Cockrell and Markland have found that the static-pressure recovery coefficient of a conical diffuser, which is well known to decrease as the (turbulent) boundary layer thickness at entry increases, actually rises again when the inlet boundary layer is so thick as to approximate to fully-developed pipe flow. It may be noted that this is not a consequence of the definition of the pressure coefficient because, for typical pipe flow velocity profiles, the pressure coefficient based on mean velocity, , is very nearly the same as that based on momentum flux .