Numerical Investigation On The Characteristics Of Aerodynamic Noise Induced By Flows Around Bluff Bodies

With the improvement of the qualit y of life,people have increasingly hig h requirements for the sound comfort on houses,offices,leisure places and other places like that,as well as public transport facilit ies.Equipments such as pantographs and landing gears,which are composed of simple bluff bodies,are indispensable components of high-speed trains and aircrafts respectively.However,the aerodynamic noise induced by flows around these equipments is extremely outstanding.Besides,in the field of civil engineering,with the rapid growth of populat ion,the lack of urban construction land and the development of construct ion technology,buildings are getting higher and higher,and the structures of which are becoming more and more complicated.As a result,the aerodynamic noise generated by these buildings becomes more obvious.Therefore,study on the aerodynamic noise of simple bluff bodies is the theoretical basis for reducing the overall aerodynamic noise of high-speed trains and aircrafts,and it also provides reference s for acoust ic environment design and aerodynamic noise control of buildings.In the present thesis,characterist ics of the aerodynamic noise of simple bluff bodies are studied in respect of sound generat ion,radiation and reception.And then,the simulat ion method of aerodynamic noise is applied to a super high-rise building to assess its indoor acoustic comfort,and reasonable recommendat ions on noise reduct ion are offered based on summary of the main results obtained from research on simple bluff bodies.The main contents in this thesis are shown in four aspects as followings:1.The advantages and disadvantages of several commonly used numerical methods to simulate flow field and acoust ic field,as well as their scopes of applicat ion,are assessed.And then,applicable numerical methods are clarified: the broadband noise sources model combined with the realizable k-? turbulence model is applied to simulate the near-field aerodynamic noise sources,and the unsteady SST k-? turbulence model and the acoustic analogy method based on the FW-H equat ion are applied to simulate the far-field aerodynamic noise.2.The near-field aerodynamic noise sources of bluff bodies are simulated,and the effects of oncoming wind speed,cross-sect ion and characterist ic size of bluff bodies on the magnitude and distribut ion of the aerodynamic noise source s are analyzed.Moreover,the relat ionship between the aerodynamic noise source s and flow-field parameters such as the turbulent kinet ic energy,turbulence dissipation rate and wall shear stress is discussed.Finally,a mathemat ical model is established to predict the surface acoustic power level,and to provide references for the low-noise-design of bluff bodies in pract ical applicat ions.3.The far-field aerodynamic noise radiated by bluff bodies is simulated,and the sound directivit y and sound attenuat ion are investigated.The effects of the flow speed,cross-sect ion and characterist ic size of bluff bodies on the magnitude,distribut ion and spectral characterist ics of the aerodynamic noise are analyzed.Besides,a mathemat ical model is established to predict the far-field aerodynamic noise.Finally,the relationship between the aerodynamic noise and aerodynamic forces are discussed,which provides references for noise reduction of bluff bodies in pract ical applicat ions.4.The numerical method of near-field aerodynamic noise sources is applied to a super high-rise building.Some flow-field parameters,which have principal effects on the magnitude and distribution of the aerodyna mic noise sources,are determined,based on the distribut ion of external flow field,pressure field and aerodynamic noise sources.The sound comfort in this building is assessed according to the environmental qualit y standard for noise,and then recommendat ions on noise reduct ion are put forward,based on the assessment results and the main invest igat ion results of the above simple bluff bodies.