International Shipbuilding Progress - Volume 14, issue 152

Authors: Lopes Jr., L.A.

Article Type: Research Article

DOI: 10.3233/ISP-1967-1415201

Citation: International Shipbuilding Progress, vol. 14, no. 152, pp. 129-133, 1967

Authors: Walsh, Myles

Article Type: Research Article

DOI: 10.3233/ISP-1967-1415202

Citation: International Shipbuilding Progress, vol. 14, no. 152, pp. 134-139, 1967

Authors: Sanders, James V.

Article Type: Research Article

Abstract: The hydrodynamic properties of polymer solutions were studies by measuring the terminal velocities of steel spheres dropped in aqueous solutions of poly(ethylene oxide). Polymers used were WSR 301, WSR 205, WSR 35, and N 3000. Concentrations ranged from 10 weight parts per million to 2%. Sphere diameters ranged from 0.038 in. to 1.000 in. When the flow is characterized by a fully developed wake, significant drag reduction is obtained with the same polymers that are known to reduce turbulent skin friction and maximum drag reduction is achieved using minute amounts of polymer (100 ppm for WSR 301). It is postulated …that the polymer reduces the diameter of the wake by delaying the separation of the laminar boundary layer. Under laminar flow conditions, the spheres exhibit a dual terminal-velocity. This behavior is explained by assuming that the fluid can exist in one of two different structures and the structure which exists when the fluid is at rest becomes unstable when a critical shear stress is exceeded. Calculations of this critical shear stress are in agreement with the value found for a similar transformation observed in viscometer measurements. The polymer solution studied can be described by means of a modified viscosity which depends only on the concentration and on whether the flow is associated with the fast or slow terminal velocity. Using this dual viscosity, a plot of drag coefficient vs Reynolds number results in a single curve for each type of polymer. This curve follows the Stokes solution to a higher Reynolds number than does the curve for a Newtonian fluid, The Reynolds number where the polymer leaves the Stokes solution moves to lower values as the molecular weight of the polymer decreases. Each curve approaches the same value of the drag coefficient at the higher Reynolds numbers. Only those polymers that have a dual viscosity have the ability to reduce drag. Show more

DOI: 10.3233/ISP-1967-1415203

Citation: International Shipbuilding Progress, vol. 14, no. 152, pp. 140-157, 1967

Authors: Jackley, Donald N.

Article Type: Research Article

Abstract: To determine whether drag reduction is the result of turbulence dampening per se, the decay characteristic of a free turbulent jet was investigated. The work was suggested by recent boundary-layer studies showing that fluid drag reduction is caused by the presence of high-molecular-weight polymers in solution. The jet, having all the properties associated with turbulence except those caused by the presence of a wall, provided an ideal tool for the experiment. It was found that in a water solution of drag-reducing polymer, shear stress was reduced in the nozzle but not in the free jet. Drag reduction was therefore concluded …to be a phenomenon of the wall because the character of the turbulence that is beyond the influence of the wall resembles the character of the turbulence in a free jet, which was found to be unaffected by the drag-reducing agent. Show more

DOI: 10.3233/ISP-1967-1415204

Citation: International Shipbuilding Progress, vol. 14, no. 152, pp. 158-165, 1967

Authors: Levy, Joseph | Davis, Sydney

Article Type: Research Article

Abstract: Drag measurements were made by towing a thin plate (a plate with a 3-ft chord) in plain water and in dilute solutions of Polyox WSR-301, over a Reynolds-number range between 3 × 10 6 and 1 × 10 7 . These tests were performed in Aerojet’s ring channel. Samples of these solutions were also tested in a pipe-friction apparatus at the U.S. Naval Ordnance Test Station, Pasadena. Results of the test with the plate show a reduction in drag of 33% with a Polyox concentration of 1.5 wppm, …and a maximum reduction of 63% with concentrations of 15 to 20 wppm. With higher concentrations (up to 100 wppm), the drag reduction was somewhat less than this maximum. There is evidence that the effectiveness of these solutions for reducing drag was diminished with passage of time after preparation of the solutions. Also, it appeared that there was some instability in the flow over the plate. Show more

DOI: 10.3233/ISP-1967-1415205

Citation: International Shipbuilding Progress, vol. 14, no. 152, pp. 166-175, 1967