Piping Discharge Submerged in Fluid

[smo12345]

I'm modeling piping that discharges into an open basin. Let say the pipe is running 10' in the vertical direction. The pipe is submerged under the top of the fluid 3'. I'm wondering how to model the resistance of a fluid so that I can get proper displacements under a seismic event. I have a uniform seismic load. What I have done is break the section of pipe that is submerged into 1 foot segments and used a flexible guides at each 1' segment. I assigned a resistance of 5 lb/in, 10 lb/in and 15 lb/in respectively. However, I have done no calculations to come to these numbers. Just my assumptions.

Does anyone have any suggestions regarding my modeling technique or an alternative modeling method? I need to include the resistance of the fluid during the uniform load. Without it my displacement results are not reasonable.

Thanks in advance.