@Rob, I even tried using just the fluent alone and check if changing the input parameter cause any changes in the output parameter. I tried the same step without fsi creating model> assiging the fluid to cell> providing inlet P condition with the input parameter> intiailzie the solution > run > results> surface avg outlet vel> save outlet param> save the fluent setup by using the change for current and future calculation > close fluent clicked on the parameter and started input different design points and still same answer ...this making bit frustrated rare occasion it runs and other time just give me the same value. 

any suggestion