采用SIMPLE算法结合RNGk-ε湍流模式计算了全附体潜艇DARPA Suboff潜艇的三维流场,并对流场模拟结果进行验证,在此基础上加载FW-H声学模型(The Ffowcs Williams and Hawkings Model)进行非定常计算,对潜艇流噪声声场进行模拟,计算了潜艇的自噪声和辐射噪声,验证了两种潜艇流噪声声场的特性。计算结果表明所采用的计算方法可以比较准确地模拟潜艇的流场和流噪声。
分别采用RNG k-ε,Realizable k-ε,k-ω,SSTk-ω目前应用较广的四种湍流模型结合RANS方程和FW-H声学模型(The Ffowcs Williams and Hawkings Acoustic Model)对水滴型潜艇模型的流噪声进行模拟,并将计算结果分别与试验值进行了对比分析,从中我们知道对于本文的计算模型和条件,相比较于其他三个湍流模型RNGk-ε结合RANS方程和FW-H声学模型的方法可以较好的预报潜艇的阻力和流噪声。
In this paper,a numerical simulation of flow-induced noise by the low Mach number turbulent flow with a sinusoidal wavy wall was presented based on the unsteady incompressible Navier-Stokes equations and Lighthill's acoustic analogy.Large eddy simulation (LES) was used to investigate the space-time flow field and the Smagorinsky sub-grid scale (SGS) model was introduced for turbulence model.Using Lighthill's acoustics analogy,the flow field simulated by LES was taken as near-field sound sources and radiated sound from turbulent flow was computed by the Curle's integral formulation under the low Mach number approximation.Both spanwise wavy wall and streamwise wavy wall with various wall wave amplitudes were discussed to investigate their effects on reducing the drag and flow noise.The relationship between flow noise and drag on the wavy wall is also studied.
A source-to-far-field computation procedure aiming at predicting the noise generated by the underwater propeller was presented. Detached eddy simulation(DES) was used to resolve the unsteady flow field,which was taken as input data as noise propagation. Far-field sound radiation was performed by means of Ffowcs Williams-Hawkings(FW-H) equation. The computation procedure was finally applied to a typical marine propeller,David Taylor Model Basin(DTMB) 4118. The sound pressure and directivity patterns of this propeller were discussed.
Large eddy simulation (LES) was used to investigate the space-time field of the low Mach number, fully developed turbulent boundary layer on a smooth, rigid flat plate. The wall-pressure field simulated by LES was analyzed to obtain the pressure statistics, including the wall-pressure root-mean square, skewness and flatness factors, which show the wall pressure distribution was not Gaussian. The profile of the auto-power spectral density and the contour of the streamwise wavenumber-frequency spectral density of wall-pressure were plotted. The "convection ridge" can be observed clearly and the convection velocity can be calculated from the location of the convection peak.
