Simulation speed

If I run multiple simulations (from different tabs of Linux terminal), then is it going to slow down each simulation?

I meant, if run multiple simulations at a time from different tabs of linux terminal, then will it slow down each simulation?

It will if you exceed your systems resources. If you have 10 cores and run 4 serial simulations, then it will not. But if you have 10 cores and try to run 4 parallel simulations (4 processes per run), then it will because you will be running 16 (4x4) processes on 10 cores.