Investigation of the wall pressure, wall shear stress and velocity fields associated with a turbulent spot in a laminar boundary layer

The wall pressure field of artificially generated turbulent spots in a laminar boundary layer was investigated. Ensemble averages of the wall pressure signatures, in zero and favorable pressure gradients, show that the spot's pressure signature is characterized by two positive pressure peaks and a central negative pressure region along the centerline which evolves into one negative and one positive pressure perturbation in the wing tip region. For the zero pressure gradient, contours of the ensemble averaged wall pressure measured relative to the laminar value show that the spot produces a leading pressure excess followed by a pressure defect region having its maximum values at the spot's wing tips. The trailing edge consists of a spanwise region of pressure excess also having its maximum value at the wing tips.