Study On Drag Reduction Characteristics Of Cylindrical Flow Around V Groove Structure Surface

Jack-up platform pile leg structure is the core component of Jack-up platform and offshore structures.Its main function is to support the working platform above sea level to ensure its normal operation.In recent years,with the development of offshore oil and gas resources from the shallow sea to the deep sea,the length of the pile leg increases,the area acting on the pile leg also increases with the increase.In this environment,the circumfluence resistance becomes an important factor to ensure the safety of offshore platform.So,it is very important to control the flow resistance of offshore platform pile leg structure.Firstly,the Reynolds Criterion is used to simplify the structure of offshore platform pile leg structure,and the control variate method is used to analyze the drag coefficient,lift coefficient and strouhal number of different groove parameters.The results show that the groove depth has the greatest influence on the drag reduction effect around the cylinder.When the number of groove columns is 16 and the groove Angle is 60°,the drag reduction effect is the minimum when the groove depth is 0.035 D.The groove Angle has the greatest influence on the frequency of vortex shedding.As the increase of groove Angle,the drag coefficient decreases first and then increases,while with the increase of groove number,both drag coefficient and lift coefficient show a trend of decrease gradually.Secondly,the drag reduction mechanism of V-groove structure is studied by analyzing the lift coefficient,drag coefficient and lift power spectral density of the flow around a circular cylinder with different groove depths,and the distribution of velocity,pressure and vorticity in the wake field.The results show that the lift power spectral density and cylindrical flow strength increased as the increase of groove depth show a decrease trends.The wake vortex shedding also change with the increase of groove depth,more groove depth small the wake vortex,meanwhile,the energy of vortex carry decreases with the increase of groove depth;The groove structure can change the velocity distribution in the wake area,and with the increase of the groove depth,the wake velocity can recover the velocity more quickly.The groove structure can change the pressure on the front and rear edges of the cylinder.The groove structure can change the state of alternating vortex shedding,making the wake vortex more unstable.Finally,the velocity distribution nephogram of the rear flow field obtained under the experimental conditions is compared to verify the drag reduction performance of the surface of the V-groove structure.The correctness of the numerical simulation is verified by comparing the time-averaged velocity distribution map of the velocity at different sections of the test and simulation.Experimental study on the drag reduction effect of cylindrical flow around the surface of v-groove structure under different Reynolds number shows that the drag reduction effect of v-groove structure is more obvious when the Reynolds number is smaller.