Analysis of Modal Growth on the Leeward Centerplane of the X-51 Vehicle

Abstract : A study of the transition behavior of the X-51 vehicle outer moldline has been made with particular emphasis on the leeward centerline of the vehicle. Based on encouraging earlier studies of first and second mode growth along the symmetry plane of other three-dimensional vehicle shapes, the focus of this work was to assess whether first or second mode growth is primarily responsible for transition along the leeward symmetry plane of the X-51. The authors selected several test cases from the database of available wind tunnel tests where measurements of the position of transition on the leeward side of the body were obtained. A grid of the three-dimensional forebody shape of the vehicle was generated, mean flow analysis completed for all test cases and the solution symmetry plane was extracted for each case to compute a planar and oblique modal disturbance analysis. For each case, the growth of the most unstable disturbances was assessed to determine if the cause of transition could be attributed to modal disturbance growth for any or all of these cases.