Particle Adhesion
  • particular area of interest for moonlet stability, varying the particle adhesion force will allow us to approximate forces of friction acting between the ring particles in a patch, and adhesion force has now become an additional variable changed via command line (AdhesionSim is the makefile)
  • Additionally, this experiment explores more the conditions necessary for propeller formation, and specifically constraints on the propeller-forming moonlets.
  • The background simulations from the moonlet stability experiment are still useful, mainly as an environment to place and test for collision stability the naturally-formed moonlets from last semester.

Thus far the adhesion force does not seem to affect the rate of accretion for ring particles, even when greatly exaggerated. Our solution has been to use a square accretion forcing model instead of a smooth one so that the force acts strongly when the particles are a certain range of distances away and then disappears completely. This had caused a marked increase in clumping of the ring material, but we are still struggling to form moonlets at 130000 km with this force. The clumps are not localized enough and their spread geometry causes shearing to occur and continually break up the largest clumps in these simulations. A big problem is computational power, since the background simulations require a great number of particles in the background in order to be accurate, and the moonlet accretion simulations have to keep track of many particle collisions. Both of these simulations are slow-going and great care must be taken when setting them up so that they will not have to be cancelled and restarted later.

We have now restarted the moonlet accretion simulations with new boundary conditions that are more agreeable for moonlet formation due to the lack of y axis overlap (causes excess shearing forces acting on the ring particles, much more difficult for moonlets to form).