Numerical Study On Unseparated Flow For Slender Axisymmetric Body

There would be large drag force for underwater vehicle with high speed. If noncavitation flow pattern can be realized, then it would greatly improve the drag-reduction characteristics for slender axisymmetirc body with high speed. The key step is to realize the unseparated flow pattern.Methods on how to gain the unseparated flow pattern is studied and numerical simulation is used to simulate the three methods: special body shape to control the zone with negative pressure gradient, turbolator ring, small ratio of slenderness. Great attention is firstly paid to analyze the effect of the length of zone with negative pressure gradient and the magnitude of negative pressure gradient on the flow separation. The feasibility of obtaining unseparated flow through the control of the length of the zone with negative pressure gradient is also researched. The body shape with special slope in the mid-section is crucial for the control of the negative pressure gradient zone. If shape slope changes steeply, then the length of negative pressure gradient zone is small and the magnitude of negative pressure gradient is great. So three slender axisymmetric bodies with special shape in the mid-section are simulated. Unseparated flow is realized when the shape slope is gentle. Body with turbulator ring or small ration of slenderness are examined and unseparated flow pattern is also realized.The simulation results show that the axisymmetric body with long length of negative pressure gradient zone and small magnitude of negative pressure gradient is advantageous to the unseparated flow. So new method on how to design slender axisymmetric body with unseparated flow pattern is put forward: design of body shape with flat negative pressure gradient. Axisymmetric body with that kind of pressure distribution in the mid-section and rear part is designed to testify the method. Numerical simulation shows that unseparated flow pattern is solved successfully.