An investigation has been conducted to determine the effect of both six— and eight-blade dual—rotation propellers on the internal—flow characteristics of an NACA 1—series D-type cowl, and the effect of the cowl on the characteristics of the propellers. The pressure recoveries at the cowl inlet and the characteristics of the propellers were measured at Mach numbers from 0.13 to 0.84, inlet velocity ratios from 0.27 to 1.08, advance ratios from 0.80 to 7.29.> and propeller blade angles from 40° to 70°. Included are results of surveys, with the propellers removed, of the local velocity distributions ahead of the cowl, measured in the planes of both the front and rear components of the dual—rotation propeller, for an NACA 1—46-5—085 spinner, and in the plane of a singlerotation propeller, for the shorter NACA 1—46.5—O47 spinner. All tests of the dual—rotation propeller—spinner—cowling combination were conducted with the model at an angle of attack of 0° and at a Reynolds number of 1.0 million per foot (1-3 million based on the maximum cowl diameter).
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