United States Office of Naval Research (University Laboratory Initiative Grant No N00014-06-1-0445)

A spin on cavity formation during water entry of hydrophobic and hydrophilic spheres

A fully 3D simulation of fluid-structure interaction with dynamic wetting and contact angle hysteresis

Cavitation is a complex multiphase flow phenomenon with an abrupt transient phase change between the liquid and the vapor, including multiscale vortical motions. The transient cavitation dynamics is closely associated with the evolution of the cavitation vortex structures. The present paper investigates the cavitation vortex dynamics using different vortex identification methods, including the vorticity method, the Q criterion method, the Omega method (Ω), the λ2 method and the Rortex method. The Q criterion is an eigenvalue-based criterion, and in the Omega method, the parameter is normalized, is independent of the threshold value and in most conditions Ω=0.52. The Rortex method is based on an eigenvector-based criterion. Numerical simulations are conducted using the implemented compressible cavitation solver in the open source software OpenFOAM for the sheet/cloud cavitating flows around a NACA66 (mod) hydrofoil fixed at α=6°, σ=1.25 and Re=7.96×105. The flow is characterized by the alternate interactions of the re-entrant flow and the collapse induced shock wave. Results include the vapor structures and the vortex dynamics in the unsteady sheet/cloud cavitating flows, with emphasis on the vortex structures in the cavitation region, the cavity interface, the cavity closure, the cavity wakes, and the foil wakes with the shedding cavity. The comparisons of the various methods, including that the vorticity method, the Q criterion method, the Omega method, the λ2 method and the Rortex method, show the performances of different methods in identifying the cavitation vortex structures. Generally, during the attached cavity growth stage, the Q criteria can well predict the vortex structures in the cavitation region and at the foil trailing edge in the pure liquid region, while with the Omega method and the Rortex method, the vortex structures outside the attached cavity and on the foil pressure side can also be predicted. The λ2 method can well predict the vortex structures in the cavity closure region. During the re-entrant jet development stage, the vortex structures in the re-entrant jet region is weak. During the cavity cloud shedding stage, the vortex dynamics at the foil leading edge covered by newly grown cavity sheet is different from that during the attached cavity sheet growth stage. During the shock wave formation and propagation stage, strong vortex structures with both the size and the strength are observed owing to the cavity cloud shedding and collapse behavior. The influence of the small parameter e in the Omega method on the cavitation vortex identification is discussed.

Cavitation vortex dynamics of unsteady sheet/cloud cavitating flows with shock wave using different vortex identification methods

Data-driven modal decomposition of transient cavitating flow

Numerical study on strong nonlinear interactions between spark-generated underwater explosion bubbles and a free surface

Numerical investigation of the water entry of a hydrophobic sphere with spin

Effects of air injection on the characteristics of unsteady sheet/cloud cavitation shedding in the convergent-divergent channel

The influence of ventilated cavitation on vortex shedding behind a bluff body

Physical and numerical study on unsteady shedding behaviors of ventilated partial cavitating flow around an axisymmetric body

Unsteady behavior of ventilated cavitating flows around an axisymmetric body

Decai Kong

Papers

Numerical investigation of the water entry of a hydrophobic sphere with spin

Effects of air injection on the characteristics of unsteady sheet/cloud cavitation shedding in the convergent-divergent channel

The influence of ventilated cavitation on vortex shedding behind a bluff body

Physical and numerical study on unsteady shedding behaviors of ventilated partial cavitating flow around an axisymmetric body

Unsteady behavior of ventilated cavitating flows around an axisymmetric body