How to find the reflections of the pressure wave in pipe lines
 

Hi I am simulating the pressure waves (pressure transients or pressure surge or water hammer) in pipe lines. Question is, how to find the reflection of the pressure wave when it is hitting at sudden contraction at particular section along the length of the pipe.
If the pipe diameter is uniform, then the reflection will be at boundaries but if the there is any sudden contraction in the pipe line , there will be reflections at these locations, how to find them?

I am really need of this, if some one give any reference papers or any code or any book , it will be really help to me,


Thank you