Jan
21

Mechanical Engineering Dissertation Defense

01:50 PM - 03:00 PM
Online & Home
Contact:
Michael Hargather

Kyle Winter, a Ph.D. candidate in Mechanical Engineering will be defending his dissertation titled "Irregular reflections of unsteady shock waves".  The event will be held via Zoom: 

Zoom Url: https://zoom.us/j/92908687098
Zoom Meeting ID: 929 0868 7098

Abstract:

The majority of prior research in the field of shock wave reflections has focused on pseudo-steady reflections which are fundamentally different from the most common case of explosively-driven unsteady shock waves. The present work combines prior reflection theory with new models, methodologies, and scaling to better predict and understand unsteady shock wave reflections. Analytical models developed here allow the prediction of shock wave reflection type, overpressure and impulse, for explosively-driven shock waves for any charge size, height of burst, or distance from the charge.
Experiments were performed using gram-scale charges of PETN and kilogram-scale charges of PBXN-110 to generate data for comparison to the models. The experiments used refractive imaging to visualize the shock wave propagation and reflection. Using the shock Mach number determined from the imaging systems and the height of burst, the type of shock reflection was predicted and shown to agree with the measurements. Using the Mach number and height of burst the overpressure of the shock wave reflection was estimated through the analytical models and shown to agree with the experimental results.
A methodology for calculating reflected pulse duration was proposed and shown to match the experimental data better than previous models. The pressure decay process was predicted using this new methodology and the Friedlander decay coefficient evolution with distance was explored. The decay coefficient was found to vary for non-reflected and reflected shock waves and to vary with explosive. By comparing the decay coefficient between the charges, a scaling approach that uses the heat of reaction for scaling the coefficient was proposed to account for differences between explosive.