Experiments in Fluids

, Volume 34, Issue 6, pp 662–677 | Cite as

Turbulence quantification and sediment resuspension in an oscillating grid chamber

Original

Abstract

An oscillating grid chamber has been developed to study sediment suspension, desorption of compounds from the resuspended sediment, and air–water mass transfer. The chamber is designed to allow researchers to study desorption of contaminants from cohesive sediments and the flux of those contaminants to the vapor phase. The chamber uses a single vertically oscillating grid driven by a DC motor and closed-loop controller. Sediment to be studied is placed in the bottom of the chamber and entrained into the water column by the turbulence generated by the oscillating grid. A two-component laser Doppler velocimeter (LDV) was used to measure the turbulent velocity field inside the chamber. Detailed mapping of the turbulent kinetic energy (TKE) produced by this grid arrangement was compared with established grid-stirred systems. At distances closer to the grid than two grid bar spacings, large lateral gradients exist in the TKE. The suspension of cohesive sediments was also studied using this chamber. Steady-state suspended sediment concentrations were achieved within 30 min for a variety of turbulence levels. By adjusting the grid operating parameters, the TKE can be set to simulate the turbulence found either at the bed or free surface in open-channel flow systems. With some care, the oscillating grid chamber can be used as a simple laboratory analogue to study various environmental processes within the flow or at either the sediment–water or air–water interface.

List of symbols

C1, C2

, C2constants

f

grid oscillation frequency (T-1)

g

gravitational constant (LT-2)

h

depth of open-channel flow (L)

M

spacing between bars in oscillating grid (L)

S

grid stroke length (L)

SEGL

slope of energy grade line in open-channel flow (m/m)

TKE

total kinetic energy of turbulence (L2T-2)

TSS

total suspended solids concentration (ML-3)

U

bed shear velocity (LT-1)

U, V

instantaneous horizontal velocities (LT-1)

W

instantaneous vertical velocities (LT-1)

\( \overline U , \overline V ,\overline W \)

mean velocities (LT-1)

u, v, w

instantaneous velocity fluctuations (LT-1)

u′, v′, w

root mean square (rms) turbulent velocity fluctuations (LT-1)

\( \overline {uw} \)

Reynolds stress (L2T-2)

y

vertical distance from bed in open-channel flow (L)

z

vertical distance from grid (L)

α

constant

κ

Von Karman constant

ν

kinematic viscosity (L2T-1)

Π

Cole's wake parameter

R

Reynolds number based on shear velocity and flow depth, Uh/ν

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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  1. 1.Department of Civil and Environmental EngineeringRowan UniversityGlassboroUSA
  2. 2.St. Anthony Falls Laboratory, Department of Civil EngineeringUniversity of MinnesotaMinneapolisUSA

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