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Impact physics of solid shapes impinging on solids and liquids and aerodynamic behavior of airfoils in high-speed flow
Dissertation   Open access

Impact physics of solid shapes impinging on solids and liquids and aerodynamic behavior of airfoils in high-speed flow

Hussein A. Bassindowa
Doctor of Philosophy (Ph.D.), Drexel University
Jun 2026
DOI:
https://doi.org/10.17918/00011508
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Abstract

This research explores the realm of studying impact physics through the tool of numerical simulation using computer software. The purpose is to be able to propose, analyze, and infer viable solutions for complex problems without the time, space, and budget constraints associated with field experiments. The main problems explored in this paper deal with solid-solid and solid liquid impact. Solid-Solid and Solid-Liquid impact is an area of physics that covers several topics important to industrial safety, transportation, non-destructive tests, and military tech to name a few. This work presents an overview of several topics related to impact physics which are solid-solid ricochet, solid-liquid ricochet, and the Split Hopkinson Pressure Bar (known as the Kolsky bar) as well as aerodynamic behavior of an airfoil under high-speed airflow. The topic of a ricochet off a solid surface shows a projectile launched at a plate at different speeds (250 to 1500 m/s) at different angles (between 25° and 60°) for an aluminum and titanium alloys (used interchangeably), the ricochet behavior is observed to further explore a mathematical model proposed by one of contributors of this work. Ricochet off a liquid surface is explored by studying the ricochet of a spherical object made of different materials (steel, duralumin, and titanium alloy) off an air-water interface at different angles (between 2° and 11.5°) and at different Froude numbers (between 100 and 90000) to determine a mathematical expression of the critical incidence angle as a function of the Froude number and the material of the projectile. The flow and heat transfer characteristics of high-speed air over an airfoil initially at temperatures of 200 K and 300 K, respectively, are investigated. Two types of airfoil are considered, the NACA0012 and the symmetrical double wedge airfoil. The free-stream air flow velocity is set at subsonic and supersonic (Mach=0.8 and 1.5, respectively). The LSTC propriety transient solver LS-DYNA is used to generate different resulting shock wave formation using the CESE (conservation-element solution-element) method. Finally, the use of the Kolsky bar (also known as the Split-Hopkinson pressure bar. SHPB), is probably one of the most common way of, experimentally, finding material properties at high strain rates, including the widely used strain versus stress curve. The standard Kolsky (compression) setup includes 3 bars: the striker, the incident bar, and the transmission bar. The development of a dynamic LS-DYNA model to characterize a standard Kolsky bar is reported first. Followed by a three-point Kolsky bar method that is suitable for measuring the flexural strength of ceramics in a high-rate three-point bending configuration. The three-bar arrangement used in this case - one incident bar and two transmission bars - to provide measurements of force and displacement at each loading point. Small diameter bars are used to improve the force measurement made by the incident bar which in many cases would be inaccurate. The developed model is formulated to predict the desired incident pulse, based on the conditions of the available experiments and the desire for a prescribed strain-rate as found in the three-point Kolsky bar.

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