NUMERICAL STUDY OF BYPASS TRANSITION

A large-eddy simulation has been performed of a flat-plate boundary layer undergoing transition to turbulence under free-stream turbulence at a level of 6%. The properties of the simulated transition match those found experimentally: not only is the position and length of transition in agreement with available data, but the mechanism of transition also appears to correspond closely, since disturbances seen in the laminar layer prior to transition are found in the simulation. Statistical data have been gathered that allow the computation of all terms in the derived equations for the Reynolds stresses at four x stations. Aspects of these balances are presented that allow new insights into the physical mechanisms at work. The importance of the wall-normal component of free-stream turbulence and the timing of the redistribution of energy into this component through the fluctuating pressure field are revealed. (C) 1995 American Institute of Physics.