Thanks Navendu and ray for the prompt reply. But Ray,I think, my question is little bit misinterpreted. In clear words, I wanted to know whether whatever navendu is saying, is correct or not. That is can we feed two impulse in the DLF generator to take care of periodic nature of slug ?.

In TIME HISTORY analysis also, as told by you, load will be applied for the time specified in history with load. For the rest of the duration , it will be zero. Now
can we give the two impulse to take care of periodic force due to slug. Giving an example, if slug is hitting elbow after every 1000ms and stay with it for 100 ms. can we feed time history as follow
0 F
100 F
101 0
1000 0
1001 F
1101 F
and continuing in this manner uptill say 20 cycles to take care of periodic nature. (Offcourse, load duration in control parameter should be greater than time for 20 cycles.