Copyright © 2004 by the Kuwait Society of Engineers. All rights reserved. 1 Proceedings of IMEC2004 International Mechanical Engineering Conference December 5-8, 2004, Kuwait IMEC2004-FM050-CP TWO-DIMENSIONAL DIFFUSER SHAPE OPTIMIZATION Berge Djebedjian Mechanical Power Engineering Department, Faculty of Engineering, Mansoura University, El-Mansoura, Egypt E-Mail: bergedje@mans.edu.eg Abstract An approach for the optimization of turbulent flow in diffusers is presented. A methodology is developed to integrate a finite volume-based computational fluid dynamics (CFD) analysis and an optimization tool using micro-genetic algorithms (μ-GA). The CFD model is based on the Reynolds-averaged Navier-Stokes equations, with the standard k-ε closure turbulence model. This methodology is tested on the optimization through wall contouring of a given two- dimensional diffuser with a tailpipe discharge. Different area ratios are used in the study with a fixed diffuser length to inlet width ratio. The results indicate that the diffuser performance can be improved by this method. The improvement is marginal for small area ratios and increases substantially for great one. Keywords: Computational Fluid Dynamics (CFD), Genetic Algorithms, Optimization, 2-D Diffuser, Turbulent Flow Nomenclature AR area ratio, W 2 /W 1 for 2-D diffuser 1 ε C , 2 ε C constants in the k-ε model μ C eddy viscosity coefficient C p static pressure recovery coefficient F objective function I turbulence intensity, (%) k turbulent kinetic energy, (m 2 /s 2 ) L length of diffuser, (m) P turbulence energy generation rate, (m 2 /s 3 ) Ex p average static pressure at the diffuser exit, (Pa) In p average static pressure at the diffuser inlet, (Pa) Re Reynolds number, μ ρ / 1 W U In U mean streamwise velocity component, (m/s)