A Numerical Study Of Local Boundary Layer Receptivity To A Vortical Disturbance In The Freestream

Method of direct numerical simulation was used for the investigation of the local receptivity of a 2-D boundary layer of a flat plate to a harmonic vortical disturbance in the freestream. Under the interaction of the vortical disturbance and the local roughness element, T-S waves was detected in the boundary layer, thus confirming that a wavelength conversion mechanism and local receptivity existed. Relations between the receptivity and the length and height of the roughness element has been found, in agreement with the experimental observations. When the length of the roughness element was less than the wavelength of the T-S waves, the receptivity increased with it. On the other hand, when the length of the roughness element was larger then the wavelength of the T-S waves, the receptivity decreased with it. Thus, the strongest receptivity happened when the length of the roughness element was the same as the wavelength of the T-S waves.The receptivity increased linearly with the roughness height until it reached a value of 0.17 ( is the thickness of boundary layer).