Effect of Angles of Attack on the Hydrodynamic Forces of Manta Ray

摘要

The numerical investigation of the passive hydrodynamic performancernof the manta ray beneath the water surface is presented. The main aimrnis to investigate the effect of attack angle on hydrodynamic forces ofrnthe manta ray near the water’s surface. Three dimensionalrnincompressible Navier-Stokes equations are resolved with RNG k-εrnturbulence closure model. The undulation of the free surface is capturedrnby the volume of fluid (VOF) method. Numerical simulations arerncarried out with the manta ray oriented with the longitudinal axis atrnattack angles of -5, -2.5, 0, +2.5 and +5 degrees with various swimmingrnspeeds ranging from 0.5m/s to 4.5m/s. The drag coefficient and the liftrncoefficient of the manta ray are measured and compared. Results showrnobvious differences between negative and positive angles of attack.rnAdditionally, the deformation of the free surface induced by the glidingrnmanta ray is also captured and compared.