Form Optimization Of Sonar Fairing

Modern middle and large naval ships usually install the integrated sonar detection device in the bottom of the bow and uses sonar fairing which acoustic signal can passing through and has good acoustics feather surface to protect this device. The sonar fairing can increase sonar noise-signal ratio and enhances the general performance. Because the bulbous sonar fairing extrudes on the bow, when the ship navigates in the sea, fluid passing though this kind of appendage will produce turbulent boundary layer, the liquid particle in the turbulent boundary layer makes fluctuation pressure and this pressure will induces radiation noise directly. This radiation noise will increases the background noise and decreases the sonar noise-signal ratio. Because of sonar fairing, it is inevitable to produce some fluid noise, but in some navigation speed, the value of fluid noise depends on the scale and hull line of sonar fairing. The aim of this thesis is to reduce the fluid noise and develop the fluid noise numerical algorithm by CFD and form optimization of sonar fairing.First of all, this thesis uses uniform designing method to research the model of sonar fairing.And then, research the fluid noise numerical algorithm basing on the CFD technology, analyze the result of numerical method and compare with experiment. After affirming the validity of numerical result, use regression analysis method to find the relation function between the fluid noise power level and influence factors of fairing form.Finally, develop the sonar fairing form research of optimization basing on genetic algorithms, and check the application value of this method to design and evaluate the low noise appendage form through analyzing numerical optimization result and comparing with model experiment result. After validating the result, it is found that the method in this thesis can be used to optimize the form of sonar fairing and makes great effect in forecasting and directing. fluid noise of sonar fairing. Comparing with the old model, the maximal noise power level on the surface of the new model reduces 3.7dB,so the optimization result is satisfied...