Subashni Ravichandran
Forum Moderator

Hello M Rizuwan

First as I mentioned, Fluid Solid simulation (FSI) is currently not possible in Discovery.

You will need to make a split in the tank geometry to represent the height of the Fluid and manually apply pressure (as shown in the example) on the surfaces that are in contact with fluid. 

See image below.

Although, as changing the thickness will interfere with the contacts and also the Split created to represent the Fluid level, currently, you will need to update these for each case manually.