The complex hydrodynamics of water entry by a spinning sphere are investigated experimentally for low Froude numbers. Standard billiard balls are shot down at the free surface with controlled spin around one horizontal axis. High-speed digital video sequences reveal unique hydrodynamic phenomena which vary with spin rate and impact velocity. As anticipated, the spinning motion induces a lift fo...

In the paper, air cavity created by vertical water entry of cylinders with different slenderness ratio (defined as “s=L/D”) is investigated experimentally, theoretically, and computationally. The study focused on range Froude numbers, Fr = V /( gr ) 0.5, (12< Fr< 30). Particular attention given to effect ratios surface seal time, evolution process cavities. To understand physical processe...

The perturbations existing on a breaking wavefront can be potential explanation for the slamming pressure variability in wave impacts. Here, we investigate effect of these by forced vertical two-dimensional circular cylinder with constant downward velocity standing waves. Through experimental modelling and numerical simulation, force is measured several amplitudes wavelengths. phase tuned such ...

The motion characteristics of trans-media vehicles during the water-entry process were explored in this study in an effort to obtain the optimal water-entry condition of the vehicle for developing a novel, single control strategy integrating underwater non-control and in-air control. A water-entry dynamics model is established by combining the water-entry motion characteristics of the vehicle i...

In this paper a denoising strategy based on the EEMD (Ensemble Empirical Mode Decomposition) is used to reduce background noise in non-stationary signals, which represent forces measured scaled model testing of emergency water landing aircraft, generally referred as ditching. Ditching tests are performed at constant horizontal speed 12 m/s and vertical velocity beginning impact 0.45 m/s. The da...

this article is going to criticize both theories of forcefully entry, and of kindly entry, of islam into qum. three points will be proved through this article: a) arab triumph in qum was difficult and qumian people resisted muslims, but this does not mean that islam entrance to qum was by force and violence ; b) in addition to knowledge and comprehension factor, there were social, economical an...

BACKGROUND The water entry of a submersible aircraft, which is transient, highly coupled, and nonlinear, is complicated. After analyzing the mechanics of this process, the change rate of every variable is considered. A dynamic model is build and employed to study vehicle attitude and overturn phenomenon during water entry. Experiments are carried out and a method to organize experiment data is ...

The water-entry problem is a complex multiphase hydrodynamic that directly related to many engineering applications and natural phenomena, such as torpedo airdrops, seaplane landings, ship slamming. Therefore, studying the influence of microscopic properties object surface on macroscopic phenomenon during water entry necessary. In this study, volume fluid model continuum force models are couple...