The Importance Of Instantaneous Flow Structures To Total Mixing And Reaction Of Gamete Filaments In Broadcast Spawning
Shoaei, Farrokh 1 ; Soltys, Michael A. 2 ; Crimaldi, John P. 3
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One of the most common methods of reproduction in the sea is broadcast spawning, wherein marine invertebrates release eggs and sperm into the ambient flow and fertilization occurs externally. Gamete coalescence at large scales is dominated by fluid stirring, and may be influenced by the presence of flow obstructions (e.g., coral heads, bed topography). The effect of the turbulent wake behind a round obstacle on the second-order reaction between two initially distant scalars has been investigated by series of planar laser-induced fluorescence experiments. The scalars are released continuously, and are separated from each other by a lateral distance that initially impedes the reaction. The direct effect of the wake on mixing enhancement is determined by comparing segregation parameter for cases with and without the cylinder obstruction. A decomposition of the total reaction into mean and instantaneous contributions reveals that as turbulence bring filaments together mean processes underestimate fertilization as filaments coalesce in concentrations orders of magnitudes above the mean concentrations. This study shows that the presence of an obstacle in spawning regions may substantially raise the contribution of instantaneous processes up to 65%.