FLOW AND THERMAL STRUCTURES IN A TRANSITIONAL BOUNDARY-LAYER

A three-wire probe was specifically designed and fabricated to measure the flow structure and the thermal field in transitional and low Reyn olds number turbulent flow. In addition to the skin friction coefficie nt and Stanton number on the surface, detailed measurements were made of the mean and fluctuation quantities of the flow and temperature fie lds in the boundary layer. The evolution of the <(u upsilon)over bar> profiles indicates that turbulent shear is generated near Y+ = 70-100 and imposes itself on the wall within the boundary layer. <(ut)over ba r>, <(upsilon t)over bar>, epsilon(H), epsilon(M), and Pr-t were measu red near the end of transition and in the turbulent flow region. Pr-t is shown to be greater than the typical value of 0.9 in the near-wall region. The Reynolds analogy factor (2 St/C-f) in the early turbulent flow region is approximately 0.9, which is lower than the typical valu e of 1.2 for turbulent flow. The data presented in this paper serve as the baseline for a series of consecutive studies related to investiga ting various parameters that affect laminar-turbulent transition.