Parametric Study on the Free-Fall Water Entry of a Sphere by Using the RANS Method

Pengyao Yu,Tianlin Wang,Chunbo Zhen,Cong Shen,Haoyun Tang

doi:10.3390/jmse7050122

Pengyao Yu, Tianlin Wang + Show 3 more

Open Access

https://doi.org/10.3390/jmse7050122

Copy DOI

Abstract

Motivated by the application of water-entry problems in the air-drop deployment of a spherical oceanographic measuring device, the free-fall water entry of a sphere was numerically investigated by using the transient Reynolds-averaged Navier–Stokes (RANS) method. A convergence study was carried out, which accounts for the mesh density and time-step independence. The present model was validated by the comparison of non-dimensional impact force with previous experimental and numerical results. Effects of parameters, such as impact velocity, radius, and mass of the sphere on the impact force and the acceleration of the sphere, are discussed. It is found that the peak value of the non-dimensional impact force is independent of the impact velocity and the radius of the sphere, while it depends on the mass of the sphere. By fitting the relationship between the peak value of the non-dimensional impact force and the non-dimensional mass, simplified formulas for the prediction of peak values of the impact force and the acceleration were achieved, which will be useful in the design of the spherical oceanographic measuring device.

Highlights

Compared with the slow release of oceanographic measuring devices in water, air-drop deployment from a ship or a helicopter is simpler and faster, especially in the deep sea
The free-fall water entry of a sphere was numerically investigated by using the transient
It was found that the non-dimensional impact force is independent of the impact velocity and the radius of the sphere

Summary

Introduction

Compared with the slow release of oceanographic measuring devices in water, air-drop deployment from a ship or a helicopter is simpler and faster, especially in the deep sea. Predicting the impact dynamics associated with water-entry problems is of fundamental importance in the design of oceanographic measuring devices which are deployed using air-drop. Korobkin presented a rational derivation of several analytical models, such as the classical Wagner model, the generalized Wagner model, and the Logvinovich model [3]. The accuracy of these models for the prediction of the hydrodynamic loads was compared and assessed by Tassin et al [4]

Objectives

Discussion

Conclusion