criterion appears to be the most consistent. Experimental transition data for axisymmetric bodies at high (flight) Reynolds numbers are urgently needed.King Saud Universit