Research On Characteristics Of Air Drag Reduction Caused By The Variable Ovoid Non- Smooth Surface

With the rapid development of science and technology, the non-renewable resources such as oil, gas, coal on the earth increasingly decreased and the energy problem is becoming more and more serious. At present, solving the energy problem is related to human survival and development. The methods are mainly included as follows:(1) the developing of new energy; (2) improving the traditional energy utilization; (3) reducing the causes of energy dissipation. For the third method, it belongs to the new research field. In this field, the bionic non-smooth surface drag reduction theory provides a new thought and method.In this paper, inspired by the wave effect and desert terrain, the non-smooth structure of drag reduction is extracted by the numerical simulation, according to the theory of fluid dynamics, the characteristics research of non-smooth drag reduction is made to seek the best drag reduction unit structure. The inner mechanism of drag reduction is dug out to provide certain theoretical basis for engineering practice.Based on the bionics theory, this paper studied the bionic prototype and build the non-smooth structure size selection principle to extract the variation ovoid non-smooth structure mathematical model. The UG software was built to build a mutant ovoid structure prototype and non-smooth surface wind tunnel model. Secondly combining the reality of application situation, the numerical simulation system was set up by the simulation platform of ANSYS Workbench. The mesh of the model was divided by ANS YS Mesh module. The Realizable K-ε model was chosen to calculate when it was computed in Fluent as well as considering the wall effect. Finally it was conformed to meet the requirement of the test.In order to get different size and different characteristics of non-smooth structure, the orthogonal experiment method was chosen for the test design which was conducted under different condition of the actual working place. The parameters of velocity changed from low speed to high speed in 4m/s. The importance of each factor was studied by statistical methods. The order of drag reduction factor was listed as follow from high level to low level:the radius a, the longitudinal spacing d, half height h, half shaft 1. The best combination of optimum parameters was obtained by the analysis. Within the scope of the radius and the half high, the greater the value was the better drag reduction effect. And the longitudinal spacing between the intermediate value made minimum drag reduction rate. The half shaft in the middle of the test scope value made the best drag reduction effect.To further mine the drag reduction of the ovoid structure, one of the experiment result was selected. It was spread from the wall shear stress, turbulence statistics to velocity field. Each Angle was based on the actual analog data. Studies showed that non-smooth structure can change the turbulence characteristics of flow field and reduce the near wall turbulence intensity. The reverse flow was found within the ovoid structure. On the basis of the explore, the inclusion could be listed as follows:ovoid structure trigger quasi-ordered structure variation, non-smooth surface boundary layer thickness increases, ovoid structure variation with pressure joint effect.