D.H. Lammlein PhD Dissertation - Vanderbilt University

Figure 27: Model prediction (top left) without the threading vertical velocity effect, (top
right) without the vertical or the radial scrolling velocity effect, (bottom) with both
vertical and radial velocity effects imposed, figure from [65].
The authors present these macrographs as evidence for the necessity of a 3D
thermo-fluid model (as opposed to 2D) which includes some accounting for feature
effects. It is noted that the model that does not include imposed velocity fields to account
for feature effects results in the simulated longitudinal marker material being deposited in
a simple linear fashion, similar to its pre-welded position.
Atharifar, Lin and Kovacevic [67] use Fluent CFD software to identify the
occurrence of a downstream stagnation point. The downstream stagnation point has been
indicated by Shinoda [68] as the likely point of initiation of the tunnel-like defect in
FSW.
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