Question 4 (a) State the conditions under which the Blasius solution is valid for a laminar boundary layer (b) Air at a temperature of 60C is flowing at 0.4 m/s across a flat plate. At a point 20 cm downstream of the leading edge of the plate, calculate (i) the velocity at a distance distance 6mm from the plate. (ii) the boundary layer thickness 899 at this point. (c) An alternative analysis of the laminar boundary layer is to use an approximate solution for the velocity profile in the layer. The profile Ux 3 1 Y where = U 2 899 is commonly used for this. (i) Explain why this profile would be a good Anzatz solution for this case. (ii) Derive an expression for the displacement thickness &* using this expression (iii) What is the value of 8* at the point 20 cm downstream of the leading edge of the plate? (iv) Derive a similar expression for 8* for the Blasius solution. How do the expressions compare?