Investigation Of Control Surface Hinge Moment Characteristic At Low Speed

Control surface hinge moment is very important to airplane design and flight control, and also the experiment of hinge moment measurements is an important part of low speed wind tunnel tests. In order to choose the appropriate balance for hinge moment measurements, computation of hinge moment is done with CFD software. There are many factors to impact the control surface hinge moment, and in this paper some of these factors are researched, such as the width of the gap between the stabilizer and the control surface, the wind speed, the trip strips for boundary layer transition at different location on the stabilizer surface, and also the hinge moment characteristic of split rudder is studied, then the experimental and computational results are compared in order to offer reference for wind tunnel tests.In this paper there are five chapters, and the content of each chapter is as follow.In the foreword of this paper, it contains the background of hinge moment research, research actuality at home and abroad, research content and methods in this paper. The hinge moment can be measured directly by hinge moment balance in wind tunnel tests, so the results are credible, but there are some disadvantages such as long periods, difficult technique, determining the full-scale values of the balance, and so on. Also the hinge moment can be gained with CFD software. And in this way the details of flow field can be obtained at more model conditions in short periods, but the results have a little larger error. In this paper the hinge moment characteristic and the effects of some factors are researched via wind tunnel tests and numerical simulation with CFD software.The second chapter introduces the hinge moment experiments in the 1.4m×1.4m low speed wind tunnel in CARDC-L. In the experiments the hinge moment is measured directly with strain gauge balance. From the experiments the gap effect, wind speed effect, transition effect, the hinge moment characteristic of split rudder and flow visualization using oil stream is investigated. Then the correction of the results is done according to the classic method.In the third chapter the process of CFD software simulation is shown. In the numerical computation, the model for numerical computation is accomplished with the CAD software SolidWorks, and is imported into ICEM-CFD to generate C-shaped structural grids. Then numerical simulation of the hinge moment is going on after importing the grids and setting control parameters, and when the calculation is finished, results are exported with the format .res, and also the results can be exported with other format as .cgns. Then post processing is done in CFX-Post using the results with the format .res, and in Tecplot using the results with the format .cgns. The simulation contains gap effect, wind speed effect, the hinge moment characteristic of split rudder.Research results and analysis of the hinge moment is in the fourth chapter. From the simulation using CFX the range of the control surface hinge moment is gained, according to which a hinge moment balance is chosen with appropriate full-scale values. In order to research the control surface hinge moment characteristic, the experimental and computational results are compared and analyzed. After the comparison between the experimental and computational results at different width of the gaps, the distribution of pressure and streamlines around the control surface are gotten to learn the reason of gap effect. From the experimental and computational results, it indicates that the change of the wind speed influences slightly upon the hinge moment. Then comparison is done between experimental and computational results of the split rudder, to find the aerodynamic characteristic of the split rudder, and to check the dependability of 2D simulation. Based on the experimental results, it is found that fixed boundary layer transition on model surface can be achieved by sticking trip strips at different location on the stabilizer surface, and it influences the control surface hinge moment to a certain extent. By using oil stream, an intuitive understanding of flow field around the control surface is present. And the flow pattern from computer aided flow visualization is consistent with what oil stream shows, so the reasonability of computation results is further confirmed.At the last chapter the conclusion about the work in this paper is shown.