This paper describes the analytical and experimental study of flow expansion due to resistance of a wire gauze placed in a parallel-sided channel. First, Taylor's source model was improved by introducing source-strength correction, and flow profiles and drag coefficients were calculated for various gauze heights. Next, measurements were also made on flow profiles and drag coefficients for resistance coefficients up to 20 in a smoke windtunnel. Consequently, agreement calculated and measured values was obtained. Furthermore, flow observation and velocity-distribution measurements were carried out for a model diffuser with high resistance coefficient wire gauze.
Two-dimensional generalization of a one-dimensional Petrov-Galerkin finite element shock capturing scheme is proposed. It is emphasized that the "preferred direction upwinding" is important in multi-dimensional applications. Scheme is developed for the two-dimensional Euler equations which stand for the invicid compressible flow problem. One, based upon characteristics, employs the Mach lines and streamline as preferred directions.
The Random-Choice-Method (RCM) was applied to a numerical simulation of a two-stage light-gas gun. The flow was assumed one dimensional and special procedure was employed at the section with area change. The pressure history at several points and the teminal velocity of the projectile are compared with experimental results at NAL TwoStage Light-Gas Gun. The results agreed very well with the experiments except that the numerical terminal velocities of the projective were 0 to 15% greater than experiments. The present method would become a useful tool in design and operation of such facilities.
Three subjects are studied for the vibration characteristics of laminated graphite-epoxy cylindrical shell. Firstly the eigen-value problem is exactly solved to obtain the natural frequency of layered composite cylindrical shell by use of Flugge type vibration equation. In the case of two layer crossply and angle-ply laminates the coupling effect decreases the fundamental natural frequency about 20%. For four layer antisymmetric cross-ply and angle-ply, the natural frequency is close to the one of the thickness-wise homogeneous cylindrical shell. However in the case of symmetric four layer crossply the lamination constitution unexpectedly affects the fundamental natural frequency. The natural frequency is explicitly obtained using Donnell type vibration equation of orthotropic cylindrical shell for the S2 boundary condition and the influence of lamination constitution is clarified. The optimum lamination constitutions for the highest fundamental natural frequency are disclosed. It is shown that the quasi-isotropic lamination is not optimal. The influence of lamination constitution on the nonlinear property of resonance curve for the fundamental natural frequency of the shell is analytically studied. It is concluded that the nonlinear property is softening for all laminations and the degree of the softening is stronger in the order of the circumferential layer alone, the ±45° angle-ply, the cross-ply, the quasi-isotropic and the axial alone.
The effect of nitramine addition on stable combustion of double-base propellants has been examined in order to lower the combustion limit of rocket motors. The nitramines tested in this study are RDX (cyclotrimethylene trinitramine) and HMX (cyclotetramethylene tetranitramine). These nitramines are used as the energetic materials to increase the specific impulse and are also used as the agents to decrease the burning rate of double-base propellants. It has been found that the addition of the nitramines acts to increase the heat of explosion at low pressures and to prevent an incomplete combustion of double-base propellants. Thus, the pressure exponent of the flame temperature decreases due to the increased flame temperature at low pressures. Consequently, the pressure of stable combustion limit of a double-base propellant rocket motor is lowered by the addition of nitramines.