Experimental Assessment of Reynolds-Averaged Dissipation Modeling in Engine Flows

The influence of the constant C₃, which multiplies the mean flow divergence term in the model equation for the turbulent kinetic energy dissipation, is examined in a motored diesel engine for three different swirl ratios and three different spatial locations. Predicted temporal histories of turbulence energy and its dissipation are compared with experimentally-derived estimates. A “best-fit” value of C₃ = 1.75, with an approximate uncertainty of ±0.3 is found to minimize the error between the model predictions and the experiments.

Using this best-fit value, model length scale behavior corresponds well with that of measured velocity-correlation integral scales during compression. During expansion, the model scale grows too rapidly. Restriction of the model assessment to the expansion stroke suggests that C₃ = 0.9 is more appropriate during this period.