NFA Simulation of a Planing Boat in Waves

The video shows a high-speed planing boat accelerating from rest to a constant forward speed in head seas. The boat is permitted to have four degrees of freedom, including sway, heave, roll, and pitch. The non-dimensional pressure acting on the bottom of the boat is shown in the lower right-hand corner. The bottom plane shows the caustics that are formed as light is refracted by the ocean surface. A view looking at the bow of the boat is also inset into the video in the lower left-hand corner.

The Numerical Flow Analysis (NFA) code has been used to perform the simulation on the Cray XE6 at the Air Force Research Laboratory (AFRL) supercomputing center. NFA uses a Cartesian-grid formulation to solve the Navier-Stokes equations with a volume-of-fluid method to track the free-surface interface. An implicit sub-grid-scale turbulence model is used to model turbulence. The simulation uses 805 million grid cells and is run using 3,072 processors for 70,000 time steps. The simulation uses 190 wall-clock hours.

The video shows a side view of the boat. The bottom plane beneath the boat shows the caustics that form as light is refracted by the ocean surface. A view looking up at the bow is inset in the lower left-hand corner. The non-dimensional pressure is also shown in the video in the lower right-hand corner. Note that the pressure is normalized by rho U^2, where rho is the density of water. The highest pressures occur along the spray root when the boat slams into the waves. Spray is shed along the sides of the boat. The water separates cleanly from the boat's transom, which is dry as a result. Waves break at the rooster tail behind the boat and along the edges of the Kelvin wake. The ambient waves form spilling breakers toward the back of the computational domain. The greatest amount of wave breaking and spray generation occurs when the boat slams into the waves. During slamming events, the personnel on high-speed planing boats are subjected to very high accelerations that can lead to debilitating injuries.

We are very grateful to Dr. Michael Stephens, Chris Lewis, Richard Walters, Miguel Valenciano, and Michael Wissmann from the Data Analysis Assessment Center (DAAC) at the DoD High Performance Computing Modernization Program for making the animations. Check them out. The Office of Naval Research funds our research. Our program sponsors are Dr. Steven Russell, Dr. Thomas Fu, Dr. Patrick Purtell, Dr. Paul Hess, Dr. Robert Brizzolara, Dr. Ronald Joslin, and Dr. Thomas Drake. Dr. Douglas Dommermuth, Thomas O'Shea, Dr. Kyle Brucker, Lucas Rhymes, and Donald Wyatt from Science Applications International Corporation develop NFA. We are grateful to Dr. John Levesque at the Cray Supercomputing Center of Excellence who improved the MPI communication.