This paper involves studies on fields of flow and mixing with fuel injection in the combustor region of a Scramjet engine. The numerical simulations are performed by solving the full two-dimensional Navier-Stokes equations using the explicit TVD scheme. The main theme of this paper is to investigate the mechanism how the injected hydrogen is mixed with air in the supersonic flow. First, the problem is examined when the k-ε equations are applied to the flow field with the injection. The results show that the standard coefficients are inadequate and the wall function cannot be used. But without the function, the k-ε equations become so unstable. Therefore the q-ω equations are used which are more stable near the wall. Second, the influences are examined when the pressure wave exists in the flow field with injection. The results show that the expansion wave has the effect to promote mixing, on the other hand the oblique shock wave has the effect to obstruct mixing.
This work involves studies on the effects of the methods of injection on mixing fields of hydrogen in the free stream. The numerical simulations are performed by solving the full two-dimensional Reynolds averaged Navier-Stokes equations. As the injection methods, single injection, tandem injection, and parallel injection are examined. In single injection, the injection angle is varied, in tandem injection, the distance and mass flow ratio of the two injections is varied, and in parallel injection, the distance between the wall and the injection is varied. The total injection mass flow is constant in all cases. Each method of injection is evaluated by the correlation between the mixing efficiency and the mass flow averaged total pressure loss. The results show that the mixing efficiency in parallel injection is two times as much as in other methods of injection. So it can be said that the perpendicular momentum of injected hydrogen hardly gives effects on mixing in a two-dimensional flow.
In this report, the techniques of successive approximation of the multiple regression analysis are discussed, and are applied to the estimation of aerodynamic derivatives from flight test data by the equation error method. One of the techniques converts a multi-variate problem into the combination of two-variate problems with respect to each explanatory variable. The other technique converts a multi-variate problem into a three-variate problem, which uses a variable and its estimation value as two explanatory variables. The former is usefull for the simple iterative calculation, and the latter is convenient for understanding about the effect of multicollinearity. As the both techniques can be easily visualized, they are usefull to understand the processes and the physical relations from the data to the estimated results through our eyes.
This paper describes the second electric discharge method for visualizing three dimensional shock shapes around hypersonic vehicles. The method is based on the following ideas: When an electrical discharge is generated across a shock wave, the shock wave can be seen as a different radiation intensity in the electric discharge. Therefore, the three-dimensional shock shape can be visualized by taking a discharge photograph from the downstream side of the flow. In this paper, the reasons that the different radiation intensity occurs are mentioned qualitatively by considering the electric field distribution near the shock wave. As an example of this method, the shock shape around a delta winged semicone is visualized.
A general form of boundary element method for incompressible flow has been developed using Green's function. An integral equation of the perturbation velocity potential is obtained. On the paneldivided surfaces, this results in a set of linear algebraic equations. The pressure distribution on complete aircrafts including wing, body, and tail can be found using present method. Two examples of fuselage design problem for low drag are presented, in which the frictional drag is approximated with the local velocity and the surface area. Flexible modification of fuselage shape is obtained by using spline surfaces. One of the examples shows a practical application of the method for flow separation prediction.