China 
Africa 
Explore chapters and articles related to this topic
Applied Chemistry and Physics
Published in Robert A. Burke, Applied Chemistry and Physics, 2020
Secondary effects of an explosion are shock-wave modification, fire and shock-wave transfer. There are three ways that a shock wave can be modified: it may be reflected, focused or shielded. Reflection refers to the shock wave striking a solid surface and bouncing off. When a shock wave strikes a concave (curved) surface, the force of the shock wave is focused, or concentrated, on an object or small area once it bounces off the concave surface. This effect is similar to the principle behind satellite dishes. When a signal reaches a satellite dish from the satellite in space, the signal is focused on the electronic sensor protruding out of the front of the satellite dish. Shielding simply means that the shock wave encounters an object too substantial to be damaged by the wave, so the shock wave goes around the object or is absorbed by it. The area immediately behind the object provides a place of shelter from the shock wave. Fire and shock-wave transfer involves the transfer of the shock-wave energy and fire to other objects, causing fires and destruction.
Governing Equations of Fluid Mechanics and Heat Transfer
Published in Dale A. Anderson, John C. Tannehill, Richard H. Pletcher, Munipalli Ramakanth, Vijaya Shankar, Computational Fluid Mechanics and Heat Transfer, 2020
Dale A. Anderson, John C. Tannehill, Richard H. Pletcher, Munipalli Ramakanth, Vijaya Shankar
A shock wave is a very thin region in a supersonic flow, across which there is a large variation in the flow properties. Because these variations occur in such a short distance, viscosity and heat conductivity play dominant roles in the structure of the shock wave. However, unless one is interested in studying the structure of the shock wave, it is usually possible to consider the shock wave to be infinitesimally thin (i.e., a mathematical discontinuity) and use the Euler equations to determine the changes in flow properties across the shock wave. For example, let us consider the case of a stationary straight shock wave oriented perpendicular to the flow direction (i.e., a normal shock). The flow is in the positive x direction, and the conditions upstream of the shock wave are designated with a subscript 1, while the conditions downstream are designated with a subscript 2. Since a shock wave is a weak solution to the hyperbolic Euler equations, we can apply the theory of weak solutions, described in Section 4.4, to Equation 5.205. For the present discontinuity, this gives [E]=0
Supersonic Waves
Published in Rose G. Davies, Aerodynamics Principles for Air Transport Pilots, 2020
The air properties after an oblique shockwave are very important to lift, drag, and the stability of flight control of a supersonic aircraft, and the design of effective jet engines, rockets, and other airspace objects at supersonic speeds.
Computationally efficient GPU based NS solver for two dimensional high-speed inviscid and viscous compressible flows
Published in Engineering Applications of Computational Fluid Mechanics, 2023
Muhammad Naveed Akhtar, Kamran Rasheed Qureshi, Muhammad Hanif Durad, Anila Usman, Syed Muhammad Mohsin, Band Shahab, Amirhosein Mosavi
Computational fluid dynamics (CFD) is the study of gas or fluid flow through software modelling of the underlying physics. The Navier-Stokes (NS) equation is the basic equation for CFD, which describes the relationship between pressure, velocity, density, and temperature for fluids in motion (Chandar et al., 2013). Another important factor for fluids moving at high velocity is the occurrence of shock waves in the flow field (Hoffmann & Chiang, 2000). A shock wave is generated when the fluid, gas, or plasma is flowing faster than the speed of sound. When a shock wave is generated, an almost discontinuous change in the temperature, density, and pressure of the fluid is observed. When modelling and simulating fluid flow at higher velocities, it is important to consider such parameters (Hoffmann & Chiang, 2000).
An Experimental and Kinetic Study of Phenylacetylene Ignition at High Temperatures
Published in Combustion Science and Technology, 2023
Tao Ding, Weixin Tang, Rui Wang, Ping Xu, Dongxian Li, Changhua Zhang
During the experiment, the velocity of the incident shock wave was measured using four piezoelectric pressure sensors (PCB 113B) installed on the side wall of the last 1 m of the driven section. The velocity of the incident shock wave at the end wall was calculated using the linear extrapolation method. The one-dimension normal-shock model of Chemkin-Pro software (ANSYS chemkin V.17.0) was used to calculate the temperature and pressure after the reflected shock wave. A quartz optical fiber was installed at the same cross-section of the last pressure transducer, which was located 15 mm away from the end-wall of the shock tube. The optical signal during ignition was detected by the quartz optical fiber and then fed into a grating monochromator. The output of the monochromator was set at 431 nm and coupled with a photomultiplier to capture the CH* emission signal, which was then displayed on a digital phosphor oscilloscope.
The influence of flexible/rigid obstacle on flame propagation and blast injuries risk in gas explosion
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Shuwei Yu, Yulong Duan, Fengying Long, Hailin Jia, Jun Huang, Yunbing Bu, Lul Zheng, Xiaohua Fan
The reflected shock wave between the flame front and the obstacle forms a positive feedback mechanism with turbulent combustion, which is one of the reasons for the acceleration of the flame in the later stage of the obstacle. In Figure 9, after the flame passes through the obstacle, different vortex degrees appear on the flame front, which promotes the reaction intensity. In contrast, the obstacle reflects the shock wave in the same direction as the flame front, which accelerates the reaction speed between the vortex center and the flame front and further promotes the growth of the surface area of the flame front. In the case of flexible obstacles, the shock wave causes the elastic deformation of the obstacles, and the obstacles absorb part of the shock wave. The acceleration effect of the reflected pressure wave on the flame front caused by the deformation is smaller than that of rigid obstacles. The absorption of shock waves by flexible obstacles plays a positive role in reducing the indirect and direct damage caused by reflected shock waves.