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Table 5.3 Grain sizes, Gradation, Reynolds Number, and Settling Velocities of
Simulated Runoff Particles
The slurry flow rate into the mixing tank was considered to be constant over the
infilling portion of the test, even though drainage was by gravity. The average slurry flow
rate typically was 0.08 L/s and the bulk flow rates ranged from 1.6 to 4.4 L/s. Any
variations in the slurry flow rate were negligible compared to the sum of the bulk water
and slurry flow rates.
Approximately 190 L (50 gal) of the slurry were constantly mixed in the slurry
tank and drained into the rapid mixing tank during the filling portion of each test. The
suspended soils slurry and bulk water were mixed with a rotary paddle. The runoff
flowed through a baffle wall into the flume and down to the sediment control.
5.1.3 Sampling and Monitoring
Particle
Diameter,
mm
Percent
Smaller by
Weight
Reynolds
Number
Settling
Velocity,
mm/s
2000 100 41250 309
700 99 8541 183
360 93 3150 131
Newtonian Settling Ends 250 84 1823 109
Transition Begins 125 72 600 101
75 64 230 59
55 58 124 40
39 56 65 29
29 52 34 21
20 50 16 15
15 48 8 10
11 44 4 5.4
7.9 41 2 4.0
Transition Ends 5.7 37 1 2.3
Stokes Settling Begins 4.1 34 0.27 0.98
3.0 30 0.10 0.51
2.1 26 0.038 0.27
1.3 21 0.0079 0.09
0.9 20 0.0029 0.05
The resulting pool of runoff drained through the sediment control and the water
level in the flume upstream of the sediment controls was monitored with an ISCO
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