A study on the early stage of a transitional boundary layer and far field noise using a large eddy simulation technique

Flow characteristics are numerically investigated when a packet of waves consisting of a Tollmien-Schlichting wave and a pair of Squire waves evolves in a flat-plate laminar boundary layer using a large eddy simulation with a dynamic subgrid-scale model. Characteristics of early stage transitional boundary layer flow such as the .LAMBDA. vortex, variation of the skin friction and backscatter are predicted. Smagorinsky constants and the eddy viscosity obtained from the dynamic subgrid-scale model significantly change as the flow evolves. Far Field noise radiated from the transitional boundary layer shows the dipole and quadrupole characteristics owing to the wall shear stress and the Reynolds stresses, respectively.