In the low-speed wind tmnel testing for a twodimensional wing model, a correction to the angle of incidence is considered due to the non-uniform spanwise distribution of lift. This phenomenon is concemed with the change of the effective angle of incidence, which results from the interference between the wing tip and the tunnel wall perpendicular to the wing span. Since the change of the effective angle of incidence is connected with the induced drag according to the lifting-line wing theory, the change of the effective angle of incidence may be estimated if the induced drag could be determined by experiment. In this study, the induced drag is obtained by the difference between the total drag measured by the wind tunnel balance and the profile drag determined by the wake measurements. The result with this correction to the angle of incidence is in good agreement with reliable experimental data.
A numerical method is presented for the prediction of unsteady loadings on lifting airfoils that are due to oscillations of trailing edge control surfaces in subsonic compressible flow. An asymptotic pressure distribution is used to remove and separately evaluate the singularity in the kinematic downwash distribution. The method gives accurate result, quick convergence and excellent computational efficiency to other current methods.
For the purpose of numerical analysis of threedimensional compressible steady flow around an airplane, it is necessary to find quantitatively local positions of an out surface of the airplane and local directions of the surface in a rectangular computational grid system in physical space. The out surface of airplane is made up of many elements of small triangular planes. The local positions of the out surface in the grid system are determined by local intersections of axes of the grid with these triangular planes. Directions of the triangular planes are substituted for the local directions of the out surfaces. Using these results, views of the out surface of airplane are drawn in sheets of paper.
The shear field theory had been widely used to analyze the reinforced shell structures. In this theory, the joints of the reinforcement are assumed to be pinned joints and external forces are generally applied to the joints. However, using the finite element method (FEM), the stress calculation for the reinforced shell structures would be possible without the assumption of pinned joints. First of all, it is verified that the agreement between the results by means of FEM and the experimental ones are very good. Next, the stress distribution of the reinforced plate are not uniform in the plate. It is also stated that, by comparing the maximum principal stress σλ max with the maximum shearing Stress τmax, we obtained the result σλ max/τmax_??_1.50 from our experiments and calculations.
Long extendible spacecraft boom subjected to solar radiant heating is modeled as a thin-walled long cylinder of split non-overlapping section. Tip mass is attached to one end which is free to warp and other is fixed. The boom is heated by the unidirectional solar radiation assumed to be normal to its longitudinal axis. The equation of thermallyinduced torsional vibration of this system is formulated by considering the coupling effect of mechanical and thermal phenomena as one-degreeof-freedom system. The characteristic equation is evaluated using the Routh-Hurwitz stability criterion and it is found that the stability characteristics are dependent upon, along with three system parameters, the direction of radiant heating. The boundary curves, which divide the parameter plane into regions of stability and instability according to a direction of radiation, and some typical responses based on the closed-form solution are also included.
The forces acting on the bodies in a twodimensional, incompressible, inviscid and timedependent flow are formulated. The flow field may contain vortices which are arbitrarily situated. The total impulse acting on the bodies in a certain time interval is calculated by applying the momentum theorem to a control surface which encloses the bodies and all vortices and moves with the fluid. The force is obtained by taking the time average of the total impulse. It is shown that in the case of a single body the forces can be calculated by using the state of the flow field only at the beginning and the end of the time interval. The formula is applied to calculations of the forces acting on the body in the unsteady flow which is calculated by the discrete vortex method.