(2− *K*) / (2 + *k*)

This expression implies that if *k*=2, the non-uniformities are completely removed. The analysis by Batchelor [53] indicates that the reduction factor can be more accurately expressed as:

$$(1 - \alpha + \alpha \ K) \ / \ (1 + \alpha + K)$$

where *α* is the screen deflection coefficient defined as the ratio of (air exit angle)/(air entry angle)

Taking the approximate value of α [56], the reduction factor for k=2 and α =0.64 is seen to be 0.1. Batchelor gives the theoretical reduction for V or transverse velocity non-uniformity component as α or 0.64 for a screen of resistance coefficient 2.0.
