Balanced flap type supersonic control surfaces

• Main Author: Heimer, Harry J.
• Format: Others
• Published: 1958
• Online Access: https://thesis.library.caltech.edu/4353/1/Heimer_hj_1958.pdf; Heimer, Harry J. (1958) Balanced flap type supersonic control surfaces. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/YVYN-ZD39. https://resolver.caltech.edu/CaltechETD:etd-11012004-142134 <https://resolver.caltech.edu/CaltechETD:etd-11012004-142134>

The purpose of this investigation is to qualitatively explain the flow phenomena which occur on a balanced flap type control surface at supersonic speeds and to find means of calculating the pressure distributions occurring. The popular and generally useful linearized flow theory, and in fact any inviscid theory, cannot be used since viscosity plays a predominant part in the determination of the flow. It is shown that the flow often involves shock induced separation and reflection of shock waves by these separated wakes. Experimental data in the form of pressure distributions and shadowgraph pictures of the flow are used to arrive at a description of the flow. By use of the empirical results given, a method of predicting the pressure distributions for this type of surface is derived. This procedure is then used to calculate several pressure distributions which are compared with those experimentally determined. The separation effects that occur at the larger angles of attack and/or control surface deflection angles cause the control effectiveness and hinge moments to be very non-linear. It is shown that the use of a gap between the wing and control surface delays or eliminates separation depending on the size of the gap used. Data are presented for a typical control surface, in which the hinge moments were reduced by a factor of 8 or 10 by using a gap between the wing and control surface. A method is given for estimating the size gap necessary to achieve this reduction.