Mat-1.3656 Seminar on
numerical analysis and computational science
Monday, May 12, 2014, room M233 at 14.15, Eirola & Stenberg
Heikki Kahila, Aalto!
Engine exhaust plume interactions with a planetary surface
When a planetary lander descends, the rocket engine exhaust plume impinges
on the planetary surface and entrains solid soil particles into a ow. These
eroded particles accelerate to high velocities and form dangerously energetic dust
sprays. The dust sprays decrease visibility and jeopardize the landing vehicle and
hardware nearby. The understanding of the risks is important to improve the
safety of the future planetary missions.
This Master's Thesis contributes to this objective by introducing a three-stage
simulation framework. In space the exhaust plume expands into a vacuum
and becomes a rareed uid. A continuum hypothesis of the Computational
Fluid Dynamics (CFD) breaks down and therefore a molecular level simulation
method, The Direct Simulation Monte Carlo (DSMC), should be applied. The
plume impingement in a lunar environment was modelled by a one-way coupled
CFD-DSMC simulation framework. The lunar surface erosion was modelled as
a stochastic process and the soil particle trajectories were computed from the
interactions between the particles and the ow eld. The ow eld was obtained
as an output data from the DSMC simulation.
The simulation framework was successful and provided qualitatively comparable
results for the plume ow eld and the impingement phenomena with respect
to the results in the literature. The resulting soil particle trajectories indicate
a dependence on the initial conditions. The range of the soil particle trajectory
is suggested to correlate with the initial vertical velocity. The slope of the trajectory
was proportional to the particle diameter. The applied formulations for
aerodynamic forces in a rareed ow were found cumbersome and constrained. In
addition several minor remarks have been discussed.