Study on Fluidelastic Instability and Random Vibration of Tube Arrays
|Keywords||fluidelastic instability flow-induced vibration tube array heat exchanger|
The fluidelastic instable vibration and random vibration of tube arrays are studied in this dissertation. Its contents include:(1) Based on unsteady flow theory model, the program of calculating the critical velocity of fluidelastic instability is developed. And with the experiment data of H.Tanaka et al. , some examples are calculated and the results are discussed.(2) The detuning of the intrinsic frequency of tubes, the number of tubes in the calculation, axial-flow and the curvature of U-tubes, which influence on the critical velocity of tube arrays, are studied carefully.(3) The quasi-linear model using the frequency as the parameter is proposed to analyze the multiple-valued critical velocities and a method to calculate the intrinsic and excited critical velocities is given.(4) After some experiment data being analyzed, some hypotheses on the power spectrums of tube arrays are given in order to get the solution of responses of tubes excited by random forces of turbulence and vortex.(5) The influence of inactive supports on the critical velocity is discussed thoroughly, and after the relation between the critical velocity and vibration frequency is studied, a probabilistic method is put forward to estimate the expectancy of the critical velocity.(6) Numerical methods are used to take account of the influence on the critical velocity by disordered structures such as tube spans are changed due to manufacturing or assembling.Following are the two main computer programs developed : (1) to calculate the critical velocity, and (2) to calculate the responses of tubes. In these programs, modal analysis method are used to take account of the influences of non-uniform flow velocity distribution. And the single mode method or frequency truncation method is used to solve the problems when different modes are coupled with each other.