Research On Characteristics Of Flow Field And Propulsion Of Underwater Dual Synthetic Jets

Active flow control is one of the hot research areas in aviation and fluid dynamics.Based on the chaotic theory and non-liner system theory,the dual synthetic jets technology as a new active flow control technology was proposed by Luo zhenbing from National University of Defense technology about 10 years ago.The dual synthetic jets technology soon became a newly-developing method to solve problems from active flow control area,and is attracting more and more researchers' attention.The unique flow-field characteristics of the dual synthetic jets(DSJ)and the working attributes of the DSJ actuators make the technology suitable for a large class of applications,and that also make it become one of the most promising international research fields.As the key part of DSJ technology,dual synthetic jets actuator(DSJA)not only has the property of the existing synthetic jets actuator(SJA),but also has the superiority of high energy efficiency,compact structure,easy miniaturization and strong environment adaptation.Because of the many advantages of DSJA,it has been gradually applied to the small underwater vehicle.And with the marine excavation becoming a new hot trend,the advent of remote operated underwater vehicle(ROV)and automated underwater vehicle(AUV)has provided an application platform for DSJA.Now only a few developed countries are exploring and investigating the underwater dual synthetic jets(UDSJ)technology,and many problems about mechanism and applications need further study.The UDSJ technology is fresh in our country,it is important to expand the study of the UDSJ technology and make it into productivity,both in theory and engineering.By numerical and experimental methods and techniques,the formation and operation principles and characteristics of UDSJ,as well as the feasibility to apply UDSJ to propulsion of AUV are studied in this thesis.First of all,this paper summarized the background and research status of the application of UDSJ to underwater vehicles in chapter one.Then,through numerical simulation,the flow mechanism and flow characteristics of UDSJ are discussed,which will provide a reference and foundation for the experimental research.Chapter three is the key chapter of this paper,which contained the main experimental methods and techniques,as well as the main conclusions.In this chapter,experimental investigation on unsteady flow field structure of UDSJ is carried out with particle image velocimetry(PIV)measurement technique.The experimental results of both instantaneous and average flow fields show the formation of UDSJ and characteristics of the unsteady flow field,reveal the symmetry of average flow field created by underwater dual synthetic jets actuator(UDSJA).This chapter also compares the characteristics of different flow field when the parameters,such as orifice distance,orifice depth,orifice diameter,orifice shape and frequency,amplitude,waveform of forcing voltage,which will be helpful for the design,optimization and application of the UDSJ.The propulsion characteristics of UDSJ are investigated using propulsion measuring system in chapter four.The influence of working parameters on propulsion is studied by changing the driving frequency,amplitude of voltage and voltage waveform.The results shows that there is an optimum driving frequency which can make the propulsion reach the maximum value and that the propulsion would rise when the amplitude of voltage rise.Finally,the last chapter reviews and summarizes the whole thesis,give out the main conclusions and innovation points,indicates the research trends for the next step's work.