China
Africa
Explore chapters and articles related to this topic
Surface Failure
Published in Ansel C. Ugural, Youngjin Chung, Errol A. Ugural, Mechanical Engineering Design, 2020
Ansel C. Ugural, Youngjin Chung, Errol A. Ugural
High relative velocities between solid parts and liquid particles can produce cavitation of the liquid, which may destroy the surface of the part. Bubbles are produced if the liquid pressure drops lower than its vapor pressure. Cavitation ordinarily takes place on ship propellers, turbine blades, and centrifugal pumps. Damage caused by cavitation to metal surfaces is mechanical. But in corrosive surroundings, cavitation can often damage protective oxide films on the surface that appears to be roughened with closely spaced pits. In severe situations, enough material is taken off that the surface has a spongy texture. Cast stainless steel, cast magnesium bronze, cast steel, bronze, cast iron, and aluminum are frequently used to reduce the cavitation [4]. The most effective way to deal with cavitation damage is generally to increase the surface hardness.
Fundamentals of Treating the Interface
Published in Mukai Kusuhiro, Matsushita Taishi, Interfacial Physical Chemistry of High-Temperature Melts, 2019
Mukai Kusuhiro, Matsushita Taishi
A gas dispersion system in a liquid phase is a bubble, which is more finely classified into bubble, foam, and dispersed gas. The bubble is an independent particle comprising a gas phase existing in a liquid phase or surrounded by thin liquid films. The difference between dispersed gas and foam is shown in Table 2.2,34 including the examples at room temperature, based on the references. The fundamental difference between the two is that each bubble in the dispersed gas system is independent and that the viscosity of the dispersion medium plays a major role in the transfer of the dispersed gas, while bubbles in the foam system become a polyhedron structure insulated by thin films, and the behavior of the bubbles is dominated by the property of the thin films. Therefore, when an external force is applied, for example, the form system becomes unstable due to the collapse of the thin films, while the dispersed gas system ends up being stable because of the micronization of the bubbles.
Introduction to Boiling
Published in Gautam Biswas, Amaresh Dalal, Vijay K. Dhir, Fundamentals of Convective Heat Transfer, 2019
Gautam Biswas, Amaresh Dalal, Vijay K. Dhir
where θ is the angular position measured from the forward stagnation point. Since surface tension contribution for a large bubble is small, the static pressure inside and outside the bubble can be considered to be equal. The pressure at a point A inside the bubble can be written as () pA=p0+ρvgΔH
Gas injection test of remolded saturated soil with consolidation
Published in Marine Georesources & Geotechnology, 2021
Yiping Zhang, Yongjin Chen, Huabin Lv, Mengxian Hu, Yongchao Zhou
Besides gas migration mechanism, the effects of bubble growth and migration on the physical and mechanical properties of soil include: (1) significant changes to theoretical and measured values of the undrained modulus and Young’s modulus for soil which contain large gas bubbles(Johnson et al. 2002; Sobkowicz and Morgenstern 1984; Wheeler and Gardner 1989); (2) reduction in the permeability coefficient for the gassy soil as gas bubbles content increases (Sakaguchi, Nishimura, and Kato 2005); (3) the acceleration of vertical deformation of an embankment constructed on peat due to the migration of gas bubbles (Acharya, Hendry, and Martin 2017); and (4) the delayed accelerated deformation of the gas-charged soil during the gas release (Wang et al. 2018).
Challenging soft computing optimization approaches in modeling complex hydraulic phenomenon of aeration process
Published in ISH Journal of Hydraulic Engineering, 2021
Amin Mahdavi-Meymand, Miklas Scholz, Mohammad Zounemat-Kermani
Cavitation within a hydraulic structure is defined as formation of vapor cavities in water. Bubbles are formed when the static pressure of the liquid drops below its vapor pressure (Kramer et al. 2006) and are swept downstream, where pressure is higher and the bubbles implode. Collapsing bubbles appear over a very short time and cause pressure fluctuations close to the spillway surface (Volkart and Rutschmann 1984). This instantaneous pressure can cause fatigue and subversion of spillway material, and continued material removal can cause significant damage (Kells and Smith 1991). Figure 1 provides an example of a spillway collapse due to the cavitation in the chute spillway of Oroville dam in California in 2017.