Numerical and particle image velocimetry characterizations of flow structures under steady state condition

A combined numerical and experimental study has been carried out to examine the structure of the flow field from a 4 valve cylinder head under steady state conditions. In this paper, Particle Image Velocimetry (PIV) and the finite-volume Computational Fluid Dynamic (CFD) package, STAR CCM+ have been used on a single cylinder Lotus engine head with a pent-roof for a number of fixed valve lifts at two pressure drops of 250 mm and 635 mm of H₂O, equivalent to engine speeds of 2,500 and 4,000 RPM respectively. The Reynolds Stress Turbulence Model (RSTM) is used to simulate the turbulent flow structure. The generated mesh is a polyhedral type that holds nearly 3.7 million grid points. The computational results were validated through qualitative and quantitative comparisons with the PIV experimental measurements on both horizontal and vertical cross sections. Results show reasonable agreements between numerical and experimental outcomes for the mean and RMS velocity values at different locations inside the engine cylinder. The nature of the flow structure, together with discussions on the discrepancies observed are presented and discussed.