Impact Force Measurement of a Spherical Body Dropping onto a Water Surface from Different Heights

Ryosuke Araki,Akihiro Takita,Edwin Carcasona,Tsuneaki Ishima,Yusaku Fujii

doi:10.12792/icisip2014.016

Abstract

The impact force of spherical body dropping onto a water surface is measured using the method which has been proposed by us. In the method, a cube corner prism is embedded in a metal spherical body. The optical center of the cube corner prism coincides with The center of gravity of the spherical body . The motion of the spherical body is measured in the optical interferometer. The velocity of the spherical body can be calculated from the Doppler frequency measured in the interferometer. The acceleration, displacement, and inertial force of the spherical body can be calculated from the velocity of the spherical body. The dropping distance of the spherical body is variable. In this experiment, the distance is set to approximately 60 mm, 150 mm, and 190 mm, so that the difference of impact force caused by the difference of initial velocity is evaluated in detail.

Highlights

Water impact, water entry, or slamming is a complex nonlinear phenomenon, which is especially important in the fields of naval architecture, ocean engineering, aerospace engineering, and fluid engineering
We have previously developed a method for precise mechanical measurement known as the Levitation Mass Method (LMM)
In the LMM, a mass levitated by an aerostatic linear bearing is used, and the laser Doppler interferometer is used for measuring the velocity

Summary

Introduction

Water entry, or slamming is a complex nonlinear phenomenon, which is especially important in the fields of naval architecture, ocean engineering, aerospace engineering, and fluid engineering. It has been difficult to measure the mechanical quantities precisely, such as the impact force acting upon the object from the water surface. We have previously developed a method for precise mechanical measurement known as the Levitation Mass Method (LMM). In the LMM, a mass levitated by an aerostatic linear bearing is used, and the laser Doppler interferometer is used for measuring the velocity. A method to measure the impact force of a spherical body dropping onto the water surface has been proposed by modifying the LMM(12). A cube corner prism is inserted in the stainless spherical body and the inertial force of the spherical body is measured using the laser Doppler interferometer. The acceleration, displacement, and inertial force of the spherical body are measured precisely in the study. The dropping distance of the spherical body is changed, so that the velocity of water entry of the spherical body is changed, and the phenomenon of the collision between the spherical body and water surface is evaluated in detail

Experiment

Results

Conclusions