Woodruff School of Mechanical Engineering
Flight Dynamics of Explosively Driven Fragments
Dr. Peter Yeh
Sandia National Laboratories
Friday, October 20, 2017 at 12:00:00 PM
MRDC Building, Room 3403
Upon explosive detonation, fragments of all shapes and sizes are launched outward at very high speeds, typically in the supersonic range. Depending on its shape and initial conditions, a single fragment can travel great distances in an uncontrolled flight as well as turn and tumble. Understanding and characterizing the full six-degree-of-freedom (6DOF) dynamics, trajectory, and possible tumbling modes of even a single fragment remains challenging for both computational modelling and experiments. Current estimations of fragment trajectories usually employ a single drag coefficient to characterize the air resistance, but this cannot capture the rotation and tumbling of an uncontrolled fragment with high aspect ratio. This talk presents an overview of our current research progress in both simulation and experimental efforts to understand the dynamics of fragment flight. Using a combination of a compressible flow solver and rigid body dynamics integrator, a novel fragment trajectory simulation methodology using existing SNL tools is developed, and the physics of a representative fragment in flight is examined using these tools. Fragments are found to have mostly chaotic flight trajectories as expected, but exhibit some order as fragments tend to settle on rotation and precession about one of two stable inertial axes. Furthermore, a series of ballistics experiments were conducted to image a projectile in supersonic uncontrolled flight and measure their 6DOF trajectories as validation data for our simulations. Preliminary comparisons between experimental and simulation data support the validity of our simulation methodology as external flow structures over a fragment exhibit excellent agreement.
Peter Yeh is a staff scientist in the Computational Shock Physics department at Sandia National Laboratories. He received his PhD in Mechanical Engineering from Georgia Tech in 2016 with a focus in fluid mechanics studying the performance of flexible flapping plate propulsors. His current research interests at Sandia include computational mechanics, computer vision, and data science techniques for technology development in national security applications.
Refreshments will be served.