fan speeds the pressure was measured just upstream of the nozzle using a shortridge instruments model adm 860 electronic micromanometer in all cases 12 separate readings were averaged at each fan speed as shown and unexpectedly the pressure drops in this embodiment of the improved nozzle were effectively equal to the pressure drop in the conventional design this was a surprising result in that the superior flow uniformity achieved from the addition of directional 15 did not come at the cost of imposing a higher pressure drop fig9 shows the variation in the velocity uniformity parameter as a function of the number and therefore overall thickness of the honeycomb material inserted between the perforated plates of this embodiment where there were multiple pieces of honeycomb material they were arranged so that the adjacent faces were essentially touching with no gaps the flow uniformity improves as the number of pieces or layers of 12 7 mm thick honeycomb material increases after 6 pieces or 76 mm total depth the uniformity parameter was judged to be approaching the limit of resolution of the measurement system fig1 shows the variation of the velocity uniformity parameter as a function of the number of honeycombs at a fixed overall honeycomb depth or thickness of 76 mm in this case various different thickness pieces of honeycomb were used to achieve a constant total thickness so that the variation between the trials was that there were a different number.