Weight Criterion on Flow Control in Level Flight

摘要

To achieve a reduction of the power required for level flight, a generic weight criterion is given that can be used in the design and evaluation of a practical flow control system. Two cases are investigated for drag reduction by normal injection. In case 1, in which injection air comes from inlets, an increase in the ram drag overweighs the skin friction drag reduction and the weight criterion cannot be satisfied. In case 2, in which suction near the rear portion of a fuselage provides injection air for skin friction drag reduction, the weight criterion is given in an analytical expression, depending on a number of the parameters such as the mean aircraft weight, relative control system weight, pressure difference, injection area ratio, and control power density ratio. To overcome the weight penalty, the net benefit of drag reduction is more easily achieved for a sufficiently large aircraft. This approach can be similarly applied to other flow control techniques such as synthetic jet and plasma actuator, as long as the functional relationship between the control objectives (e.g., drag reduction and lift enhancement) and relevant parameters is known.