Wind tunnel performance comparative test results of a circular cylinder and 50% ellipse tailboom for circulation control antitorque applications
Fisher, David T.
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A low speed wind tunnel study to quantitatively evaluate the performance (lift and drag) of a circular cylinder and comparable 50% ellipse was conducted. Circular cylinder performance was evaluated at slot positions of 80 deg to 135 deg, measured relative to freestream; 50% ellipse performance was measured for angles of attack between -5 deg and 30 deg. Tests were conducted at three blowing coefficients, 0.3, 0.4 (optimal historically) and 0.5, to evaluate tailboom performance sensitivity. Circulation control test results revealed optimal c1 values at an approximate 116 deg slot position, corresponding to cd values no greater than that of a smooth cylinder. The 50% ellipse results revealed optimal c1 values at approximately 18 deg AOA, though associated with considerable drag. For all three blowing coefficients, the circular cylinder L/D values were consistently three to four times greater than their 50% ellipse counterparts. Recommendations for future NOTAR(TM) tailboom design modifications and later research are made.
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