Numerical Simulation Of Drag Reduction Performance Of Bionic Shield Scale Skin Based On Immersed Boundary Method

With the deepening of human understanding of nature,bionic surface drag reduction technology has gradually become a research hotspot in the field of fluid drag reduction.Bionic shark shield scale is widely used on the surface of aircraft,ships and other equipment because of its excellent drag reduction performance.Considering the similarity between hydrodynamic excitation and multi-dimensional vibration excitation when Stewart mechanism works,a bionic shield scale skin structure is constructed by combining the miniaturized Stewart mechanism with bionic shield scale to reduce the resistance on the surface of underwater vehicle,and its drag reduction performance is studied based on the immersed boundary method.This paper mainly focuses on the following aspects:(1)The structural design of the bionic shield scale skin is completed.Based on the excellent drag reduction characteristics of the bionic shield scale,a new bionic shield scale skin structure is constructed by combining it with the miniaturized Stewart mechanism and arranging it according to the tile covering type.The key structural parameters of the bionic shield scale and the miniaturized Stewart mechanism are determined to ensure the multidimensional motion characteristics of the skin.In the mechanism dynamic analysis The skin dynamic model is established in ADAMS,and the relevant constraints and turbulence excitation are applied.Taking the vibration level drop as the evaluation index,the vibration isolation performance of the skin under different outrigger structural parameters is analyzed.(2)According to the large deformation characteristics of the skin fluid structure coupling interface,the fluid structure coupling control equation of the skin is established by the immersion boundary method to numerically simulate its drag reduction characteristics.In order to ensure the accuracy and stability of the numerical calculation results,the penalty parameter method is selected to deal with the immersed boundary quality problem The appropriate penalty parameters are determined by the interval step size.Based on the penalty parameter method,the space and time discretization of the fluid structure coupling governing equation is carried out,and the feasibility and accuracy of the numerical calculation method are verified by an example.(3)The discrete model of the bionic shield scale skin is established and the numerical solver is customized.The discrete model of the skin and the corresponding flow field domain are constructed in ibamr,and the adaptive refinement of the local mesh in the fluid domain is completed according to Berger rigoustsos clustering algorithm.The penalty parameter method is embedded into the main program,the resistance calculation program is written,and the relevant parameters of the solver are set The user-defined numerical solver is established,and the makefile file is compiled to compile the user-defined numerical solver,so as to realize the directional output of the calculated skin surface fluid resistance.(4)The effects of structural parameters and Reynolds number on the drag reduction performance of skin are analyzed.The effects of the elastic modulus of the bionic shield scale surface,the support stiffness and damping coefficient of the legs of the micro Stewart mechanism,the distribution spacing of the skin elements,and the mass and centroid height of the upper platform on the drag reduction performance of the skin are analyzed,and then the structural parameters of the skin are optimized.The influence of Reynolds number on the drag reduction performance of skin after structural parameter optimization is analyzed under different working conditions.It is found that the relative drag reduction rate of skin increases first and then decreases with the increase of Reynolds number,and the maximum drag reduction rate can reach 15.78%.