Simultaneous impact of intensity and tubrulence scale to a by-pass laminar-turbulent transition

Abstract

The influence of turbulence intensity on transition is quite well learned, especially for the zero pressure gradient. To characterize the main features of turbulence it is necessary to know its intensity but also its scale (most often the dissipation length is used as a length scale), usually related to a velocity along a streamline. In so far the investigation of the influence of turbulence scale is far away of completeness. In this paper the results of experimental correlations for the transition inception are presented with the use of two new parameters ITu and ILu that are created as integrals taken from the leading edge of the plate till the transition begins, expressing this way the averaged values of intensity and turbulence scale. The turbulence scale is made non-dimensional by the momentum thickness of a boundary layer. A new experimental correlation for the point of transition inception Re** is calculated in form of a product of these two new parameters raised to power determined in the three-dimensional regression procedure.