# Boundary Layer displacement thickness

## Main Question or Discussion Point

Hey guys,

The streamlines just outside a boundary layer are pushed away from the wall by the displacement thickness $$\delta$$* and I understand that;

$$\delta$$*=$$\int^{\infty}_{0}$$(1-$$\frac{u}{U}$$)dy

Now this is for flow over a plate with length x=4m. At x=0 is the leading edge and at x=4 $$\delta$$ = $$\delta^{b}$$

Now been told to find the equation of the streamline i.e. y=y(x) that touches the boundary layer at x=4 (and y = $$\delta^{b}$$ I guess).

I know I have to calculate the boundary layer displacement thickness...but I am unsure of how to do that and what I should do after that.