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A Numerical Model of Bubbling Thermoplastics

A Numerical Model of Bubbling Thermoplastics

A Numerical Model of Bubbling Thermoplastics

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Bubble Migration<br />

• Driven by gravity, temperature gradients<br />

(surface tension, viscosity dependence on T)<br />

U<br />

=<br />

−<br />

2<br />

2(<br />

ρ p − ρ g ) gR ⎡ ⎛ d ln µ ⎞ R ⎛ d lnσ<br />

⎞⎤<br />

∂T<br />

+ ⎢2RR&<br />

⎜−<br />

⎟ + ⎜−<br />

⎟<br />

9µ<br />

dT<br />

dT<br />

⎥<br />

⎣ ⎝ ⎠ 3µ<br />

⎝ ⎠⎦<br />

∂z<br />

• Wake effects<br />

• Bubbles slow as approach surface

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