Clearing results of a simulation deletes all results related to this simulation and cannot be undone. To clear results of a simulation, choose in the Configuration group on the Simulation ribbon. This button is only enabled if no jobs for the simulation are currently running.
You can also delete all results but the initial mesh from a simulation. A subsequent Simulate action will then start the AMR (adaptive mesh refinement) from that initial mesh, eliminating the time associated with recreating the intial mesh.