Kinetic time-step limiter
Adding the kinetic time-step limiter to resolve the problem when particles that receive high velocity kicks from kinetic feedback free-stream through their neighbours due to their large (initial) time-steps.
The current implementation of this time-step limiter has been tested with a single isolated (E=1e51
erg) supernova that releases all its energy in kinetic form. Without the limiter, the gas particles that receive the highest kicks traverse unrealistically large distances before they begin interacting with their neighbours. If this happens, a realistic blast-wave does not form. This effect is mitigated if the initial (prior to feedback) signal velocity v_sig
is increased. When the time-step limiter is switched on, the blast-wave always has the correct momentum, shape, density and other physical properties, all of which are independent of v_sig