Mohammad Jalalisendi

Experiments on the water entry of asymmetric wedges using particle image velocimetry

In this work, we experimentally characterize the water entry of an asymmetric wedge into a quiescent fluid through particle image velocimetry (PIV). The wedge enters the water surface with an orthogonal velocity falling from a fixed height. We systematically vary the heel angle to elucidate the effect of asymmetric impact on the flow physics and on the fluid-structure interaction. The pressure field in the fluid is reconstructed from PIV data by integrating the Poisson equation. We find that the impact configuration significantly influences both the velocity and the pressure field, ultimately, regulating the hydrodynamic loading on the wedge. Specifically, as the heel angle increases, the location of maximum velocity of the flow moves from the pile-up region to the keel. At the same time, the pressure field significantly decreases in the vicinity of the keel, reaching values smaller than the atmospheric pressure. The spatiotemporal evolution of the hydrodynamic loading is thus controlled by the heel angle, with larger heel angles resulting into more rapid and sustained impacts.

A particle image velocimetry study of the flow physics generated by a thin lamina oscillating in a viscous fluid

In this paper, we study the flow physics produced by a thin rigid lamina oscillating in an otherwise quiescent viscous fluid. Particle image velocimetry (PIV) is used to extract the flow kinematics, which is, in turn, utilized to reconstruct the pressure distribution around the lamina through the integration of Navier-Stokes equations. The hydrodynamic loading experienced by the lamina is ultimately estimated from PIV data to investigate added mass and fluid damping phenomena. Experiments are conducted for varying Reynolds and Keulegan-Carpenter numbers to elucidate the relative weight of inertial, convective, and viscous phenomena on the resulting flow physics. In agreement with prior numerical studies, experimental results demonstrate that increasing the Reynolds and the Keulegan-Carpenter numbers results into the formation of coherent structures that are shed at the edges of the lamina and advected by the flow. This phenomenon is associated with nonlinearities in the hydrodynamic loading, whereby fluid...

A critical assessment of PIV-based pressure reconstruction in water-entry problems

Hull slamming constitutes an important class of impulsive loading for marine composites. In this work, we experimentally assess the effectiveness of particle image velocimetry (PIV) to resolve the flow physics and infer the pressure distribution in water entry problems. Toward this aim, PIV experiments are performed on a rigid wedge with a deadrise angle of 37 symmetrically impacting the water surface by free falling from a height of 50 cm. PIV measurements are systematically compared with data from an array of sensors, such as potentiometer, accelerometers, and pressure transducers. In the first part of our assessment, we compare the wedge entry depth and velocity obtained through PIV with the results obtained from the potentiometer and accelerometers. Next, we compare the reconstructed pressure and force from PIV with data from pressure transducers and accelerometers. Our results demonstrate the feasibility of PIV in the study of water entry problems, highlighting critical advantages of this non-invasive approach.