New Zealand Journal of Marine and Freshwater Research abstracts
A submersible device for measuring drag forces on aquatic plants and other
organisms
Fraser M. Callaghan1
Glenn G. Cooper1
Vladimir I. Nikora2
Nicolas Lamouroux3
Bernhard Statzner4
Pierre Sagnes4
John Radford5
Emmanuel Malet4
Barry J.F. Biggs1
1 National Institute of Water and Atmospheric
Research Limited
P.O. Box 8602
Christchurch, New Zealand
email: fraser.callaghan@ltnt.iet.mavt.ethz.ch
2 University of Aberdeen
Scotland, United Kingdom
3 Cemagref
UR Biologie des Ecosystèmes Aquatiques
Lyon, France
4 CNRS-Ecologie des Hydrosystèmes Fluviaux
Université Lyon 1
69622 Villeurbanne Cedex, France
5 Zebra-Tech Limited
Nelson, New Zealand
Abstract This paper describes a device, the submersible
drag gauge (SDG), that can be used for drag measurements in studies of flow-biota
interactions at low (setup A) and high (setup B) load applications. The device
is designed so that solely drag forces acting on a test object in a boundary
layer flow are measured. The SDG can measure drag on organism(s), such as macrophtyes,
crayfish or mussels, as well as a combination of such organisms and sediments
assembled in a variety of arrangements in both laboratory and field conditions.
Laboratory calibrations over the range of 0 to 4 N showed that setup A registered
forces as low as 0.02 N, whereas setup B often did not register forces up to
c. 0.15 N. The relative standard error of drag measurements was <3% for forces >0.2
N (setup A) or <4% for forces >1 N (setup B). Using a rigid cylinder, and
natural and artificial (plastic) Egeria densa as examples, showed how
the SDG can serve in studies of flow-biota interactions such as drag-velocity
relations, assessments of drag coefficients, or the frequency spectrum of macrophyte
drag.
Keywords drag gauge; plant dynamics; flow-biota interactions;
boundary layer flow; experimental flume
New Zealand Journal of Marine and Freshwater Research, 2007, Vol. 41:
119–127
0028–8330/07/4101–0119 © The Royal Society
of New Zealand 2007
M06038; Online publication date 9 March 2007. Received 6 July 2006;
accepted 22 November 2006
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