"An adverse pressure gradient strongly favors transition to turbulent ﬂow. In contrast, strong favorable pressure gradients (where p decreases in the downstream direction) tend to preserve initially laminar ﬂow." "High values of M∞ and low values of Re tend to encourage laminar ﬂow" Looking at those two statements from the "fundamentals of aerodynamics", I think the fluid velocity alone does not determine whether the fluid will be laminar or turbulent.(high V gives high mach number but also high Reynolds number). Can someone explain why/how the mach number comes into play? I would also like to know why an adverse pressure gradient favors transition to turbulent flow. Thank you!