Influence Of Shape And Structure Coupling Elements On The Drag Reduction Of Exhaust Pipe

The material of society is more and more abudance,people’s life improved day by day.The damand fors is also rising. The exhaust pollution, especially the smog pollution is alsocoming. The pollution is effecting our work, life and physical and mental health. Reducingthe drag of exhaust pipe can improve the efficiency of the engine exhaust. The exhaust ofharmful gasses can be reduced. Therefore, the drag reduction of exhaust pipe is veryimprovement. In previous studies, imitating shark skin swimsuits are producted by imitatingthe body structure of creature and melting the thought of bionomic coupled, it can reduce thedrag effective. However, in the techonolgy of biomimetic, the effect of different couplingelements are different. The article based of shape and structure coupling elememts, studingthe effect of shape and structure coupling elements on the drag reduction of exhaust pipe andexploring the mechanism of drag reduction. The main results indicate that:1、 The shape of groove, concave and elliposid units are based on the surface of shark,dolphin, dung beetle, predacious diving beetle, pigeon and the structure of elliptical,trapezoid, parabolic, semi elliptical, semi trapezoid, semi parabolic;2、 Appling the Fluent software to simulate the velocity, the wall shear stress, turbulenceintensity of the pipe inner side. Analysed the drag reduction preformance of the unit withdifferent shape, and the unit with with the same shape but different structure, and the unitwith the same shape and structure but different characteristic value;3、 In the shape coupling element, the groove shape unit has a better drag reductionpreformance, and in the structure coupling element, the groove shape unit with parabolicstructure has a better drag reduction preformance, through change the width and depth ofparabolic structure we found, width3mm and depth0.5mm unit has a better performance;4、 The influence mechanisms of drag reduction performance of exhaust pipe treated bybiomimetic coupled:(1) The groove shape chang the contact way of gas-solid from gas-solid to gas-solid andgas-gas, which can cut down the friction drag and the velocity of the fluid will buimproved;(2) The groove shape can increase the thickness of vicous sublayer of boundary layer,reduce the velocity gradient vertical the layer. The drag come from the layer isreduced; (3) The form of movement fluid in the exhaust pipe in turbulence and during the fluidflows, the turbulent will be happen. The groove shape can hinder the turbulentbursting and the turbulent intensity is reduced, as a result, the drag is decreased.