International Journal of Advanced and Applied Sciences
Int. j. adv. appl. sci.
EISSN: 2313-3724
Print ISSN: 2313-626X
Volume 4, Issue 9 (September 2017), Pages: 70-79
Title: Instability estimation of irregularly shaped bodies moving through a resistive medium with high velocity
Author(s): Elvedin Kljuno *, Alan Catovic
Affiliation(s):
Mechanical Engineering Faculty, University of Sarajevo, Sarajevo, Bosnia and Herzegovina
https://doi.org/10.21833/ijaas.2017.09.009
Abstract:
The purpose of the paper was to show an idea how numerical simulations of flow around a stationary irregularly shaped body can be used to estimate instability of the body during a real-world motion of such a body (e.g. a metal fragment). To the best of our knowledge, there is no evidence that such an analysis is available in literature for irregularly shaped bodies. The novelty is in the introduced method for the stability analysis and the fact that a real-world fragment shape was digitized and used for the analysis. However, the disadvantage is in necessity that real fragments need to be scanned and digitized for the analysis, but the future work should give improvements in this direction. The focus was on the rotational part of the motion, particularly on obtaining the period of the motion when the body rotates, but the solving for angles of rotation was not the objective. We showed an idea on how to estimate the period of instability when continuous rotation occurs after the initial projection of the fragment. We assumed that relatively high angular velocity occurs at the initial condition (initial projection of the fragment), which provided an opportunity to assume further that the axis of rotation remains unchanged during the motion. By analyzing the kinetic energy of rotation, we estimated the period of body rotation until it reached a stable orientation during the high velocity motion. To employ this approach that uses the mechanical energy, it was necessary to obtain the work done by the (aerodynamic) moments of resistance forces about the center of mass. These resistance (aerodynamic) moments were obtained for various orientations of the body using simulations of fluid flow around the real geometry of the body, which was obtained by scanning a real-world fragment, digitizing it, and importing it in a CAD software, which provided the inertial properties through moments of inertia. At each rotation, the kinetic energy of rotation is dissipated through work of the aerodynamic moment which was the basis for calculation when the body takes a steady orientation for the rest of the motion.
© 2017 The Authors. Published by IASE.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Keywords: Fragment, Aerodynamic force, Orientation instability
Article History: Received 8 June 2017, Received in revised form 27 July 2017, Accepted 29 July 2017
Digital Object Identifier:
https://doi.org/10.21833/ijaas.2017.09.009
Citation:
Kljuno E and Catovic A (2017). Instability estimation of irregularly shaped bodies moving through a resistive medium with high velocity. International Journal of Advanced and Applied Sciences, 4(9): 70-79
http://www.science-gate.com/IJAAS/V4I9/Kljuno.html
References: