hi rwoolhou,

1. As written in UDF,  as far as my understanding solver uses value in between the timestamp as mention. E.g : After 1000s and till 1100, v=1.5m/s and if >900 and less than 1000,v=1.35.

Please correct me if i am wrong.

2. I get some negative Delta p values,as velocity step increases. Any suggestions??

Velocity is lower at P1 and higher at P2 as expected but Pressure is not stable.