Numerical Simulation of Water Jet Flow Using Diffusion Flux Mixture Model

A multidimensional diffusion flux mixture model was developed to simulate water jet two-phase flows. Through the modification of the gravity using the gradients of the mixture velocity, the centrifugal force on the water droplets was able to be considered. The slip velocities between the continuous phase (gas) and the dispersed phase (water droplets) were able to be calculated through multidimensional diffusion flux velocities based on the modified multidimensional drift flux model. Through the numerical simulations, comparing with the experiments and the simulations of traditional algebraic slip mixture model on the water mist spray, the model was validated. 1. Introduction Liquid spray systems are widely used in many chemical, petrochemical, and biochemical industries, such as absorption, oxidation, hydrogenation, coal liquefaction, and aerobic fermentation. The operation of these systems is preferred because of the simple construction, ease of maintenance, and low operating costs. When the spray is injected from nozzle, it causes a turbulent stream to enable an optimum phase exchange. It is built in numerous forms of construction. The mixing is done by the liquid droplets and it requires less energy than mechanical stirring. A good understanding of the liquid droplet dynamics of the spray will help the engineers to design the high efficient facilities under optimized operating parameters. Although the operation of spray system is simple, due to the complexity of the two-phase turbulent flow, the actual physical flow phenomena are still lacking complete understanding of the fluid dynamics [1]. Many experimental facilities and methods were introduced to study the multiphase flows in spray systems. Ruck and Makiola [2] used a laser Doppler anemometer (LDA) to study the gas-oil droplet passing over a backward facing step. Ferrand et al. [3] used a phase Doppler and laser induced fluorescence technique to study the gas-droplet turbulent velocity and two-phase interaction through a jet with partly responsive droplets. Esposito et al. [4] used a monochrome charge-coupled device CCD camera to study the growth of the droplets. The experimental methods can provide very useful information about the liquid droplets at certain measurement points, but it is difficult for them to show the details of the flow fields and parameters inside the spray. Following the development of computer technology, it is already allowed to use the numerical method to do the researches in the recent decades [5]. Therefore, many researchers employ the numerical method, called