| In order to improve the overall national strength of the country,it is imperative to vigorously develop the marine economy and national defense,and the marine vehicle plays an extremely important role in this development strategy.Reducing the fluid resistance in the course of motion can effectively increase the speed of navigation and improve the efficiency of energy utilization.The development of the world is closely linked to energy,and the solution to the energy crisis is the basis for sustainable development.Therefore,the technology of drag reduction has become a hot spot in the field of marine science and technology at home and abroad.This paper mainly studies on the rheological properties of puffer surface mucus and its application in drag reduction.According to the characteristics of migratory puffer,to study on the rheological properties of puffer epidermal characteristics and surface mucus,to construct the puffer skin tensile constitutive model and the Carreau model of puffer surface mucus in steady shear.Through simulation experiments,to study the influence of velocity,viscosity and wall roughness on the experiment,to analyse the drag reduction characteristics of puffer surface mucus.The specific research contents are as follows :(1)Use the method of sampling and measurement to study the distribution of puffer epidermal spur.Use Attension Theta optical contact angle measuring instrument to study the contact angle of Fugu epidermis and the factors affecting the contact angle.Use the CTM2100 microcomputer controlled electronic universal testing machine to study the tensile properties of the puffer epidermis and determine its tensile constitutive model.(2)Use the coaxial cylinder measuring system of MCR92 advanced rotating rheometer to test the rheological behavior of the mucus on the body surface of the puffer puffer and obtain the rheological properties of the mucus on the body surface of the puffer.The main factors influencing the experiment are: time laziness,concentration,scanning frequency,temperature and shear history.(3)By comparing other drag reducing agents or biological mucus,and combining with the needs of subsequent simulation experiments,the rheological properties of the body surface mucus of the puffer were analyzed.The Carreau-Yasuda model was used to fit the data and the mechanism of the viscosity reduction of the body surface mucus of the puffer was analyzed.(4)Use the method of numerical simulation to study the influence of velocity,viscosity and wall roughness on simulation experiment.Select the appropriate numerical simulation method,turbulence model,wall treatment method,control equation discretization method,discrete format,numerical solution of flow field,and initial simulation conditions.(5)In the case of smooth plane,water is used as a reference to calculate drag reduction rate.It is found that the drag reduction rate of mucus relative to water medium can reach 60%~70% and the smaller the velocity is,the higher the drag reduction rate is.It is found by simulation experiments that drag reduction performance of different concentration of mucus is almost the same.In the case of fluid medium,the non smooth surface of the skin spur of the puffer puffer was simulated and the smooth surface was taken as the reference,and the drag reduction rate of the non smooth surface was 1.68%~8.08%.(6)By analyzing the shear stress at the bottom of the region and calculating the velocity variation from the bottom to the top of the region,the bionic drag reduction mechanism of the rheological properties of the body surface of the puffer was as follows : the Mucus slows down the transition from laminar to turbulent flow,prolonging the interval of laminar flow and reducing velocity loss;the Mucus reduces the vibration of turbulent boundary layer,and accelerates the rate of change from Wall zero velocity to normal speed.So as to achieve the purpose of reducing the resistance. |
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