Experimental Study

Deposited sediment from the pond was collected at a number of sampling stations within the wet pond using an Ekman dredge and combined to form a composite sample. The sample and a large volume (500 l) of pond water were brought to the Hydraulics Laboratory of the National Water Research Institute in Burlington, Ontario, Canada and were tested in the Rotating Circular Flume. Use of the pond water as the suspending medium preserved the chemical and biological characteristics of the sediment-water mixture in the laboratory experiments.

8.3.1 Rotating Circular Flume

A sectional view of the rotating circular flume is shown in Figure 8.2. The flume is supported by a rotating platform, which is 7.0 m in diameter. The flume is 5.0 m in diameter at the centre-line, 30 cm wide, and 30 cm deep. The annular top cover fits inside the flume with close tolerance. The gap between the edges of the top cover and the flume walls is about a millimeter. The height of the cover inside the channel can be adjusted by raising or lowering the top cover. The flume and the cover are rotated in opposite directions. The maximum rotational speed of both components is three revolutions per minute. The flume is equipped with a Laser Doppler Anemometer to measure the flow field and a Malvern Particle size analyzer to measure the size distribution of sediment flocs in suspension. The Malvern Particle size analyzer was placed directly underneath the flume, and the sampling cell of the instrument was connected to a short sampling tube that was inserted through the bottom plate of the flume into the flow. The sample was drawn through the sampling cell continuously

^ LDj ^ ball bearing

FIGURE 8.2 A sectional view of the rotating circular flume used in the experimental study.

10T.Cap. Jackscrew

Annular top plate support

Annular top plate Annular channel

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