Research On Drag Reduction Performance Of Passive And Active Deformation Of Flexible Wall

Marine transportation plays an important role in the development of world trade.The energy consumption of ships due to fluid resistance cannot be ignored.As human beings pay more and more attention to energy conservation and environmental protection,the study of turbulence drag reduction has become a top priority.The design and research of turbulence drag reduction methods using certain biological characteristics of marine organisms has become a trend.Scientists found that the flexible skin of marine organisms such as dolphins can change the shape of their skin surface in real time according to changes in their surrounding flow field conditions,so that they can reduce the fluid resistance and increase the flow rate.Inspired by this concept,this paper research on the drag reduction performance of the passive deformation and active deformation of the flexible walls.In this paper,the flexible flat plate and the rigid flat plate are used as the drag reduction comparison.The Workbench is used to simulate the flexible wall drag reduction,and the calculation module for simulating the bidirectional fluid-solid coupling is established.The SST k-? turbulence model is selected.In order to calculate the drag reduction effect in different flow velocity,the simulated flow velocity range is divided into three groups: low speed(1m/s-3m/s),medium speed(10m/s-15ms),and high speed(18m/s-22m/s).The results were postprocessed in CFD-POST and then analyzed for drag reduction mechanism.The simulation results show that in the three speed groups,the flexible plate has a certain drag reduction effect,and the overall drag reduction effect shows an increasing trend with the increase of the flow rate;When the flow velocity reaches 19m/s,the drag reduction effect begins to gradually decrease.The drag reduction mechanism of the flexible wall can be summarized as the passive deformation generated by the fluid load acts as a buffer absorption.According to the differential pressure method,a simple circulating water tank experimental platform was built,and the polyurethane test pieces were compared with the structural steel test pieces.Five sets of experiments were carried out.The experimental results show that the flexible test pieces used in this paper have a certain drag reduction effect in the experimental flow velocity range(0m/s-5m/s),and the drag reduction rate shows a law of increasing with the increase of flow velocity.The simulation of wall active deformation was carried out in the Fluent,a control algorithm for the active wall deformation using the wall normal speed as the input signal is designed,and the UDF program is written in Fluent accordingly.The Realizable k-? turbulence model was selected and the simulated drag reduction research was carried out in the flow range of 10m/s-15m/s.The simulation results show that the active deformation control scheme has achieved a certain drag reduction effect in the designed flow velocity range,the drag reduction effect shows a trend of increasing first and then decreasing as the flow rate increases.The drag reduction mechanism of the active deformation wall scheme can be summarized as the vortex generated by the low velocity fluid retained in the deformation plane acts to block the high speed fluid.