Use of the Coanda effect for obtaining jet deflection and lift with a single flat-plate deflection surface

Author / Creator

Von Glahn, U., author

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Online

Summary

The ratios of lift and axial thrust to undeflected thrust of nozzle-deflection-plate configurations using the Coanda effect for obtaining jet deflection and lift were evaluated from force measureme...

The ratios of lift and axial thrust to undeflected thrust of nozzle-deflection-plate configurations using the Coanda effect for obtaining jet deflection and lift were evaluated from force measurements. Pressure distributions were also obtained over the surface of the deflection plate. The convergent nozzles used in the study were of rectangulsr cross section with exit heights ranging from 0.5 to 3.7 inches. The deflection surfaces were single flat plates from 1.37 to Il. 75 inches long. The nozzles discharged into quiescent air over a range of pressure ratios from 1.5 to 3.0.

In general, the performance of Coanda nozzles is substantially the same as that theoretically calculated for a flat-plate flap immersed in an airstream. For optimum performance, the ratios of lift to undeflected thrust were approtimately equal to the sine of the deflection angle; however, the maximum obtainable ratio was angle-limited, depending on nozzle height and pressure ratio.

For ratios of lift to undeflected thrust equal to theoretical values, pressures less than atmospheric existed over the entire surface of the deflection plate. An empirical relation was developed for predicting the required plate length in terms of the nozzle height for achieving optimum ratio of lift to undeflected thrust at a given deflection-plate angle and pressure ratio.

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