Simulation Of The Flow Around Combined Columns And Analysis Of Hydrodynamic Interference

The hoistable mast is an important communication equipment on the underwater vehicle.With the development of photoelectric and image technology,in order to improve its hydrodynamic performance and conform to the miniaturization development trend,the shape of the mast are gradually developed into the complex combined column.The combined cylinders are usually connected vertically by different regular cylinders,such as airfoil cylinders whose tail was cut off.When this combined mast is extended out of the underwater vehicle,the surrounding flow field will cause complex disturbances and affect its performance due to its special structural shape.Therefore,it is necessary to calculate and analyze the flow around the combined mast in different flow field,which is also important to improve the stealth performance of underwater vehicle.Based on the comparison of turbulence model and free surface description method in CFD,the RNG k-? turbulence model and VOF method are used to simulate the airfoil around the free surface.The calculated results matche well with the experimental results of the hydrodynamic laboratory of the University of Iowa.The accuracy of the method is verified and the method is carried out in the follow-up work.Based on the study of the flow around the airfoil,the numerical calculation of the flow around the unmanned flow field and the free liquid flow field is carried out,a numerical study is made on the flow around the combined column in the unbounded flow field and the free-surface flow field.The The hydrodynamic coefficient of the column is analyzed and the flow field characteristics are obtained.The fluid velocity gradient at the interface of the combined column is very complicated and the flow is very complicated.The free liquid has a great influence on the vortex and the hydrodynamic characteristics,and the water surface fluctuates obviously,and the hydrodynamic coefficient of the column is more random.Finally,the variation law between the hydrodynamic characteristics of the column and the angle of attack and arrangement is calculated and analyzed.The results show that with the increase of the angle of attack,the force of the column is obviously increased,and the flow separation position moves toward the head,and the phenomenon of the Carmen vortex in the wake flow field is obvious.In the tandem arrangement,the shielding effect of the combined column at the upstream makes the force of the cylinder at the downstream level decrease,and the wake in the flow field tends to be steady.In the parallel arrangement,the lift and drag coefficient of the cylinder is greatly increased.The fluid is only separated in the tail of the combined column,and the farther away from the combined cylinder,the stronger the mutual interference between the trails,and the flow field shows obvious three-dimensional characteristics.