Hello Folks, I was wondering if anyone could tell me what is meant by "shock excursion"? I'm quite new to unsteady transonic aerodynamics and have seen this term in a few papers but haven't understood what is meant.

Cheers F

In unsteady transonic aerodynamics, a shock can move relative to the reference frame (unlike the steady case). The term "shock excursion" should refer to either (a) the fact that a shock moves (outward, generally) instead of remaining in place, or (b) the distance covered in such motion. For example, the so-called "unstart" of a supersonic inlet involves excursion of the shock upstream and subsequent spillage of the shock out of the inlet into the supersonic flow upstream of the inlet to form a bow shock. I am unaware of any specialized meaning for "shock excursion" in transonic aerodynamics. The term "excursion", as applied to objects, retains its ordinary English meaning. For example, one speaks of the excursion of a drill bit in a drill. Perhaps, though, you are already aware of this usage.

Thanks Ananda that's a big help.

This is the definition I had assumed but I thought I had best check to make sure I didn't look silly in front of my boss )

Cheers Frank