| Neil Pryde RS:X windsurfing is one of the most important sailing events in the Olympic Games,world championships and so on.It is also an advantageous sport in China.China’s sports researchers have been engaged in the scientific research of the sailing board project for a long time.The scientific research helps the Olympic Games,which enables the Chinese sailing board athletes to control the ship(board)and sail wing of the sailing board at a higher level under different competition environments,and improves the overall competitive level of the sailing board project in China.However,our country’s windsurfers lack the ability to pump the sail under the condition of small wind,which often makes the competition fall short.In order to increase the knowledge of sailboard athletes about the aerodynamic characteristics of the sails when they are pumping the sails,and then to improve the level of the technology of the sails,this study takes the women RS:X sails as the research object,Using Computational Fluid Dynamic method,by solving the Reynolds averaged Navier Stokes equations and establishing the evaluation method for the propulsive performance of the sails.In this paper,the aerodynamic characteristics of the sails are studied when the sails are pumping in the direction of the chord in the upwind course and the sails are pumping in the direction of the mast in the downwind course.Based on the rules of avoidance and a series of numerical calculation results in the windsurfing competition,this paper analyzes the actual situation of the application of the upwind and downwind courses in the individual and team competition,and puts forward a scheme of selecting the combination of the frequency and amplitude of the sail with excellent propulsion performance.First of all,the geometric numerical model of the sail wing is established based on the actual situation of the sailboard project.Through the comprehensive investigation of the video of the sailboard competition and the actual training in the Olympic Games and the world championships,the angle of attack and the range of wind speed of the sail wing are analyzed,and the way of shaking the sail wing is determined to be that the sail wing pumps around the chord direction in the upwind course and the sail wing pumps around the mast direction in the downwindward course.By using User Defined Function to load the motion equation to control the amplitude and frequency of the sail,the lift coefficient and drag coefficient are determined to be the aerodynamic performance evaluation indexes of the sails,and the thrust coefficient along the actual course angle direction of the sails is the propulsion performance evaluation indexes of the sails.Secondly,in order to verify the reliability of the numerical simulation method and discuss the grid independence of the computational domain,the wind tunnel experiment of the aerodynamic characteristics of the sail wing model is carried out.The experimental conditions are as follows:the wind speed is 5 m/s,6 m/s and 7 m/s,the attack angle is 0°,-10°,-15° and20°,the sail frequency is 0.60Hz,1.00Hz and 1.50Hz,and the sail amplitude is 23.8° and 27.1°.It is found that the boundary layer grid y+=10 is not as accurate as y+=1,but the error is less than 15%compared with the experimental value.The boundary layer grid y+=10 can greatly save the computational resources of the numerical simulation of the sail.By comparing the numerical simulation results with the experimental results under different turbulence models,it is determined that the calculation accuracy of Realizable k-ε equation and SST k-ω two turbulence models are suitable for the numerical simulation of the sails.Then,according to the situation of the upwind course,the aerodynamic performance of the sails with different angles of attack(5°,10°,15 °,20°,25°,30°,35°,40°,45°)and different wind speeds(2m/s,3m/s,5m/s,7m/s,9m/s,11m/s)is simulated,and the angle of attack of the sail is 200 and the speed is 3m/s.The aerodynamic performance of the sail wing in different amplitude(2°,4°,6°,8°,10°),different frequency(0.67Hz,1.00Hz,1.3 Hz,1.67 Hz,2.00Hz)is simulated.Compared with other sail of different frequencies and amplitudes,the lift characteristics of the sails can be improved to a certain extent,and the lifting effect is related to the frequencies and amplitudes;the mean value of lift coefficient of the sails is higher when the sails of different frequencies and amplitudes are chosen to pumping in a large range at low frequencies,while the proper amplitude at high frequencies is in a better lift characteristics of the sails;in terms of the propulsive performance of the sails,the propulsive performance of low-frequency matching with large amplitude is better;when the frequency is 1.30Hz,1.67Hz,2.00Hz and the amplitude is 8°,the mean value of the thrust coefficient is the largest,which indicates that the high-frequency matching needs to select the appropriate amplitude to obtain better propulsive effect,and the smaller the same amplitude frequency is,the lower the energy consumption is.At the same time,the aerodynamic performance of the sail wing in the downwind course is simulated in different amplitude(3°,6°,9°,12°,15°)and different frequency(0.50Hz,0.67Hz,0.83Hz,1.00Hz,1.17Hz)at the attack angle of 90° and the wind speed of 2m/s.Not all the sails in the downwind course have the promotion effect on the sailboard.When the frequency is 0.50Hz and the amplitude is less than 12°,the frequency is 0.67Hz and the amplitude is less than 7°,the frequency is 0.83Hz and the amplitude is less than 4°,the propulsion effect is lower than the sliding state.Therefore,try to avoid low amplitude and low frequency when sailing downwind;when choosing large amplitude sailing,it needs to cooperate with appropriate frequency to provide better propulsion effect,and the best propulsion effect is when the frequency of sailing is 1.17Hz and the amplitude is 9°.Finally,based on the rules of avoidance and a series of numerical simulation results in the windsurfing competition,this paper analyzes the situation of upwind and downwind sailing,and puts forward the scheme of selecting the combination of frequency and amplitude of the excellent propulsion performance,predicting the possible avoidance to speed up the sailing,reducing the possibility of the athletes to avoid the waiting events;combined with the analysis of energy consumption and sail propulsion performance,this paper proposes the matching selection of the amplitude and frequency of the sail in the upwind and downwind segments,and analyzes the matching scheme of the frequency and amplitude of the sail in the upwind and downwind segments according to the body shape and physical quality of the athletes.Based on the aerodynamic characteristics of the sailwing in upwind and downwind courses with different amplitude and frequency obtained by numerical simulation,the selection and matching of the frequency and amplitude of the sails are determined,which can promote the coaches and athletes to understand the characteristics and propulsion effect of the sailboard in a more scientific and comprehensive way.The comprehensive improvement of the control ability of the sails and wings lays a foundation for the athletes to improve their skills and tactics so as to achieve excellent results in the competition. |
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