Effect of Convective Schemes on LES of Fuel Spray by Use of KIVALES 2008-01-0930

In this study, a numerical experiment using a 2D convective equation and LES of an evaporative diesel spray for different convective schemes has been performed to examine effects of convective schemes on a fuel-air mixture formation of the diesel spray simulation and to determine the convective scheme used in KIVALES. In addition to KIVALES original schemes, such as QSOU, PDC and IDC, CIP was incorporated into KIVALES in order to calculate the convective terms with low numerical diffusion. The numerical experiment using the 2D convective equation showed that the numerical diffusion of CIP scheme was lowest in the convective schemes used in present study. However CIP scheme used was not a monotone scheme completely due to the overshoot and the undershoot of the scalar provided near the boundary. Hence, CIP scheme was employed for only the convective term of the LES momentum equation, while the other convective schemes were calculated using QSOU, which is a monotone scheme. The LES spray simulation showed that the sensitivity for convective schemes was significant high in the diesel spray simulation with LES approach. QSOU and PDC were unable to predict the unsteady behavior of the diesel spray, since the numerical dissipation is significant high to suppress the development of the vortex structure. On the other hand, IDC provided the unsteady behavior of the diesel spray, while an excessive turbulent vortex and an unphysical temperature rise near the spray periphery were simulated due to the numerical oscillation. CIP scheme showed that an unsteady motion of the diesel spray can be predicted with no unphysical temperature rise at the spray periphery.