A wing with flexible surface have possibly unique aerodynamic characteristics due to an interference in aerodynamic force. Particularly in slender parawing, a pair of separation vortex formed above the wing have an important effect upon the wing shape and at the same time, the wing shape affects the position and the strength of the vortex. In the present paper, the flow past a yawed slender parawing with and without leading-edge separation is considered by using the BROWN and MICHAEL's line vortex model and comparisons are made between them. As the result, it is shown that the position of the vortex with yaw angle affects largely the leading-edge gradient of the wing shape but it does not lead to a severe change of the normal force CN and the rolling moment Cl, except for an intermediate value of wing tension. And it is also shown that the values of CN and Cl in the separated flow are a few times larger than those in the attached flow for a certain range of wing tension.
Considering the lateral variation of eddy viscosity, a plane turbulent jet of an incompressible fluid is calculated. Approximating eddy viscosity as proportional to the lateral turbulence intensity and using simple functions like (u/u0)n or (1+ αηm)-1 to express distributions of measured turbulence intensity, fair agreement is obtained between the calculated and some experimental results of the mean velocity distributions with constants such as n=0.3 or α=0.13 and m=4. In addition, a simple empirical formula for mean velocity distribution is given, which is analogous to the formula derived for a far wake flow and is corrected in the exponent to fit the measured profile in the central region of the jet. A numerical table of u/u0 is presented comparing the known analytical solutions, empirical formulas and the present results.
The design, fabrication and evaluation of an ion engine simulator which is a dynamic electrical load model used for developing the ion propulsion system are described. Since an ion engine can not be operated without a vacuum test facility, the simulator is necessary instead of the engine for some development phases and it will also bring a benefit of reduced cost and time for developing the power conditioner. The simulator consists of a load unit and a simulation unit. The former includes load regulators of which the impedances are controlled electrically by the latter. A micro computer system is employed for the simulation unit, and it represents the dynamics of the engine in real or reduced time scale which are formulized mathematically by the thermal and plasma models. The parameters of models are identified by a large computer support system. The simulator is connected with a power conditioner and its performances are investigated. The distinctive features such as flexibility, accuracy, sufficient dynamic characteristics and wide range simulation are obtained by this approach.
It is a general practice to use a square as the structure section towers. However, there are towers with sections of equilateral triangle, rectangle, hexagonal triangle and others, depending on the purpose of their construction. Wind tunnel experimental data are scanty about the structure of the tower and neither the relationship is clear between the drag-coefficients and the projection ratios, which are essential for design. We investigated the relationship between the drag-coefficients and the projection ratios with towers of special section as well as the variation of drag-coefficient with wind direction. We revealed the following facts: In the case of special sections (equilateral triangle, rectangle, hexagonal triangle), the relationship between the wind direction and the drag-coefficient fitted the result of a square section when the drag-coefficient was calculated considering the projection area. Even with towers of special sections, the relationship between the projection ratio and the drag-coefficient can obviously be discussed in terms of three zones just as with towers of a square section.