Description

Project Description(Water Spraying Considering Breakup and Evaporation Using Discrete Phase Model (DPM)), ANSYS Fluent Tutorial

In this project, we aim to simulate the water spraying from a nozzle considering the breakup of droplets and evaporation using the Discrete Phase Model (DPM) and Species Transport model. It can be claimed that this simulation is the most accurate spraying procedure modeling which considers all details.

Methodology: Water Spraying DPM simulation

The 2 mm diameter water droplets are injected with 1.25 m/s velocity from the nozzle. The environment is warmer than the droplets, so when the temperature of the droplet reaches 282.5K, evaporation takes place. In addition, stochastic collision & coalescence, and droplet breakup are considered by using the Taylor analogy breakup model (TAB).

In the spraying process, the droplets are distorted and their shape doesn’t remain spherical. On the other hand, the drag coefficient strongly depends on droplet shape. Thus, dynamic-drag drag law and Discrete Random Walk Model are used. Furthermore, the floor has a Wall-film DPM boundary condition leading to film formation instead of terminating trajectory calculations.

Conclusion (Water spraying DPM simulation)

As mentioned in the previous section, the injection starts with a 1.25 m/s velocity. Due to consecutive collisions of the droplets, some of them break up and some of them join each other (accumulation). It is crystal clear in diameter distribution contour as shown below. Although the initial diameter is 2mm, the range is between 0.002mm and 7mm.

When the droplets reach the floor surface, their trajectory calculation doesn`t terminate. They can stick, rebound, spread or splash depending on the impact energy ( This is fully described in the DPM boundary condition article). The animations and contours can help understanding better.