REASSESSMENT OF THE WALL EFFECT OF NON-NEWTONIAN FLUID FLOW.
Technical rept. 1 Feb 66-1 May 68,
RENSSELAER POLYTECHNIC INST TROY N Y DEPT OF MECHANICS
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Because of several previous reports of flow anomalies in the laminar capillary flow of macromolecular solutions, and the general friction reduction activity in turbulent flow, an experiment was devised to check directly the proposed slip interpretation of such anomalies. The test system consisted of a two-dimensional flow channel, having a uniform width of 1.5 inches, and, alternatively, an adjustable convergent taper. Dilute aqueous solutions of the polymers Carbopol, Natrosol, and Polyox were recirculated in steady laminar flow from a large reservoir. During the tests, velocities, pressures, and wall shear stresses were measured. Local velocities were obtained by the local injection of conductive tracer fluid, whose passage was sensed by sets of electrodes stationed along the flow. Wall shear stresses were measured on a small, freely displacable, traction surface flush with the channel wall. The tests covered concentrations of Carbopol of 0.1 to 0.4, Natrosol of 0.5 to 1 and Polyox of 0.5 to 1. Approximate viscosities ranged from about 10 to 1000 centipoise. Wall shear rates up to 1000sec were attained. The results are in good agreement with the established viscometric properties of the tested materials. Actual shear stresses agree with those calculated from pressure drops, and velocities exhibit no detectable anomaly near the wall. Author
- Fluid Mechanics