Browsing by Author "Lamb, Owen P."
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Item Air Entrainment in Flowing Water(St. Anthony Falls Hydraulic Laboratory, 1949-08) Lamb, Owen P.The physical entrainment of a gas by a liquid and the flow of gas-liquid mixtures are phenomena commonly encountered in engineering practice, but avoided or arbitrarily compensated for in theoretical considerations and in design analysis. The progress toward a satisfactory explanation of these phenomena has been hampered by a lack of accurate experimental observations of entrained flows and by the complexity of the theoretical analysis when certain of the physical forces can no longer be neglected.Item An Electrical Method for Measuring Air Concentration in Flowing Air-Water Mixtures(St. Anthony Falls Hydraulic Laboratory, 1950-03) Lamb, Owen P.; Killen, John M.An electrical instrument has been developed to measure the air concentration in flowing air-water mixtures as part of an investigation of the mechanism by which atmospheric air is entrained in flowing water. The theory, development, and verification of this instrument are described in this report. The instrument is shown in Figs. 6c and 7, and the electrical circuit is shown in Fig. 9b. The electrical measurement of air concentration was chosen after examining possible mechanical, chemical, and magnetic methods. The method consists basically of a measurement of the difference between the conductivity of a mixture of air and water and conductivity of water alone. A mechanical strut supporting a pair of electrical probes has been combined with the electrical circuit in such a manner that air-concentration measurements may be made, not at a point, but at least in a small region of the flow. With this instrument it is now possible to traverse the flow cross section both vertically and laterally and to obtain the distribution of air in the flowing mixture. The relation between the instrument readings and air-concentration values are determined theoretically and the instrument is direct reading. by checking the results of the electrical method against a direct mechanical sampling method, it has been determined that the values of air concentration computed form theoretical conditions alone were sufficiently accurate for experimental work without further calibration. The instrument is now designed for application in an experimental laboratory channel, but with the use of a more rugged strut and supporting structure the method could be applied equally well in large flumes and spillways.Item Model Experiments for the Design of a Sixty Inch Water Tunnel Part V(St. Anthony Falls Hydraulic Laboratory, 1948-09) Holdhusen, James S.; Lamb, Owen P.A study of vaned elbows was made at the St. Anthony Falls Hydraulic Laboratory as part of the research program for the design of the proposed 60-in. water tunnel of the David Taylor Model Basin, Bureau of Ships, Department of the Navy. The shape, size, and spacing of the vanes to be used in the elbows were determined from the work of previous investigators, and model studies of the vane cascade were performed at the Laboratory as part of a broad research program in fluid flow diversion. Additional model studies of the assembled elbow were performed on a 1:10 scale model of the 6o-in. tunnel. From the model studies on the vane cascade, the optimum angular setting of the vanes was obtained, as well as data regarding pressure distribution and energy loss. The validity of the application of model results to a prototype was examined in the additional studies on the elbows in the model water tunnel. On the basis of this study, a cascade of vanes of the proportions shown in Fig. 44 of this report is recommended for use in the prototype tunnel. The vanes are to be used at a spacing-chord ratio of 0.48 and a stagger angle of 99 to 101 degrees. The miter line is to cross each vane at about 37 1/2 per cent of the chord from the leading edge. Structural analysis of these vanes indicates that they may be of either solid or hollow cross section without detrimental effects on stresses, deflections, or vibrations. The studies also indicate that the vaned elbows in the prototype tunnel will be free from cavitation.Item Velocity Measurement of Air-Water Mixtures(St. Anthony Falls Hydraulic Laboratory, 1952-03) Straub, Lorenz G.; Killen, John M.; Lamb, Owen P.A troublesome aspect of experimental studies of flow phenomena in air-water mixtures has long been that of making accurate velocity measurements. In the pas, bulk-flow measurements have been made variously with surface floats, injected dyes or salt clouds, and relationships between the discharge and depth of flow. Point measurements of velocity have been attempted by measuring stagnation pressures in the air-water mixture. These methods have not been of sufficient accuracy for many purposes. An instrument for making accurate point velocity measurements throughout a section of an aerated flow stream has been invented and developed at the St. Anthony Falls Hydraulic Laboratory. The transit time, between two fixed electrodes, of minute cloudlets of salt solution injected repetitively into the flowing air-water mixture is measured electronically. A rate of 15 injections per sec permits a direct measure of the mean flow velocity over a short stream filament. In the present form of the instrument, this mean velocity is indicated directly on a meter calibrated in feet per second. Measurements can be made in aerated flows with air concentrations exceeding 70 or 80 per cent and at very high velocities. Velocity measurements with the new velocity meter in nonaerated flows check within 1 or 2 per cent of those made with a Pitot tube. The integrated water discharge inan aerated flow stream, taking into account both the measured air distribution and the velocity distribution and making reasonable estimates of the water discharge through the boundary areas have also checked the water discharge through the boundary areas have also checked the water discharge measured directly with an accuracy of 1.5 per cent.