Attachment Line Transition in Supersonic Flow

Abstract

According to a criterion proposed by Poll, leading edge contamination by a turbulent boundary layer occurs when a characteristic Reynolds number (R) over bar{*} exceeds a critical threshold. Two series of experiments have been performed in order to assess the validity of this criterion. The first one was carried out on a swept cylinder at Mach 3. In the second series of experiments, a swept wing was designed with a leading edge providing values of (R) over bar{*} close to the flight values of the inner wing of a supersonic transport aircraft at Mach 2. Both experiments indicated that the leading edge flow became turbulent for values of (R) over bar{*} in rough agreement with Poll's criterion. Additional experiments were performed in order to investigate the effects of roughness elements placed on and off the attachment line.