Hydrodynamic Performance Analysis Of The Mini-underwater Vehicle And Interaction Between Two Bodies

By the virtue of its own characteristics such as small volume, light weight and goodmaneuverability, Mini-Underwater Vehicle has a promising future in ocean science research,and has been paid more and more attention. Mini-Underwater Vehicle will conduct six-degreeof freedom motion when working in complex marine environment, and will in the complexflow field perturbed by the carrying platform during release and recovery process. It is easilyinterfered by irregular wave, current and vortex because of propulsive and control systempower limited. How to adapt to the complex marine environment and control the navigationand work status are the problems Mini-Underwater Vehicle must face. To solve theseproblems, it is necessary to understand the hydrodynamic performance of Mini-UnderwaterVehicle in complex flow field, including motion response to irregular wave, current andvortex, and then establish the control strategies. So the hydrodynamic performance ofMini-Underwater Vehicle in complex flow field is the basis to solve these problems. Thispaper was based on the CFD technique to study the hydrodynamic performance of differenttypes of Mini-Underwater Vehicle in uneven flow field, and conducted experiment on theirhydrodynamic performance in complex flow field. The interaction between two bodies suchas plate and bluff body, propulsive performance of twin flapping wing and tandem wing werealso researched. The main content of this paper included:(1) The steady and unsteady hydrodynamic performance of Mini-Underwater Vehicle inuniform flow with the revolved body and flat body were predicted by the CFD technique;associated hydrodynamic coefficients were obtained and compared with experimentresults. The influence of turbulence model, grid quantity and parallel calculationefficiency were analyzed. Based on these calculations, the user defined functions werewritten to achieve uneven flow fields with linear velocity distribution, and thehydrodynamic performance of the revolved body and flat body conducted the straightmoving, oblique moving and six-degree freedom motion were numerically calculated inthese uneven flow field.(2) The experiments of hydrodynamic performance of Mini-Underwater Vehicle in complexflow field were conducted in Harbin Engineering University basin. The three dimensional complex flow fields were generated by underwater pump; the flow wascirculated in the basin. The three dimensional velocities were measured by Dopplercurrent profiler. The velocity distribution of complex flow fields generated by differentpump frequency and quantity were compared. The influence of complex flow field onthe hydrodynamic performance including longitudinal force, lateral force and yawingmoment of the revolved body and flat body versus velocity distribution and drift anglewere measured by the three component balance, and the experiment results were alsocompared with the CFD calculation results.(3) Based on the unstructure mesh, refined the mesh in boundary layer, and transition ofdifferent scale mesh were achieved by Non-Conformal grid algorithm; the lift, drag andpitching moment performance were calculated when the distance between theMini-Underwater Vehicle and the large underwater carrier was changed.(4) The fluid dynamic performance interaction between bluff body (circular cylinder, squarecylinder) and upstream and downstream plate were calculated based on the structuremesh. The flow interference phenomenon between bluff body and plate were researchedbased on the force of bluff body and flow parameter variety before and after plate placed.(5) The dynamic mesh and sliding mesh methods were adopt to calculated the propulsiveperformance of twin flapping wing and tandem wing, the influence of velocity, phase lag,flapping frequency and amplitude on propulsive performance were discussed. Theadvantages of twin flapping wing and tandem flapping wing on thrust and thrustefficiency than single flapping wing were analyzed systematically. Lift performance oftwo-and three-dimensional flapping plate were calculated by dynamic mesh method. Theinfluence of flapping parameters to lift coefficients of two-and three-dimensional wereanalyzed; and the grid quantity and time step sensitive test were conducted.