Comparative analysis of effectiveness of new formulas for averaged-velocity distribution in longitudinally uniform turbulent flows

Abstract

A new five-layer model of the structure of longitudinally uniform turbulent flows in which the flow is divided into a near-wall layer and turbulent core is substantiated in [1] on the basis of disclosures made in [5]. The near-wall layer is divided into a layer with negative turbulent velocity, and two layers with a positive increasing (more rapidly at first, and then more slowly) turbulent viscosity. The turbulent core is partitioned into zones in which the turbulent viscosity is linearly dependent on the distance from the wall, and then maintains its own constant value; this corresponds to zones with logarithmic and parabolic averaged-velocity distribution. In contrast to existing models, the boundaries of these layers are considered moveable and dependent on Reynolds number and relative equivalent roughness. The distribution of turbulent velocity along the normal to the wall is considered universal, and is defined by the parameters a and A. The first parameter a is related to the thickness aw of the near-wall layer: w a v u * . (1) The second parameter A is related to the position a A of the interface of the curve of the averaged-velocity distribution in the turbulent core in the logarithmic and parabolic sections: