The present study treats with the onset of shear layer vortex in a jet diffusion flame and its development. The flow instability of jet depends on the density variation in the combustion field, i.e., heat release and different fuels etc. We perform a direct numerical simulation for two fuels, i.e., CH4 and C3H8 in the Reynolds number of 500 to 3000 based on the exit of fuel injection tube with a diameter of 10mm. The density of C3H8 is larger than that of air, but the density of CH4 is smaller. The flame sheet model of infinite chemical reaction and unity Lewis number are assumed in the simulation. It is found that intermittent shear layer vortex region occurs before periodic vortex region and that the intermittent region for C3H8 appears at a lower Reynolds number than that for CH4. In the periodic vortex region, the vortex for C3H8 changes from outward to inward rotation in the downstream zone of fuel jet, unlike the case of CH4. The vortex frequency is represented in terms of Strouhal number, almost independent of the Reynolds number. Furthermore, the effect of thermal buoyancy outside the flame is examined. It is revealed that a large scale vortex induced by thermal buoyancy enhances the onset of shear layer vortex and maintains the development of periodic vortex.
宮本直樹 , 吾郷弘 , 久井守 , 渡辺隆治 , 水野高志
In this paper, a microscopic simulation of traffic flow on a traffic signal network is developed. Its purpose is to apply to evaluation of signal control and various traffic operations such as right-turning lane. In this simulation, the speed and location of individual vehicle are renewed every short time period. Detailed behaviors of each vehicle such as deceleration and stoppage at red signal, departure and acceleration at green signal and car-following are reproduced. Turning traffic at signalized intersections and lane-change to adjacent lane or to right-turning lane are taken into consideration. It was found that it is possible to reproduce traffic situation on 4-lane streets of about 10 km length at the same computation speed as real time by using personal computer, and that it is possible to evaluate signal control and right-turning lane.