On the spreading of non-canonical thermals from direct numerical simulations

Liu, K.; Zgheib, Nadim; Balachandar, S.

doi:10.1063/1.5138981

Cited by 11 publications

(1 citation statement)

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“…It is well known that elliptical jets exhibit different rates of entrainment in the two transverse directions due to differing rates of shear thickening along the initial minor and major axes of the ellipse. 44,45 In fact, such non-canonical spreading is also present in buoyancy driven flows such as thermals 46 and gravity currents, 47–49 albeit due to different mechanisms.…”

Section: Evolution Of the Puffmentioning

confidence: 99%

Investigation of theoretical scaling laws using large eddy simulations for airborne spreading of viral contagion from sneezing and coughing

et al. 2021

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Using a set of large eddy point-particle simulations, we explore the fluid dynamics of an ejected puff resulting from a cough/sneeze. The ejection contains over 61 000 potentially virus-laden droplets at an injection Reynolds number of about 46 000, comparable to an actual cough/sneeze. We observe that global puff properties, such as centroid, puff volume, momentum, and buoyancy vary little across realizations. Other properties, such as maximum extent, shape, and edge velocity of the puff, may exhibit substantial variation. In many realizations, a portion of the puff splits off and advances along a random direction, while keeping airborne droplet nuclei afloat. This peeled-off portion provides a mechanism for virus-laden droplets to travel over large distances in a short amount of time. We also observe that the vast majority of droplets remain suspended within the puff after all liquid has evaporated. The main objectives of the study are to (i) evaluate assumptions of Balachandar's et al. theory [Int. J. Multiphase Flow 132 , 103439 (2020)], which include buoyancy effects, shape of the puff, and droplet evaporation rate, (ii) obtain values of closure parameters, which include location and time of the virtual origin, and puff entrainment and drag coefficients, and (iii) evaluate the accuracy of the theory in predicting the shape, size, and location of the puff, as well as droplet number density long after ejection. The theory adequately predicts global puff properties including size, velocity, and distance traveled, the largest size of droplets that exit the puff due to settling, and the droplet size distribution within the puff long after ejection.

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Section: Evolution Of the Puffmentioning

confidence: 99%