Calculation of the turbulent flow in plane diffusers

Abstract

Purpose

To provide an analysis of turbulent flow in plane diffusers for graduate and postgraduate students (researchers) which can help them to understand turbulent flows and turbulence modelling.

Design/methodology/approach

Steady, incompressible, turbulent flow in two‐dimensional plane diffusers, where Reynolds averaged Navier‐Stokes (RANS) equations were simplified using the theory of turbulent boundary layers in integral form adjusted for the internal flow. To close the RANS equations, the mixing length model proposed by Michel et al., which was previously used for the calculation of turbulent flow in a straight channel with a uniform cross section, is applied for the calculation of the turbulent flow in plane diffusers. Also, in this paper, the velocity profile is approximated in every cross‐section of the diffuser by a six‐order polynomial, whose coefficients depend upon the three form parameters. Using this transformation, the system of governing equations was reduced to the three ordinary differential equations which were solved numerically.

Findings

A comparison between results obtained (velocity profiles) and experimental data obtained using HWA and LDA shows very good agreement. The method of integral equations of boundary layer is a relatively old method and tends to be forgotten since more advanced methods have been introduced. However, the results obtained using this method for the calculation of turbulent flow in a plane diffuser show a very good agreement with experimental data. Therefore, in engineering applications when simplicity and low‐cpu times are required, the integral method can still be applied successfully.

Originality/value

This paper offers practical help to an individual starting his/her research in the computational fluid dynamics (turbulence modelling).

Citation

Vujičić, M.R. and Crnojević, C. (2007), "Calculation of the turbulent flow in plane diffusers", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 17 No. 5, pp. 533-547. https://doi.org/10.1108/09615530710752991