Thanks Burke, I think this will solve my problem. However I am trying to implement it this way but I am never able to get the actual value of the variable.
I am passing a random number (as string) to the flow and the rest I am doing as the post suggest "testFlow" + #randNumber. This seems to take effect as I see testFlow for execution runs but the randNumber that I input does not show up. The execution runs have the name 'testFlow + #randNumber'. I tried the same with #__randNumber, but no effect. Any idea what I might be missing here?