What is the Reynolds number outside boundary layer region for flow over flat plate?

When a fluid flows over a horizontal flat plate, we know that a boundary layer is formed. The flow in this boundary layer starts out laminar and then can become turbulent. What is the flow regime outside the boundary layer? Intuitively I feel it's laminar because all the fluid particles are moving with same velocity in the same direction, it's a highly ordered flow. However, if we look from the perspective of Re, the inertia forces and viscous forces are both zero which suggests that Re = 0/0.

Reynolds no. for laminar flows is low, and if the flow outside the boundary layer is laminar then it should be small (maybe approaching zero), but 0/0? I'm not able to comprehend that.

• Why are you saying that the inertia forces are zero in the outer flow? Commented Aug 1, 2021 at 22:11
• Because there are no velocity gradients in the outer flow. The particles are not accelerating. Commented Aug 2, 2021 at 11:25