El académico e investigador del CEGA, Dr.Jacobus Le Roux, pone a disposición la planilla “Settling Velocity Calculator”

Monday, 26 de September

Como parte de su trabajo recientemente publicado en el Journal of Volcanology and Geothermal Research, “Fall velocity of multi-shaped clasts”, el Dr. Le Roux entrega la herramienta que puede descargarse del siguiente link: http://goo.gl/TMRX6x

“Fall velocity of multi-shaped clasts” – Journal of Volcanology and Geothermal Research 289 (2014) 130–139
Accurate settling velocity predictions of differently shaped micro- or macroclasts are required in many branches
of science and engineering. Here, a single, dimensionally correct equation is presented that yields a significant improvement on previous settling formulas for a wide range of clast shapes. For smooth or irregular clasts with
known axial dimensions, a partially polynomial equation based on the logarithmic values of dimensionless
sizes and settling velocities is presented, in which the values of only one coefficient and one exponent need to
be adapted for different shapes, irrespective of the Reynolds number. For irregular, natural clasts with unknown
axial dimensions, a polynomial equation of the same form is applied, but with different coefficients. Comparison
of the predicted and measured settling velocities of 8 different shape classes as well as natural grains with unknown axial dimensions in liquids, representing a total of 390 experimental data points, shows a mean percentage
error of −0.83% and a combined R2 value of 0.998. The settling data of 169 differently shaped particles of
pumice, glass and feldspar falling in air were also analyzed, which demonstrates that the proposed equation is
also valid for these conditions. Two additional shape classes were identified in the latter data set, although the
resultant equations are less accurate than for liquids. An Excel spreadsheet is provided to facilitate the calculation of fall velocities for grains settling individually and in groups, or alternatively to determine the equivalent sieve size from the settling velocity, which can be used to calibrate settling tubes.