Hydrodynamic Research Of The Effect Of Combined Jets On The Flow Around The Circular Cylinder

Cylindrical structures are commonly used in practical applications in marine engineering,such as structures such as lower pontoons of ocean platform,tower rods,columns of floating wind turbines and so on.When the incoming-flow Reynolds number is high,the Karman vortex street will appear in the wake of the cylinder,which will cause the cylinder to experience periodic changes in lift and drag.Especially when the vortex emission frequency is close to the natural frequency of the structure,the structure will have a strong resonance phenomenon,resulting in large The lateral and in-line vibration of the amplitude,which is called vortex-induced vibration(VIV),has a serious impact on the safety of the structure.Therefore,the method of suppressing wake vortex has become a hot spot in academic research.In this paper,the starting point is to reduce the lift resistance of the cylinder,and study the effect of the combined jet arrangement and the rate of fire on the shape of the wake vortex and the lift drag coefficient of the flow around the cylinder.From the perspective of wake vortex control,the VIV phenomenon of the cylinder is suppressed and reduced Its impact on structural safety.Since the strong convection caused by the jet poses a challenge to the calculation accuracy and efficiency of the turbulence model,this paper compares the accuracy and efficiency of the four sub-grid models of Smagorinsky,ILES,LDKSGS and OF-LDKSGS to calculate the flow around a cylinder.According to the results,the ILES with both accuracy and efficiency was selected as the sub-grid model for subsequent simulations.At the same time,the impact of the ILES model on reducing the diameter of the calculation domain while keeping the near-wall grid unchanged was further evaluated,ensuring the reliability and feasibility of the research..The jet on the front stagnation was classified into several forms based on the average flow filed around the front stagnation point,and the influence on the drag and lift coefficients and the circumferential pressure coefficients were investigated during the different forms of the jet on the front stagnation point.Furthermore,the fact that the position of the sub-jets determines the function of combined jets was interpreted through the principal orthogonal decomposition and the analysis of pressure filed near the wall.The consequence indicates a balance that when sub-jet angle?_J=150°,namely sub-jets near the stagnation point after,sub-jets can vortex shedding directly,making the fluctuating wake vortex fractured and broken,which inhibits the coefficients of drag and lift effectively,however,if the injection ratio is too high,they incur a larger amount of fluctuating vortex and affect the suppression of the drag and lift.Finally,through the optimization analysis and design of the non-dimensional jet velocity of the combined jet,the optimal lift-drag suppression configuration scheme of the combined jet is obtained:Under the conditions?_J=150°,when Re=3.9×10~3,the ratio of jet velocity is 0.125;whenRe=2×10~4,the one is 0.25.