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A fluid dynamics study of seawater flow through Gelidium nudifrons 1
Author(s) -
Anderson S. Miles,
Charters A. C.
Publication year - 1982
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1982.27.3.0399
Subject(s) - turbulence , thallus , flow (mathematics) , seawater , mechanics , chemistry , physics , environmental science , geology , oceanography , botany , biology
Gelidium nudifrons, growing in the subtidal region of semiexposed coasts has a thallus composed of rodlike branches which are closely spaced, but the structure is sufficiently open so that water flows freely through it. The turbulence of the water before and after passing through the plant was measured by hot‐film anemometry in a water tunnel in the laboratory and observed by a dye stream technique in the tunnel and in situ in the sea. The flow after passing through the plant was smooth at velocities up to a critical value, but turbulent for velocities above an abrupt transition. Turbulence in the flow entering the plant did not change this result. Analysis of the results demonstrates that the plant strongly suppresses turbulence in the flow entering its thallus and at the same time generates microturbulence of its own at velocities above critical values varying from 6 to 12 cm·s −1 , depending on the diameters and spatial density of the branches, due to the formation of systematic vorticity in the wakes of the individual branches. The transition in the flow induced by the branches of a marine plant is probably a phenomenon of considerable adaptive significance, because the turbulence generated by the plant itself or by neighboring plants may be the only turbulence in water motion past the plant that is of the right scale to enhance nutrient uptakes and effect the exchange of gases and solutes.