Numerical simulation of gas jet in liquid crossflow with high mean jet to crossflow velocity ratio

Breakup Processes and Droplet Characteristics of Liquid Jets Injected into Low-Speed Air Crossflow

The breakup processes and droplet characteristics of a liquid jet injected into a low-speed air crossflow in the finite space were experimentally investigated. The liquid jet breakup processes were recorded by high-speed photography, and phase-Doppler anemometry (PDA) was employed to measure the droplet sizes and droplet velocities. Through the instantaneous image observation, the liquid jet breakup mode could be divided into bump breakup, arcade breakup and bag breakup modes, and the experimental regime map of primary breakup processes was summarized. The transition boundaries between different breakup modes were found. The gas Weber number (Weg) could be considered as the most sensitive dimensionless parameter for the breakup mode. There was a Weg transition point, and droplet size distribution was able to change from the oblique-I-type to the C-type with an increase in Weg. The liquid jet Weber number (Wej) had little effect on droplet size distribution, and droplet size was in the range of 50–150 μm. If Weg > 7.55, the atomization efficiency would be very considerable. Droplet velocity increased significantly with an increase in Weg of the air crossflow, but the change in droplet velocity was not obvious with the increase in Wej. Weg had a decisive effect on the droplet velocity distribution in the outlet section of test tube.

Bubbly flow in degassing cyclones and potential applications

A degassing cyclone is a separator that is widely used for the removal of bubbles and dissolved gas from liquids. Gas bubbles move toward the swirling center region in a degassing cyclone due to centrifugal force. The dissolved gas is desorbed due to a decrease in the saturated solubility resulting from the pressure gradient in the degassing cyclone. Additional carrier gas bubbles with lower partial pressure lead to mass transfer at the turbulent bubble interface. The final state of the dissolved gas and carrier gas bubble in degassing cyclones is an important issue that can be used to develop a theoretical foundation for green separation engineering. The feasible development of this technology and potential applications are discussed in this work.

Using a Dynamic and Constant Mesh in Numerical Simulation of the Free-Rising Bubble

A two-phase bubbly flow is often found in the process industry. For the efficient operation of such devices, it is important to know the details of the flow. The paper presents a numerical simulation of the rising bubble in a stagnant liquid column. The interFOAM solver from the open source Computational Fluid Dynamics (CFD) toolbox OpenFOAM was used to obtain the necessary data. The constant and dynamic computational grids were used in the numerical simulation. The results of the calculation were compared with the measured values. As expected, by using the dynamic mesh, the bubble trajectory was closer to the experimental results due to the more detailed description of the gas–liquid interface.