Dear Onur,

Please find the attached article. These articles may help you.

First of all you need to study the types of shock absorbers. There can be many methods to absorb the shock with or without the use of a fluid. In your case, probably, you are referring to telescopic shock absorbers using hydraulic fluid passing through a restricted orifice for the purpose of absorbing the shock. In this case, the physical design process is very similar to any other hydraulic cylinder. These hydraulic cylinders are used in abundance in heavy machinery, construction machinery etc. As far as I know, it is one of the most commonly used method to absorb shock in most of the vehicles. For CFD analysis, it is better to select something which is not very well understood by conventional tools while in case of shock absorbers or hydraulic cylinders, these are very well established and time tested items with hydraulic oils. However, if you want to work on optimizing the oil properties through modern additives, it can be a worthwhile task. An example of an analysis on visco-elastic effects in engine oil can be seen in the link below:

Conference Paper Modeling Low-Viscosity 1st Compression Ring EHL at Large Rad...

For meshing, you can always open the cylinder wall and consider it a rectangular piece.

Try moving mesh. Its not hard