Freefall hydrodynamics of torpedo anchors through experimental and numerical analysis

In the present paper, the freefall hydrodynamic effects of torpedo anchors are studied through drop tests. A numerical computational fluid dynamics (CFD) model was used to simulate these drop tests relying on Reynolds-averaged-Navier-Stokes equations. A theoretical model hypothesis is necessary for these numerical simulations to define the inlet velocity, which was validated using physical experiments. The hypothesis uses the constant added-mass and drag coefficients, which are never constant in the field. Herein, the 1:50 scale model experiments (in a 4 m water pit) helped to capture the time-varying effect of the hydrodynamic forces (i.e., added mass and drag effects) of the dynamically installed torpedo anchors. In turn, the theoretical model is used in the numerical simulation of the CFD model to understand the hydrodynamic effects in the prototype. The parametric analyses are conducted with different anchor configurations as a part of the study. In particular, the effect of aspect ratio and anchor geometry (nose, fin configurations) are reported. Experimental findings report best hydrodynamic performance by the hemispheric nose followed by ellipse and ogive. In contrast, the conical nose shows inferior performance due to its significant lateral displacement. Numerical simulations also showed that long elongated cones (tip angle <60°) were more efficient.