Viscoplastic dam breaks and the Bostwick consistometer
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In this article, the authors present a theoretical and experimental analysis of the dam break of a viscoplastic fluid in a horizontal channel, using a shallow, slow fluid model based on the Herschel-Bulkley constitutive law to characterize the early and late stages of flow, the final state and the dependence on yield stress and nonlinear viscosity.Abstract:
We present a theoretical and experimental analysis of the dam break of a viscoplastic fluid in a horizontal channel. A shallow, slow fluid model based on the Herschel-Bulkley constitutive law allows one to characterize the early and late stages of the flow, the final state and the dependence on yield stress and nonlinear viscosity. A particular diagnostic is advanced (time ratios based on the length of time required for the fluid to slump certain distances from the broken dam) that may assist an experimentalist to unravel those dependences. Experiments are conducted with cornsyrup, and aqueous suspensions of xanthan gum, kaolin, carbopol, cornstarch and apple puree. Cornsyrup xanthan gum and kaolin show fair quantitative agreement with theory. Carbopol compares less favourably, due primarily to inertial effects which are missing from the theory. The results for cornstarch confirm that it is shear thickening, but its detailed rheology remains unknown (and unexplored). Apple puree also appears to compare well with theory, although repeating the dam break in a roughened channel leads to substantially different results, suggesting that fluid separation can induce effective wall slip (a problem that also probably plagues the Bostwick device). Finally, theory is compared with Bostwick tests with fruit puree, with limited success.read more
Citations
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References
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The propagation of two-dimensional and axisymmetric viscous gravity currents over a rigid horizontal surface
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Viscosity bifurcation in thixotropic, yielding fluids
TL;DR: In this paper, it was shown from inclined plane tests, intended to determine the yield stress, that these systems in fact exhibit peculiar properties: they stop flowing abruptly below a critical stress, and start flowing at a high velocity beyond a critical value, which in addition increases with the time of preliminary rest.
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A method for the spatial discretization of parabolic equations in one space variable
Robert D. Skeel,Martin Berzins +1 more
TL;DR: In this article, a spatial discretization method for polar and nonpolar parabolic equations in one space variable is proposed, which is suitable for use in a library program.