The pressure distributions on the surface of a circular cylinder rotating in a uniform flow were measured near the critical Reynolds number in a low speed wind tunnel. In the subcritical region, when the spin parameter is increased, the average pressure coefficient on the side of the higher relative velocity decreases suddenly at the critical spin parameter, so that the lift force decreases from the maximum to the minimum value. The separation point on this side oscillates violently downstream and upstream. With further increase in the spin parameter, the separation point moves downstream. The pressure distribution in every one rotation varies so randomly near the critical spin parameter that the average lift force decreases continuously to the minimum value. In the supercritical region, the average pressure coefficient on the side of the lower relative velocity increases suddenly at the critical spin parameter, and the separation point on this side moves suddenly to the upstream direction. The movement of the separation point is more rapid than in the case of the subcritical region. As the result, the lift force decreases discontinuously from the maximum to the minimum value.
Instead of the conventional conical nose projectiles, quasi-two-dimensional (Q2D) projectiles were accelerated in a cylindrical ram accelerator. The Q2D projectile has a wedge-shaped tip creating a quasi-two-dimensional flowfield when it flies in the ram accelerator. Methane based combustible gas mixture was filled in a 8m long ram acceleration tube at 2.5MPa. A good acceleration over 6, 000g has been achieved. The present study was the first try to apply a non-conical nose projectile in the ram accelerator experiment. It will be helpful in the development and operation of a two-dimensional facility in which a two-dimensional flowfield is formed and hence easily visualized by optical techniques.
A preliminary study is presented to realize an idea to optimize the shape of an airfoil section in accordance with airplane flight conditions, deforming it elastically by internal pressure control. Here is calculated by analytical method rather than by finite element method the shape of an airfoil section after deformed largely as an elastic thin shell by applying internal pressure. In the analysis are treated the two types of airfoil sections; a symmetric airfoil section and a cambered airfoil section. In the former case, the good agreement is obtained between the analytical results and the experimental results. Moreover, it is confirmed that this method can be applied to any cylindrical shells with a uniform section besides airfoil sections, if the ordinate of the initial shape is expressed in a polynomial of the abscissa.