No abstract

not Available.

No abstract

No abstract

The definition of the pipe flow friction factor has been extended to include the effect of fluid viscoelastic properties on energy dissipation in turbulent tube flow. The resulting friction factor includes a characteristic fluid relaxation time, which can be determined directly from rheological measurements, and reduces to the usual Fanning friction factor for inelastic fluids. The use of this more general friction factor enables turbulent tube flow data for both fresh and shear degraded “concentrated” drag reducing polymer solutions of various concentrations in various tube sizes to be correlated by the usual f vs. NRe relation for Newtonian fluids in smooth tubes.

No abstract

the radius of curvature of the fringes is relatively large and the two types can exist simultaneously, it is easy to confuse the two. The error was not discovered until a large number of tedious hand measurements had been made.For wedge fringes, the fringes appear on a uniform wedge at positions where the thickness of the wedge is an integral multiple of the wavelength of the monochromatic light, that is since nk : 2~t cos r whenever the thickness has increased by k/2 from the last fringe, bright or dark, a new fringe appears, n is the order of interference, ~ the refractive index, t the thickness, and r the angle of incidence of the light. If r becomes a very little less than 90 ~ for thick wedges, Brewster's fringes result.Brewster's fringes are located at infinity and appear on the wedge as rings. The fringes will appear at positions governed by nk = ~t(cosine of the angle of refraction in the first glass flat minus cosine of the angle of refraction in the second glass flat) assuming cos r is about equal to 1, since the light passes only once through the cell.Variations in the refractive index of the wedge of electrolyte cause displacement of the fringes up and down the wedge (toward the apex if the change is an increase in concentration) which takes the form of a perturbation to the arc of the circle seen between the electrodes. The fringes measured for the S/V position were a 2 ~ 35' arc of a circle of 3.43 cm radius and those for the C/A position had a similar radius of cur-vature. A detailed account of how to relate wedge fringe perturbation to concentration has been given by O'Brien and Rosenfield (7) and complete review of the theory by O'Brien (9).To allow plots of concentration changes to be made on cartesian coordinates, these arcs had to be converted to straight lines. Frequently the increments at successive positions at which measurements were made were smaller than the expected precision of measurement. However, to ensure that some systematic method of correction for fringe curvature was used, a transparent plastic template whose plotting edge was cut in the mirror image of the curve was used in replotting the uncorrected values read from the display of the original fringes. In this way the curvature was plotted out and also any rotation of axis needed to correct the angle of the fringes to the electrode to 90 ~ . Of course since both the plastic template and the pencil point had thickness, a further, but it is thought, random scatter of points resulted. A smooth curve was then drawn through the points. A scale in which fringe perturbations are shown as concentration change in moles per liter has been added to the figures where necessary. The limit of accuracy of the measurements is that with which the center of any fringe can be located relative to the center of another fringe. In this case it is thought from the results of repeated measurements to be about • of a fringe width or about •x 10-41VL Details of this type of calculation have been given previously (4). ABSTRACTThe a-c impedance characte...

Electrochemical corrosion rates of Cu and Cu-Ni alloys have been measured in oxygenated 0.5M NaCI and in synthetic seawater using the Tafel extrapolation procedure. In addition, Cu corrosion has been measured with the linear polarization procedure. A rotating disk electrode system was used in the measurements with rotation rate varying from 500 to 6000 rpm. The corrosion characteristics of Cu and 90Cu-10Ni alloy in the two media, and 70Cu-30Ni alloy in 0.5M NaCI have been found to be similar. For these systems, the variation of corrosion current, corrosion potential, and anodic partial current with rotation rate of the electrode could be explained in terms of a convective diffusion controlled corrosion mechanism incorporating the generation of a soluble copper complex on the electrode surface. The 70-30 alloy in synthetic seawater behaved differently. Corrosion current, corrosion potential, and the anodic partial current were all constant with rotation rate, indicating a surface kinetic-controlled corrosion mechanism.Cu + 2CI -=CuCl2 -+ e kc (1)