Fluid-Dynamic Consideration of Bottom Materials

by Hormoz Pazwash, (A.M.ASCE), Asst. Prof.; Fac. of Civ. Engrg., Tehran Univ., Tehran, Iran,
James M. Robertson, (F.ASCE), Prof. of Theoretical and Appl. Mech.; Univ. of Illinois at Urbana-Champaign, Urbana, IL,

Serial Information: Journal of the Hydraulics Division, 1971, Vol. 97, Issue 9, Pg. 1317-1329

Document Type: Journal Paper


Bottom materials often involve clay-water suspensions which evidence complex rheology. Studies of the non-Newtonian behavior of kaolin are reported herein. Concentric viscometer analysis at concentrations of 5, 10 and 20% by weight indicate Bingham-plastic-body behavior; Newtonian fluid behavior is evidenced at low concentration and alkalinity. The dependence of the fluid properties, yield stress, and plastic viscosity on pH and concentration is characterized; both these properties increase with increase in concentration, or decrease in pH (increase in acidity). Measurements of the drag of simple bodies in this mixture are reported. The drag coefficient of spheres and discs in the laminar boundary-layer region (Reynolds numbers below 2 x 105) indicate negligible non-Newtonian effect above a Reynolds number of 1,000. At lower Reynolds number, a yield stress effect is superimposed. The dependence of this effect on the Hedstrom number is indicated for values of this parameter up to 4,000. The occurrences with spheres and discs are found to be much the same.

Subject Headings: Reynolds number | Fluid dynamics | Plasticity | Yield stress | pH | Spheres | Kaolin | Measuring instruments

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