Turbulence in the flow was initially modeled using the κ-ε model and turbulent intensities
of 10% were assigned to the inlets. Since the κ-ε solution in this geometry is symmetric with
respect to YZ and XZ planes, only one quarter of the geometry was introduced to the FLUENT
software. Also, since the transport properties of air are strongly dependent on temperature, this
dependence was manually assigned in FLUENT. The flow was then solved with second-order
solvers and numerical results were obtained with residual levels below 10-5%. Some of these
results are presented in Figure 3.10 for a mass-flow-rate of 1.23×10-2 kg/s: Figure 3.10 shows
pressure and velocity contours in a cross section of the gun, parallel to the jet. The pressure
contours clearly illustrate that most of the pressure drop occurs in the nozzle region and, that
pressure is almost constant upstream of the contact-tips. Gas velocity and temperature are also
observed to be approximately constant upstream of the contact-tips. Hence, there is no need to
include this region in the numerical domain, as only the shear stresses on the wire-tips are of
concern to this study.