The Delete Mesh command is located in the context menu that appears when you right-click the Mesh Model heading in the browser (model tree). It deletes the mesh on all the parts for the current analysis.
The program prompts you to verify that you want to delete the mesh. Additionally, if the analysis has already been run (and results exist), you will see a warning prompt.
The current results are dependent on the mesh. Deleting this mesh will also delete the results.
This warning gives you a second chance to cancel the deletion request.