How can I get a simulation software for a mechanical machine design?
Lot of design / CAD software is available in the free domain -
2. Fusion 360
7. 3D Slask
I think this should be a good starting point.
I would add this to the excellent list given by @ Kaustubh:
ANSYS is a world leader in engineering simulation for both steady and transient state of fluids. Not only that, it has a wide range of add-ins for static and dynamic structural simulation and thermal simulation as well. ANSYS is providing one-year free license that you can get from here:
Also, you can get 3-year free license of Autodesk Fusion 360 here which also provides a vast variety of simulation products: