The composition and ultimate principle of airshooting experimental system were expounded, and the mechanism of airshooting was emphatically discussed on the basis of experiments. The results indicate that the fracture...The composition and ultimate principle of airshooting experimental system were expounded, and the mechanism of airshooting was emphatically discussed on the basis of experiments. The results indicate that the fracture of medium under airshooting resultes from both shock action of air spray and quasi static dilatation of high pressure air. The action of air spray leads to the initial fracture of the wall of borehole and arouses stress wave to propagate in the medium. The quasi static dilatation of high pressure air results in the propagation of initial fractures and produces shear fracture in the medium along the free boundary. Along the direction of minimum burden, the superposition of quasi static and dynamic stress fields can prompt the propagation of cracks. The superposition of the reflected wave, which comes from multiple free surfaces, will result in the fracture of medium also if multiple free boundaries exist.展开更多
In order to clarify the mechanism by which aerodynamic noise is generated from separated flow around an airfoil blade,the relation between the attack angle and the aerodynamic noise of the blade was analyzed using a w...In order to clarify the mechanism by which aerodynamic noise is generated from separated flow around an airfoil blade,the relation between the attack angle and the aerodynamic noise of the blade was analyzed using a wind tunnel experiment and a CFD code.In the case of rear surface separation,the separated vortex which has a large-scale structure in the direction of the blade chord is transformed into a structure that concentrates at the trailing edge with an increase in the attack angle.The aerodynamic noise level then becomes small according to the vortex scale in the blade chord.When the flow is separated at the leading edge,a separated vortex of low pressure is formed at the vicinity of the trailing edge.The pressure fluctuations on the blade surface at the vicinity of the trailing edge become large due to the vortex in the wake.It is considered that the aerodynamic noise level increases when the flow is separated at the leading edge because the separated vortex is causing the fluctuations due to wake vortex shedding.展开更多
文摘The composition and ultimate principle of airshooting experimental system were expounded, and the mechanism of airshooting was emphatically discussed on the basis of experiments. The results indicate that the fracture of medium under airshooting resultes from both shock action of air spray and quasi static dilatation of high pressure air. The action of air spray leads to the initial fracture of the wall of borehole and arouses stress wave to propagate in the medium. The quasi static dilatation of high pressure air results in the propagation of initial fractures and produces shear fracture in the medium along the free boundary. Along the direction of minimum burden, the superposition of quasi static and dynamic stress fields can prompt the propagation of cracks. The superposition of the reflected wave, which comes from multiple free surfaces, will result in the fracture of medium also if multiple free boundaries exist.
文摘In order to clarify the mechanism by which aerodynamic noise is generated from separated flow around an airfoil blade,the relation between the attack angle and the aerodynamic noise of the blade was analyzed using a wind tunnel experiment and a CFD code.In the case of rear surface separation,the separated vortex which has a large-scale structure in the direction of the blade chord is transformed into a structure that concentrates at the trailing edge with an increase in the attack angle.The aerodynamic noise level then becomes small according to the vortex scale in the blade chord.When the flow is separated at the leading edge,a separated vortex of low pressure is formed at the vicinity of the trailing edge.The pressure fluctuations on the blade surface at the vicinity of the trailing edge become large due to the vortex in the wake.It is considered that the aerodynamic noise level increases when the flow is separated at the leading edge because the separated vortex is causing the fluctuations due to wake vortex shedding.
