Cavitation Suppression and Stress Effects in High-Speed Flows of Water With Dilute Macromolecule Additives

Experiments were carried out to study the effect of dilute aqueous polymer solutions on flow-generated cavitation inception. The cavitation inception on 1/4 and 1/2-in-dia models with a hemispherical nose in a blowdown water tunnel was definitely inhibited at Reynolds numbers from 7 × 10⁴ to 3.1 × 10⁵. Reduction of the incipient cavitation number to 30 percent of its value for tap water was observed, depending on the kind of polymer used, its concentration, and the Reynolds number. Flow velocity field visualization was achieved by optical techniques, which measured the flow velocities and was used to correct values computed from venturi pressure drop. For guar gum (300 ppm) tests, the computed velocities were approximately 8 percent low.