INFLUENCE OF THE PRESEPARATION FLOW STRUCTURE ON THE CHARACTERISTICS OF THE SEPARATION REGION BEHIND A BACKWARD-FACING STEP

This paper presents the results of investigations of the infl uence of the separated fl ow structure behind a rib located before the edge of the backward-facing step on the parameters of the separation region behind it. Numerical investigations were carried out by the method of large eddy similution in a plane air channel. The velocity of the developed turbulent fl ow at the inlet to the channel was assumed to be 25 m/s with a level of initial turbulence for three velocity components of 5%. The Reynolds number calculated by the initial velocity and the step height was 15,500. It has been shown that the creation of a preseparation region causes the two-dimensional fl ow to transform into a three-dimensional one before the edge of the back-facing step with the formation of nonuniform verticity along its length. This restructuring of the fl ow leads to an increase in the inhomogeneity of velocity parameters in the separated mixing layer. The fl ow expansion behind the step increased and was accompanied by local separation on the upper wall of the channel. The two separation regions caused a rapid growth of pulsations throughout the channel behind the step.
   
Author:  V. L. Zhdanov, D. A. Ivanov, Ya. I. Smul′skii, and V. I. Terekhov
Keywords:  plane channel, backward-facing step, rib, turbulent separation, separation structure
Page:  628