In engineering situations, elevations are generally small compared to the size of the Earth, and the time scales of fluid flow are small enough to consider the equation of state as adiabatic. In this case, the above equation for an ideal gas becomes: v 2 2 + g z + ( γ γ γ γ − − 1 ) p ρ ρ = constant (along a streamline) where, in addition to the terms listed above: