Hydrodynamic experiments on dacryoconarid shell telescoping

0429385 - GLÚ 2015 RIV NO eng J - Journal Article
Hladil, Jindřich - Šimčík, Miroslav - Růžička, Marek - Kulaviak, Lukáš - Lisý, Pavel
Hydrodynamic experiments on dacryoconarid shell telescoping.
Lethaia. Roč. 47, č. 3 (2014), s. 376-396. ISSN 0024-1164. E-ISSN 1502-3931
R&D Projects: GA ČR GAP210/10/2351
Institutional support: RVO:67985831 ; RVO:67985858
Keywords : dacryoconarid shells * experimental fluid mechanics * narrow cones * Palaeozoic * telescoping
Subject RIV: DB - Geology ; Mineralogy; CI - Industrial Chemistry, Chemical Engineering (UCHP-M)
Impact factor: 1.454, year: 2014

It is not uncommon that small conical dacryoconarid shells are found inserted one into another. Although this phenomenon has been studied for decades, and interparticle collisions in turbulent flows have largely considered to be responsible, no satisfactory explanation has been provided. We performed experiments under laboratory conditions using narrow aluminium cones as replicas of these shells. Two different flow regimes were tested to mimic the probable hydrodynamic conditions in the ocean. First, large-scale rhythmic back and forth coherent motion of water over the seabed was reproduced in an oscillating sloshing tank (sloshing mode). Second, small-scale irregular stirring motion in turbulent bulk was imitated in cylindrical containers placed into a shaker (mixing mode). With sloshing, a high production of irreversibly telescoped cones was present in clear water and at driving frequencies comparable to the upper limits known for sea waves. With shaking, both coalescence and break-up of the cones were observed, as the quasi-random hydrodynamic forces generated by vigorous liquid motion were roughly comparable with the mechanical forces holding the cones together. However, the stability of the clusters of telescoped cones in the shaker could be enhanced with the addition of fine solid particles (suspended silt). In addition, a simple mathematical model was suggested for the flow interaction with a submerged conical particle in the case of the sloshing mode, providing an interesting insight into the evolution of strong deceleration zones
Permanent Link: http://hdl.handle.net/11104/0234571