CFD Simulation of Particle Acceleration in an AWJ Cutting Head

Computational Fluid Dynamics (CFD) has become a preferred development tool for engineering problems associated with fluid dynamics. Cui* used a commercial CFD package Fluent6.2.1 to study the abrasive acceleration within an abrasive waterjet cutting head. Here are the highlights.

A multiphase mixture model was first used to model the turbulence of a water-air two phase flow. Abrasive particles were then introduced into the two-phase flow using a discrete phase model to study the particle motion and trajectory.

The diagram above is a schematic of a typical abrasive waterjet cutting head. The diagram below shows the velocity vector of the two-phase (water and air) flow. Two vortexes are indicated. The first vortex is located between the orifice and the abrasive inlet, on the opposite side of the abrasive inlet. It revolves clockwise. It is also found that pressure in vortex I is below atmosphere. Vortex II is located below and near the abrasive inlet. It is much larger and revolves counter-clockwise.

The diagram below shows thetrajectory of a particle after it is introduced into the two phase flow. Itshows that the particle first travels upstream, hitting the bottom of the orifice,and then collides with the mixing tube wall twice before exiting.

* Cui, L. (2006) Study on abrasive particle acceleration in the mixing tube of abrasive water jet based on the CFD models, Proceedings of the 8^th Pacific Rim International Conference on Water Jet Technology, Oct. 10-12, 2006, Qingdao, China, Paper 10.