Parametric Study for Directional Stability of Tumbling Plates by Wind Tunnel Testing

Mitsuo Ishiguro,Yoshiaki Miyake

doi:10.12792/jiiae.10.1

Abstract

The tumbling phenomenon is considered to be an important phenomenon for aircraft flight safety because of the possibility of falling objects from the aircraft reaching far away or for knowing the behavior of falling roof tiles blown off by strong winds. Therefore, many tests to measure the force act on the tumbling plate in wind tunnel have been conducted. The authors have been studying the directional stability of the tumbling plate [9], which has a great effect on the reach of falling objects, and have proposed a non-contact measurement method wind tunnel test method from the viewpoint of dynamic balance which can acquire the force without force sensors [12] Here, we call “towing wind tunnel test method”. In this paper, for the evaluation of the directional stability of the tumbling plate, we parametrically changed the planar configuration of the tumbling flat plate and measured the acting force in wind tunnel using this towing wind tunnel test method. As a result, the relationship between the shape of the tumbling plate and the conditions for directional instability was clarified.

Highlights

When an object falls in a fluid, continuous rotation by the action of fluid force is called autorotation
The L/D obtained by wind tunnel test are almost included in error bar of L/D obtained in the preliminary free fall test and can be said to show a good agreement
In order to investigate the directional stability of the basic configuration, the force was measured in a wind tunnel test using the towing wind tunnel test method

Summary

Introduction

When an object falls in a fluid, continuous rotation by the action of fluid force is called autorotation. As motion modes, tumbling, flat spin, corning, etc., are known. The drop direction and the rotation axis are vertical is called tumbling. Tumbling is known as natural phenomena such as leaves of trees and roof tiles blown away by typhoons, and important phenomenon in aerospace engineering and meteorology as well as scattering region estimation of satellite/rocket fragments damaged during atmospheric reentry and objects dropped from aircraft at random. Many studies have been conducted due to clarify the tumbling phenomenon and how the speed and glide ratio of the falling object change depending on conditions such as Reynolds number and aspect ratio [6] [7], and some empirical equations have been proposed [8]

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Conclusion