Quality
Waterjet Newsletter – 05/13/2008
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.
Abrasive Inlet Vortex I Vortex II
The diagram below shows the
trajectory of a particle after it is introduced into the two phase flow. It
shows 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 8th Pacific
Rim International Conference on Water Jet Technology, Oct. 10-12, 2006,
Qingdao, China, Paper 10. |
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