Research And Application Of Flow Characteristics Around A Cylinder With Bionic Non Smooth Surface

As a typical form of viscous fluid motion,flow around a body exist widely in nature world and engineering applications,such as flow over a wing,flow around a pier and flow around a ship.Because of the flow transition,flow separation,vortex and other complex flowing,which cause vibration and noise,the flow around a body has a great impact on engineering applications.In this paper,the problem caused by flow around a body is studied(chapter 1),and a grooved surface followed the bird feather is put forward based on the special surface of bird wings(chapter 2).The following researches are carried out:First,a numerical simulation method of flow around a cylinder based on star-CCM+ software was established,as the boundary layer transition,flow separation,surface vortex shedding will occur when flow past a cylinder,which can be used for reference(chapter 3).By using the bionic non-smooth surface,it is proved that grooved surface has the ability to disturb the flow in boundary layer,optimize the lift coefficient as well as drag coefficient,delay the flow separation based on the analysis of velocity,pressure,kinetic energy,vorticity and other indicators.The design concept and four main control parameters of the bionic grooved structure are determined,the basic theory for the application of this technology is also established(chapter 4).Secondly,because of the flow separation and the stall of wing when flow past a wing with large thickness at high angle of attack,the flow control technology using bionic grooved surface is applied.The response surface model with the average drag coefficient and the average lift coefficient as the response output is established respectively.The significance of four main control parameters on the target is verified by ANOVA,the sensitivity ordering and the interaction between each two parameters are studied,which provides a reference for the engineering applications of bionic non-smooth surface.Finally,taking lift coefficient and drag coefficient as indexes,an improved NSGA-II genetic algorithm was put forward by adding the crossover operator based on response surface test analysis and the multistage mutation operator.The optimal parameter combination of bionic non smooth surface on naca0024 airfoil at high angle of attack is obtained.The simulation results show the optimization of lift and drag coefficient as well as the delay of stall angle of attack,which proved the feasible of application of bionic grooved surface and the reliability of optimization method.