Numerical Prediction of Secondary Flows in Complex Areas Using Concept of Local Turbulent Reynolds Number

Abstract

A new model of turbulence is proposed for the estimation of Reynolds stresses in turbulent fully-developed flow in a wall-bounded straight channel of an arbitrary shape.

The main idea of a Multi-Scale Viscosity (MSV) model can be expressed in the following phenomenological rule: A local deformation of axial velocity can generate the turbulence with the intensity that keeps the value of the local turbulent Reynolds number below some critical one. Therefore, in MSV, the only empirical parameter is the critical Reynolds number.

Multi-scale viscosity has been verified on the pipe flow and applied to simulation of turbulence-driven secondary flow in elementary cell of the infinitive hexagonal rod array. Since MSV can predict turbulent viscosity anisotropy in directions normal and parallel to the wall, it is capable to calculate secondary flows in the cross-section of the rod bundle. Calculations have shown that maximal intensity of secondary flow is about 1% of the mean axial velocity for the low-Re flows (Re=8, 170), while for higher Reynolds number (Re=160, 100) the intensity of secondary flow is as negligible as 0.2%.

KEYWORDS:

• turbulence
• secondary flows
• hexagonal rod bundle