Geometry of centrifugal pump
 

Hello everyone
I am working on centrifugal pump simulation case, i have just reviewed some previous published simulations of the same case, in some cases i found the inlet pipe extended to the impeller inlet and sometimes i found it extended to the casing body only
What are the factors determine the end of the extension of the inlet pipe?
https://prnt.sc/d_06qDcoQgLm
That is the pump i am trying to simulate, if someone can recommend the shape of geometry of inlet ot will be a great help for me