The freestream is the air far upstream of an aerodynamic body, that is, before the body has a chance to deflect, slow down or compress the air. Freestream conditions are usually denoted with a ${\displaystyle \infty }$ symbol, e.g. ${\displaystyle V_{\infty }}$, meaning the freestream velocity.

References

• Anderson, John D., 1989. Introduction to Flight, 3rd Ed. McGraw-Hill