Propagation Of Expansion Waves Research Articles

On the Generation of an Intense Temperature Gradient Through a Modified Shock Tube Hydrodynamics for a Possible Continuous Sterilization Process

Abstract Data on hydrodynamics of carbon dioxide in shock tube can be presented as a main opportunity to apprehend and establish sterilization treatment process. Here, a modified and axi-symmetric shock-tube model has been developed to simulate shockwave propagation and reflection after rapid bursting of two diaphragms separated initially with a relaxed fluid. It has been demonstrated that the given model is capable of accurately simulating, locating, and measuring shock and expansion wave propagation and reflections as well as estimating the thermodynamic preconditions that can lead to prompt sterilization.

Numerical Investigation of Aerodynamic Drag and Pressure Waves in Hyperloop Systems

Hyperloop is a new, alternative, very high-speed mode of transport wherein Hyperloop pods (or capsules) transport cargo and passengers at very high speeds in a near-vacuum tube. Such high-speed operations, however, cause a large aerodynamic drag. This study investigates the effects of pod speed, blockage ratio (BR), tube pressure, and pod length on the drag and drag coefficient of a Hyperloop. To study the compressibility of air when the pod is operating in a tube, the effect of pressure waves in terms of propagation speed and magnitude are investigated based on normal shockwave theories. To represent the pod motion and propagation of pressure waves, unsteady simulation using the moving-mesh method was applied under the sheer stress transport k–ω turbulence model. Numerical simulations were performed for different pod speeds from 100 to 350 m/s. The results indicate that the drag coefficient increases with increase in BR, pod speed, and pod length. In the Hyperloop system, the compression wave propagation speed is much higher than the speed of sound and the expansion wave propagation speed that experiences values around the speed of sound.

Expansion Wave Propagation into a Cavity

Expansion Wave Propagation into a Cavity

Evolution of weak waves and central expansion waves in a non-ideal relaxing gas

Abstract The main features of small amplitude waves generated by a planar piston-like surface in a planar flow of a vibrationally non-ideal relaxing gas are investigated. It is found that the analytical solution of the flow field for weak waves and central expansion wave propagation is influenced by the relaxation time and van der Waals excluded volume.

Unsteady turbulence in expansion waves in rivers and estuaries: an experimental study

A sudden decrease in water depth, called a negative surge or expansion wave, is characterised by a gentle change in free-surface elevation. Some geophysical applications include the ebb tide flow in macro-tidal estuaries, the rundown of swash waters and the retreating waters after maximum tsunami runup in a river channel. The upstream propagation of expansion waves against an initially steady flow was investigated in laboratory under controlled flow conditions including detailed free-surface velocity and Reynolds stress measurements. Both non-intrusive free-surface measurements and intrusive velocity measurements were conducted for relatively large Reynolds numbers with two types of bed roughness. The data showed that the propagation of expansion waves appeared to be a relatively smooth lowering to the water surface. The wave leading edge celerity data showed a characteristic trend, with a rapid acceleration immediately following the surge generation, followed by a deceleration of the leading edge surge towards an asymptotical value: $$(\mathrm{U}+\mathrm{V}_\mathrm{o})/(\mathrm{g}\times \mathrm{d}_\mathrm{o})^{1/2}=1$$ for both smooth and rough bed experiments. The results indicated that the bed roughness had little to no effect, within the experimental flow conditions. Relatively large fluctuations in free-surface elevation, velocity and turbulent shear stress were recorded beneath the leading edge of the negative surge for all flow conditions. The instantaneous turbulent shear stress levels were significantly larger than the critical shear stress for sediment erosion. The present results implied a substantial bed erosion during an expansion wave motion.

A study of the rapid depressurization of hot water and the dynamics of vapour bubble generation in superheated water

Liquid can be brought to a superheated state by means of very rapid depressurization. Such situations are typical for pipe rupture accidents, which can occur in processing equipment and have to be taken into account, for example, in the design of nuclear power plants with water-cooled reactors. An experimental investigation was carried out using a horizontal pipe attached to a pressure vessel. Rapid depressurization was achieved with the use of a rupture disc assembly. The paper describes the most important test results, a method for calculating the pressure undershoot below the saturation pressure and a simplified model of expansion wave propagation with vapour bubble generation in superheated liquid. On the basis of this model, the density of nucleation sites and the evolution of pressure and void fraction in the two-phase mixture can be estimated.

The dynamic problems of thermal elasticity

We examine the stresses which arise in an elastic half-space when the surface of the latter is suddenly heated, bearing in mind the rates of expansion-wave propagation in an elastic medium and the finite rate of heat propagation.