The free-surface impact of solid objects has been investigated for well over a century. This canonical problem is influenced by many physical parameters, including projectile geometry, material properties, fluid and parameters. Through advances in high-speed imaging visualization techniques, discoveries about the underlying physics have improved our understanding these phenomena. Improvements to analytical numerical models led critical insights into cavity formation, depth time pinch-off,...

Autonomous underwater vehicles (AUVs) are increasingly used for undersea exploration. The endurance of AUVs is limited by the onboard energy storage among which battery systems dominate. Various recharging methods employed to increase AUV range and autonomy. Currently, contact-based utilizes wet-mate connector technology that requires a high-precision docking, prone electrical safety issues. To overcome these limitations, wireless techniques have been explored in recent years. Wireless...

We present the results of a combined experimental and theoretical investigation vertical impact low-density spheres on water surface. Particular attention is given to characterizing sphere dynamics influence its deceleration shape resulting air cavity. A model developed which yields simple expressions for pinch-off time depth, as well volume entrained by sphere. Theoretical predictions compare favorably with our observations, allow us rationalize form water-entry cavities from buoyant nearly spheres.

The complex hydrodynamics of water entry by a spinning sphere are investigated experimentally for low Froude numbers. Standard billiard balls shot down at the free surface with controlled spin around one horizontal axis. High-speed digital video sequences reveal unique hydrodynamic phenomena which vary rate and impact velocity. As anticipated, motion induces lift force on thus causes significant curvature in trajectory object along its descent, similar to curveball pitch baseball. However,...

Abstract We present a study of the forces during free-surface water entry spheres varying masses, diameters, and surface treatments. Previous studies have shown that formation subsurface air cavity by falling sphere is conditional upon impact speed treatment. This focuses on experienced in both cavity-forming non-cavity-forming cases. Unsteady force estimates require accurate determination deceleration for high low mass ratios, especially as inertial hydrodynamic effects approach equality....

We present a study of the forces, velocities, and trajectories slender (length/diameter = 10) axisymmetric projectiles using an embedded inertial measurement unit (IMU). Three nose shapes (cone, ogive, flat) were used. Projectiles tested at vertical oblique impact angles with different surface treatments. The trajectory half-hydrophobic half-hydrophilc case impacting vertically was compared to symmetrically coated free angles. cases showed significantly more final lateral displacement than...

We present new observations from an experimental investigation of the classical problem crown splash and sealing phenomena observed during impact spheres onto quiescent liquid pools. In experiments, a 6 m tall vacuum chamber was used to provide required ambient conditions atmospheric pressure down $1/16\text{th}$ atmosphere, whilst high-speed videography exploited focus primarily on above-surface formation ensuing dynamics, paying particular attention moments just prior surface seal. doing...

We present a new method for resolving three-dimensional (3D) fluid velocity fields using technique called synthetic aperture particle image velocimetry (SAPIV). By fusing methods from the imaging community pertaining to light field with concepts that drive experimental mechanics, SAPIV overcomes many of inherent challenges 3D (3D PIV). This offers ability digitally refocus flow at arbitrary focal planes throughout volume. The viewable out-of-plane dimension (Z) can be on same order as...

It is well known that the water entry of a sphere causes cavity formation above critical impact velocity as function solid–liquid contact angle; Duez et al. ( Nat. Phys. , vol. 3 (3), 2007, pp. 180–183). Using rough with angle $120^{\circ }$ Aristoff & Bush J. Fluid Mech. 619, 2009, 45–78) showed there are four different shapes dependent on Bond and Weber numbers (i.e., quasistatic, shallow, deep surface). We experimentally alter number, number smooth spheres find two key additions to...

Striking the top of a liquid-filled bottle can shatter bottom. An intuitive interpretation this event might label an impulsive force as culprit in fracturing phenomenon. However, high-speed photography reveals formation and collapse tiny bubbles near bottom before fracture. This observation indicates that damaging phenomenon cavitation is at fault. Cavitation well known for causing damage various applications including pipes ship propellers, making accurate prediction onset vital several...

Abstract

It is known that the water entry of a body with recessed, cupped nose can suppress splash and air cavity typically observed for solid (Mathai, Govardhan & Arakeri, Appl. Phys. Lett. , vol. 106, 2015, 064101). However, interplay between captive gas in cup, quite subtle has not been thoroughly explored. Here we study dynamics associated vertical cups find variety regimes over range Weber numbers ( $We_D$ ) dimensionless cup depths. Our parameter space spans transition slow-developing...

Surface coating and impact velocity can dramatically affect cavity formation during water entry of spheres. Duez et al. [Nat. Phys. 3, 180 (2007)] present a theoretical limit, dependent on surface static wetting angle, below which air cavities no longer form. We show that transverse spin alters the spheres distribution to straddle this resulting in over half sphere none other half, yields similar results case dropped without spin, at same speed, when its is hydrophilic hydrophobic.

Obtaining pressure field data from particle image velocimetry (PIV) is an attractive technique in fluid dynamics due to its noninvasive nature. The application of this generally involves integrating the gradient or solving Poisson equation using a velocity measured with PIV. However, very little research has been done investigate error propagation PIV-based measurements calculation. Rather than measure through experiment, we by examining directly. We analytically quantify bound field, and...

We report results from an experimental study on the formation of stable–streamlined and helical cavity wakes following free-surface impact Leidenfrost spheres. Similar to observations Mansoor et al. ( J. Fluid Mech. , vol. 743, 2014, pp. 295–326), we show that acoustic ripples form along interface elongated cavities entrained in presence wall effects as soon primary pinch-off takes place. The crests these can act favourable points for closure, producing multiple pinch-offs, which are found...

Releasing a beach ball just under the surface of water will result in large and violent ``pop-up'' above surface. Contrary to intuition, increasing release depth sometimes results lower pop-up height. Experiments show that height is directly related depth, but correlation not always increasing. Particle image velocimetry reveals vortical structures shed during ascent nonvertical trajectories alter

Abstract A robust and intuitive understanding of fluid mechanics—the applied science motion—is foundational within many engineering disciplines, including aerospace, chemical, civil, mechanical, naval, ocean engineering. In‐depth knowledge mechanics is critical to safe economical design applications employed globally everyday, such as automobiles, aircraft, sea craft, meeting global 21st century challenges, developing renewable energy sources, providing access clean water, managing the...

The forces on an object impacting the water are extreme in early moments of entry and can cause structural damage to biological man-made bodies alike. These early-time arise largely from added mass, peaking when submergence is much less than one body length. We experimentally investigate a means reducing impact rigid sphere by placing inside jet so that strikes quiescent surface prior into pool. accelerates pool liquid forms cavity which falls. Through on-board accelerometer measurements...

Traditionally, the cavitation threshold is defined by some combination of vapor pressure and surface tension. However, these formulations present a large discrepancy with experimental data for cases where induced acoustic waves. The study aims to identify more suitable such cases. method adopted in this work consists visualizations high-speed camera direct measurements using hydrophone. collected confirmed that not proper indicator occurrence an system characterized high frequencies. main...

Quasiperiodicity, a partially synchronous state that precedes the onset of forced synchronization in hydrodynamic systems, exhibits distinct geometrical patterns based on specific route to lock-in. In this study, we explore these dynamic behaviors using recurrence quantification analysis. Focusing self-excited system-a low-density jet subjected external acoustic forcing at varying frequencies and amplitudes. We generate plots from unsteady velocity time traces. These provide insight into...

Ultrasound driven cavitation is widely used to intensify lab and industrial-scale processes. Various studies experiments demonstrate that the acoustic energy, dissipated through bubbles collapse, leads intense physicochemical effects in processed liquid. A better understanding of these phenomena crucial for optimization ultrasonic reactors, their scale-up. In current literature, visual characterization reactor reactivity mainly carried out with sonoluminescence sonochemiluminescence. These...

Samaras are known for their elegant and robust autorotation, a resilience that persists in the adverse conditions imposed by high-speed raindrops. Like flying insects, samaras descending from tall trees likely to be struck raindrops an intense storm. In this study, we detail collision dynamics impact regions across samara body drop-shedding mechanisms exhibit return autorotation. Impacts can pitch up 60 degrees and, some cases, induce spanwise roll. Raindrops may shatter or remain intact...