Fraser Subsonic Diffuser. Skin Friction Coefficients. x (m) cf () 1 11 0.1168 0.00349 0.1582 0.00344 0.2106 0.00286 0.2365 0.00219 0.3000 0.00146 0.3813 0.00085 0.4384 0.00061 0.4684 0.00056 0.5227 0.00034 0.5776 0.00027 0.6421 0.00018