In the present paper, jet impingements of gas expanded through an orifice into a vacuum were numerically simulated by using the direct simulation Monte Carlo (DSMC) method. Three types of jet impingement, parallel, oblique and normal, were treated. The parallel and oblique impingements were considered as a three-dimensional problem, whereas normal impingement was treated as an axisymmetric problem. The numerical simulations were carried out using the variable soft sphere (VSS) model for nitrogen. For the energy exchange between translational and rotational modes, the Borgnakke-Larsen model was employed together with the temperature-dependent energy exchange probability of Boyd. Simulated results were compared with Legge’s experiments and a simple impingement model in the range of the reservoir pressures from 0.1×104 to 1.6×104 Pa. The present results agreed well with Legge’s experimental data of pressure and shear stress distributions on a flat plate.
A cell-splitting method for Cartesian grid generation that has the capability of taking into account the cases of thin body and sharp edge is proposed in this paper. Such cases are frequently found when solving the flow around a very thin wing, such as that of a supersonic transport (SST). The method has also been extended to treat the problem of multiple solid regions within a cell, which is sometimes encountered at a highly curved body surface. Validation of the method proposed here is carried out on a sharp, thin double wedge in a supersonic flow, where significant improvements in accuracy are achieved at the cost of a small increase in the number of cells. Furthermore, application of the present method to a model of SST shows its effectiveness on a three-dimensional, realistic geometry. As a result of making a pseudo-planar approximation for body surface elements, the total number of body surface elements was reduced by a factor of about 3.2 in this application. Local grid refinement by relocating grid cells to a curved surface is also proposed, so that a more accurate solution is obtained with a reasonable number of cells.
This paper studies the attitude control problem of a class of data relay satellite which has a large mobile antenna for tracking target spacecraft in low orbit. The movement of the antenna disturbs the satellite attitude motion through dynamic coupling of the motions of the antenna and the satellite main body. In the operation, control of the spacecraft attitude must be maintained even when the antenna rotates at a high angular velocity. In this paper, we apply robust gain-scheduled controller synthesis to this problem. The controller is designed as a robust stabilizing controller based on the H∞ controller synthesis of linear parameter varying system. The capability of the method is investigated by a numerical study.
A simple arcjet operation model has been developed based on a steady-state, quasi-one-dimensional discharge/flow analysis. An operation point is determined from a voltage minimum criterion. Both high and low-voltage mode solutions are obtained. In the high mode, the discharge current is attached to the anode in the supersonic flow region. The voltage-current characteristic exhibits a favorable decreasing dependence. In the low mode, the energy input from Joule heating is done effectively in the subsonic flow region. Plural solutions which correspond to the respective modes can coexist.
The importance of development of a rover to confirm directly the existence of ice on the lunar polar region is discussed. For a rover working in the shadowed area in the bottom of a crater, a power-supply system using a laser beam from the edge of the crater is proposed. A small system model is fabricated to demonstrate that the system can be realized.