Numerical Investigation of Piston Speed in a Water Analog Engine on Transition to Turbulence for Experimental Modelling 2001-01-3604

A computational investigation of engine flow in an optical water analog engine has been carried out using KIVA. Three cases (20 RPM, 40 RPM and 60 RPM) are examined and discussed. From the comparison of the three different cases, there are obvious cyclic variations for different piston velocities. The discrepancies in the cases demonstrate that the transition to turbulence occurs at the lower RPM (e.g. 20 RPM) while fully developed turbulence seems to start at the higher RPMs (e.g. 40 and 60 RPM). These, therefore, suggest that 2D PIV used in previous measurement is valid at lower RPM because the measurement actually measures the jet or the turbulence transition from jet, but 3D stereoscopic PIV is certainly better and necessary at higher RPM due to the 3D character of the turbulence. The work will assist in the design of new experiments, and provide direction for improving modelling techniques.