The Research On Flow-induced Vibration And Acoustic Characteristics Of Liquid Filled Wing-shaped Elastic Cavity

Treated as one of the three major noise sources of submarines, the fluid-noise played keyrole on the noise stealth characteristic, and methods on its reduction attracted wide interests.Meanwhile, the fluid-noise also makes influence on noise distribution in the cavity. In thisessay, a simulation method dealing with fluid-noise feature for fluid filled cavities has beenestablished, which can be utilized for assisting the designing and material optimization forenvelope shell of command cabinet of submarine and other underwater structures like shroud,and also provide consultation for the arrangement of acoustical equipments in the cavities.Our simulation process exploited the advantage of commercial FEM software ANSYS, theCFD solver FLUENT and acoustical FEM software ACTRAN to estimate the flow noisecharacteristic of elastic shell structure model. The main points of this essay are: firstly,envelope shell, side and bow model is established through ANSYS, the convergence of meshhas been checked meeting different demands of calculation; secondly, after comparison ofdifferent turbulence theory model, eddy viscosity model was chosen to calculate the kineticenergy and dissipation of turbulence, then the standard k εmodel of reynolds stress isobtained, the flow field of outer space of the structure model is calculated by FLUENTsoftware, which shows the mechanism and distribution of turbulence and wake flow, then thetransition area of flow velocity is discovered; finally, the turbulent pulsating pressure is usedas stimulation, and inner, outer noise radiation and vibration of the model is calculated by theACTRAN software. Meanwhile, Lighthill acoustical analogy method is introduced, we usethe velocity of flow field as sources, the perturbation of turbulence boundary layer and itsradiation noise is calculated. A fluid-noise solution with better accuracy is then obtained bycoupling the direct radiation noise on the boundary layer and flow exited vibrato noise. In afurther step, structures’ flow noise under various flow velocity excitation and multiplestructure thickness.The fluid-noise shows positive correlation with the flow velocity, and the flow-inducedvibration of envelope shell model is relatively strong, an increase of the shell thickness causesreduction of count of modals in this frequency range, and also the intensity of sound radiation.The in-chamber sound pressure is stronger than the outer. The turbulence intensity, pulsationpressure and noise radiation is relatively big on sharp areas of the model.Corresponding measure system has been built to prove the correctness of our simulationmethod, a air foil envelope shell model has been tested by gravitational water tunnel in laboratory of underwater acoustic technique. The experiment data fits the simulation solutionwell.