Structures of a viscous-wave flow around a large-diameter circular cylinder

An analysis of the phenomenon of diffraction of viscous (water) waves caused by a large-diameter, surface-piercing vertical circular cylinder is performed. The three-dimensional time-dependent Navier-Stokes equations in primitive variables (velocity-pressure formulation) are considered for numerical simulation of the given wave case, and (for the first time at the best of the authors' knowledge) an approach followed is that of the Direct Numerical Simulation (DNS), with no models being used in the calculations for the fluctuating portion of the velocity field. The results obtained in terms of the wave runup and in-line force are compared with those given by the close-form velocity-potential solution for the same wave case and, with those given by the numerical integration of the primitive-variable Euler equations, as well as with data of experimental nature obtained by other authors. For further investigation of the flow fields, the swirling-strength criterion for flow-structure extraction is applied to the computed velocity fields, so unveiling a complex configuration of the viscous-flow structures in the vicinity of the cylinder external wall.