Hydrodynamics numerical investigation of hoistable masts for underwater vehicles

Using the unsteady incompressible Navier-Stokes equation as the governing equation, the large eddy simulation (LES) model is implemented to investigate the shedding of vortices, the flow pattern of turbulence, the unsteady pressure fluctuation and the time history of the lift coefficient and drag coefficient of hoistable masts with various mast shapes and various arrangements in this paper.Combining the FFT, combined time-frequency transform and wavelet power spectrum analysis, the characteristics of unsteady pressure can be obtained in both time and frequency domain.It shows that the main frequency of pressure fluctuation is near the frequency of vortex shedding in time domain using the FFT method.It can be inferred from the combined time-frequency transform that the unsteady pressure fluctuation has obviously the peak value and the second peak value in time domain.It could indicate that the fluctuation power varies from the fluctuation frequency through the power spectrum analysis.By the data analysis, it shows that the vortex shedding is the dominant cause of the periodically pressure fluctuation.And the interaction pattern of wake and interplay between wake and the walls of masts under different arrangements are also discussed in this paper.