Resistance Reduction Characteristics of the Deep-Sea Submersible Surfacing Based on Flexible Appendage
In order to solve the problem of long surfacing time of deep-sea manned submersible,a flexible appendage drag reduction method based on three-dimensional flow field is proposed,and hair strands are selected as the material of the flexible appendage,and a new type of flexible appendage is designed.The length of the flexible appendage with optimal drag reduction performance and the drag reduction effect under multi-attitude conditions are obtained by six-component sensor,and the lift power spectrum is obtained by Fourier transform.Particle image velocimetry is used to photograph the changes of the wake flow field before and after the addition of the flexible appendage to the submersible,and the vortex energy spectrum is obtained by Fourier transform,and proper orthogonal decomposition(POD)decomposition is performed on the flow field.The results show that the best drag reduction effect of the flexible appendage is 7.2％under the vertical surfacing condition,corresponding to a hairline length of 0.1 L(the length of the scaled-down model of the manned deep-sea submersible is L=22 cm),and the drag reduction effect ranges from 2.7％to 7.2％under each surfacing attitude condition.The maximum turbulence kinetic energy of the flow field in the bow section of the submersible is reduced by 15.8％,and that amidships is reduced by 14.5％,after the addition of flexible appendages;the vortex structure of the flow field becomes more complicated,with small and medium-sized vortices obviously increasing,and large vortices being dispersed.The vortex structure of the flow field becomes more complicated,with the number of small and medium-sized vortices obviously increases,the large vortex is dispersed,the asymmetry of the main mode flow field of POD is strengthened,and the disorder of the flow field increases.The research results can provide some references for the drag reduction method of flexible attachment in three-dimensional flow field.
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