Advice on modeling (piston - air - floating piston - air - wall)
 

This is my first post on this forum. I have not found any thread that helps me solve this problem specifically.

I am attempting to model the system shown in the image "Case Setup" using Ansys Fluent. This system is part of a hammer drill. In a nutshell, the main purpose of this is to have the striker hit the anvil and transmit energy through the anvil to a chisel without touching this piston. The right control volume is well vented, and the left volume has one small vent.

It is also good to know that I am very new to Ansys, as this is my first time using it (after doing some tutorials). Nonetheless here are my questions/concerns:

(1) Is it possible to only use a 2D domain to include modeling the six larger vents by using some sort of scaling factor? If not, could I model a similar setup using only two vents (one on each side) on the cylinder walls?

(2) I have been working in parts, and on one case setup I only modeled the volume V2 assuming I knew the motion of the striker (which I don't). I essentially wanted to learn how to set the dynamic mesh such that it can simulate contact between the striker face and the anvil. I get negative volume results just before the walls touch.

I am not sure if I have to use topology to map the two edges together and/or utilize 3D mesh for this. See "Negative Volume" image to see what the mesh looks like once the error shows.

However, I also would like the striker face to rebound off the wall. If the contact is not possible in 2D, can I setup a code to force the striker to have a negative velocity (rebound) once it gets very close (as shown in the attached image)?

(3) Do you believe I have to use a coupled analysis for this? I think I have to but was also thinking that if I can use a 2D mesh, could I also just make one mesh with very thin regions around the striker walls between the cylinder and striker and try to use the gap model to assume zero flow between the surfaces.

(4) Generally, not specific to this case. Am I able to assign a mass to an enclosed volume in a 2D domain such as mass per unit depth and also apply Newton's Second Law to this 2D mass? If so, is there an option in Ansys to easily set this up, or is this something I would have to apply programmatically using a udf file

(5) Any additional advice, strategies, methods, examples, etc. would be very appreciated. Also, please let me know if you need more clarity.

I really appreciate everyone’s time and consideration reading this post. It means a lot to me.