SIMULTANEOUS INFLUENCE OF TURBULENCE INTENSITY AND SCALE ON BY-PASS LAMINAR-TURBULENT TRANSITION

This paper presents the results of experimental correlations for transition inception, taking the influence of both intensity and the scale of external turbulence into account. The momentum thickness of a boundary layer was used to make the turbulence scale non-dimensional. Two new parameters, ITu and Ilu, evaluated as integrals taken from the leading edge of the plate to the start of the transition were used to express the averaged values of the intensity and scale of turbulence. A new experimental correlation for the point of transition inception, Re**, was calculated as a product of these two new parameters raised to the power determined in the process of three-dimensional regression. The measurements of local skin friction coefficient C-f and the intermittency factor., as a Weibull cumulative distribution function made it possible to determine the transition region. These new results were compared with ones known from literature.