Aeronautics

Computational Study of a Small Ducted Propeller

Image from simulaton of Titlduct vehicle blade tip
Video showing a slice through the computational mesh of the six-passenger Tiltduct concept vehicle, colored by vorticity magnitude. As the blades advance through the slice, the tip vortex can be seen being created by the blades and then moving down as the next blade advances. Watching the mesh itself demonstrates how the use of OVERFLOW’s adaption allows for the mesh to dynamically change along with the movement of the blades. Timothy Sandstrom, James Jensen, NASA/Ames

As part of the Revolutionary Vertical Lift Technology (RVLT) project to help develop the next generation of vertical lift vehicles, ranging from air taxis to large cargo transports, researchers from NASA’s Ames Research Center are using agency supercomputers to simulate the physics around a ducted propeller design. The Tiltduct—a six-passenger prototype being developed under the RVLT project—uses six ducted propellers that can tilt 90 degrees to allow for vertical and forward flight. The Ames Computational Aerosciences team simulated a single propeller of the Tiltduct design, with the goal to better understand what methods and grid resolutions are required for computational analysis to be an accurate and cost-effective tool for agency engineers. This ducted propeller is ideal to achieve that goal, since experimental data from a wind tunnel test performed at NASA’s Glenn Research Center was available and used to assess the accuracy of the computational simulation results. The results of the single ducted propeller simulations and lessons learned will then be used to establish the best methods for future simulations of a full vehicle where multiple ducted propellers are present.

Quick Facts

Accurately capturing the physics involved in this problem required running large simulations for long periods of time. Each case was using a few hundred CPUs and required a week of wall-clock time to run, which is something that is only made possible through the use of NASA’s supercomputers.

James Jensen,
NASA Ames Research Center
  • The project involved running time-accurate simulations of a rotating propeller using NASA’s OVERFLOW computational fluid dynamics code, while studying a variety of simulation parameters, including refinement of the computational mesh and selection of different numerical schemes to optimize and improve simulation accuracy.
  • Over the course of the study, the team found that using the automated mesh adaption tool in OVERFLOW led to much more accurate predictions of the physics around a ducted propeller without much penalty to the amount of computational resources needed to run a case.
  • The results and best practices developed over the duration of this Tiltduct study will used by groups across NASA for future analysis of vehicle concepts that utilize ducted propellers.
  • On average, each simulation from this case required the use of about 300 CPUs run for over a full week on the systems at the NASA Advanced Supercomputing facility at Ames.

Researchers

  • James Jensen, NASA Ames Research Center
  • William Chan, NASA Ames Research Center

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