Browsing by Author "Arndt, Roger E. A."
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Item Assessment of design considerations and Field Repair procedures to mitigate cavitation pitting in Hydraulic turbines(1984-12) Voigt, Rick; Arndt, Roger E. A.Cavitation erosion in hydraulic turbines is of major importance to all members of the hydroelectric community. This erosion is caused by the collapse of vapor bubbles against or very near turbine surfaces. These bubbles are formed in regions where the absolute pressure falls below the vapor pressures of the fluid. Nuclei flowing through these regions experience tension and quickly develop into vapor bubbles. These bubbles then rapidly collapse, creating very high pressure waves emanating from the center of collapse. When the bubble collapse occurs near a material surface, a minute crater may be formed. Over a period of time this can lead to the spalling of material, which will eventually require remedial measures in order to insure continual successful turbine operationItem Cooperative Investigation of Jet Flows(St. Anthony Falls Laboratory, 1984-03) Arndt, Roger E. A.; Long, Dean F.The objectives of the Minnesota study were to determine the nature of acoustic radiation from turbulent jets, with both Reynolds and Mach number similitude. Acoustic data were to include intensity, directivity, spectra and narrowband spatial coherence. Emphasis in the initial study was to be on naturally developing jets. A second phase of the program was to be aimed at artificially excited jets. In order to carry out the experimental program as originally envisioned, a special test facility had to be constructed. This test rig had to produce jets of varying diameter, with minimal turbulence levels at the nozzle erlt and be essentially free of acoustic contamination. As it turns out, the latter requirement was essential to the successful completion of the project. The desire to model high subsonic Mach number at low Reynolds number necessitated high speed jets of very small diameter. The high frequency content in these jets necessitated that special emphasis be placed on bothItem Experimental Development of a Novel Aeration Device(St. Anthony Falls Hydraulic Laboratory, 1994-04) Ramanathan, V.; Arndt, Roger E. A.Theoretical and experimental studies were carried out with the aim of developing an improved aeration device. Many of the aeration devices currently in use contain fine pores, through which air is pumped to produce small bubbles in the diameter range of 2 to 3 mm in water, the objective being optimum performance in terms of mass transfer. Because of the very small pore size, these devices are often subject to clogging, consequent deterioration of efficiency and escalation of power requirements. The development of the new aeration device, named the SAF diffuser, is an attempt to generate bubbles of the optimum size range using relatively larger orifices so that the diffuser clogging and the energy requirements can be reduced. The SAF Diffuser comprises a vertical draft tube immersed in the water body to be aerated. A buoyancy: induced flow is created within the tube by injecting air through 0.5 mm diameter peripheral orifices located near the inlet end. The induced flow exerts a drag force on the bubbles that are being formed at the peripheral orifices. This drag force causes the bubble to detach, from the orifice before it grows to the normal size attained in stagnant water. Utilizing this concept, hole sbes that are larger than (about 15 times) those used in conventional fine pore diffusers are possible. For a given air flowrate, the induced velocity and hence the bubble size depends upon the tube dimensions. This dependence provides a novel technique to control the bubble size. Theoretical and experimental study of the air-water flow as well as the mass transfer characteristics of the device were undertaken. Simple methods of measuring the two phase flow parameters were developed. Through theoretical analysis and experimentation, non-dimensional correlations to predict the phase velocities within the device as well as the mass transfer characteristics of the device were developed. The studies showed that for medium depth applications, the device can operate with 10 to 20 percent higher aeration efficiencies than conventional designs. Even higher efficiencies are possible in the low depth applications typical in aquaculture.Item An Experimental Investigation of the Influence of Air Bubbles on the Acoustic Radiation Efficiency of Turbulent Shear Flow(St. Anthony Falls Hydraulic Laboratory, 1987-04) Arndt, Roger E. A.The objective of this program is to experimentally examine the interaction of a turbulent mean flow with entrained air bubbles. Particular attention has been paid to the determination of the relative acoustic radiation efficiencies of bubbles undergoing simple harmonic oscillation and those undergoing splitting.Item Extended Phase A-2, Large Cavitation Channel, Davld Taylor Naval Ship Research and Development Center(St. Anthony Falls Laboratory, 1984-08) Arndt, Roger E. A.; Song, Charles C. S.; Silberman, Edward; Killen, John M.; Wetzel, Joseph M.; Yuan, MingshunIt was suggested that a mild contraction located immediately upstream of the pump may improve the quality of flow which is expected to be quite nonuniform coming from the diffuser and the first and second elbow. To investigate the effect of the contraction ratio, the AROl computer model previously used in the Phase A-2 studies for the Large Cavitation Channel (LCC) main contraction design was applied to the pump contraction. As shown in Fig. 1, the contraction is assumed to be 5.563 m long and of circular cross section. Area contraction ratios of 0, 10, 20 and 30 percent were used. There is a fixed shaft of constant diameter along the centerline of the contraction. Two different shaft diameters, 0.508 m and · 1.016 m, were used based on information available at the time the study was conducted~ Initially, a fifth order polynomial was used for the contraction profile. The profile was later changed to a straight line because the contraction is so mild that the flow is not significantly affected by the boundary shape. Due to symmetry about the vertical plane, only half of the flow region was modeled. Different types of nonuniform inflow velocity profiles were studied. A total of 46 modeling runs covering various geometrical and flow conditions as well as different modeling parameters were made.Item Feasibility Study of a Hydrodynamic Test Facility at the Detroit Dam(St. Anthony Falls Laboratory, 2002-06-30) Wetzel, Joseph M.; Arndt, Roger E. A.In considering the technology necessary to develop ships in the 70 to 100 knot range, it becomes evident that some form of drag reduction will be necessary to achieve this goal. Several viable drag reduction techniques have been studied for many years. These include surface striations, polymer injection and micro-bubble injection. The latter technique shows great promise with drag reduction of about 80% having been demonstrated. In order to adapt a drag reduction concept in the fleet, it is essential that studies be made that simulate, as closely as possible, prototype conditions. This leads to the need for a test facility that can achieve flow velocities in the 70-knot range. At present there are no hydrodynamic test facilities that fall in this category. However there is an existing Corps of Engineers test facility that could be adapted and modified to suit the Navy’s test requirements. This facility is located at the Detroit Dam and Lake on the North Santiam River near Detroit, Oregon. This is a multipurpose facility designed for flood control, navigation, irrigation and power. A powerhouse is situated at the base of the dam that has two 50 MW units installed. In addition to the two penstocks for power production, there is an additional, gated bottom outlet that supplies water to an eight-foot diameter penstock. A rudimentary flume is fitted to the outlet this penstock that discharges directly into the tailwater of the plant. At high water elevation, approximately 320 feet of head is available at the test site. In the absence of losses this equates to a maximum velocity of 83 knots. Maximum head is available for about 4 to 5 months out of the year. The conduit has not been used for over 20 years, and very little information regarding its performance is available. The conduit consists of an 8 ft diameter steel pipe with its intake located about 225 ft below the summer water level and its exit 320 ft below the summer water level. The winter reservoir level is about 115 ft lower. A small rectangular test section has been attached to the exit of the 8 ft diameter pipe about 25 years ago. It was used for a particular purpose and abandoned after the work was completed. It is assumed that this section has no further use, and is subject to removal. It is the purpose of the present investigation to determine the hydrodynamic capabilities of such a facility. Preliminary results of the study are summarized in the following sections.Item Final Techincal Report: Research Program in Hydroacoustics(St. Anthony Falls Hydraulic Laboratory, 1987) Arndt, Roger E. A.; Higuchi, Hiroshi; Kaveh, Mostafa; Lambert, Robert; Plunkett, Robert; Ikohagi, Toshiaki; Arakeri, VijayThis program is concerned with two major problems in hydroacoustics; namely the nature of the low wavenumber characteristics of turbulent boundary layer pressure fluctuations including their relationship with structural vibration, and cavitation noise from tip vortices.Item Hydrodynamic Analysis of the Hykat(St. Anthony Falls Hydraulic Laboratory, 1987-06) Song, Charles C. S.; Wetzel, Joseph M.; Yuan, M.; Arndt, Roger E. A.; Killen, John M.The St. Anthony Falls Hydraulic Laboratory has carried out a hydrodynamic analysis of several critical components of a preliminary design configuration of the HYKAT. A sketch of this configuration is shown in Fig. 1. The components subjected to detailed analysis were those of the upper leg, including the contraction, turning vanes of the first elbow, and the turbulent management system. Head loss computations were made for the entire flow circuit. Mathematical modeling was used extensively for analysis of the contraction and the turning vanes. Based on the results of this study, recommendations have been made for some modification to the preliminary design. Some of the results presented here have been previously included in progress reports, and results of additional studies are summarized.Item Independent Turbine Testing and Research(St. Anthony Falls Laboratory, 1987-08) Voigt, Richard L. Jr.; Gulliver, John S.; Wetzel, Joseph M.; Arndt, Roger E. A.The St. Anthony Falls Hydraulic Laboratory (SAFHL) is presently upgrading their Turbine Test Facility. Completion of the upgrade, including checkout tests, is scheduled for Fall 1987. This paper will discuss the improvements being made to the Facility. The upgrades include enclosure of the upper portion of the test loop (head tank, tail tank, and dynamometer), to enable year-around operation. A temperature control system is being constructed and installed in the test loop which will provide temperature stability, necessary for cavitation testing, and required by IEC model test codes. Installation of additional instrumentation will provide for simpler, more efficient, data acquisition. The Facility is being connected to the Laboratory compressed air and vacuum facilities for pressure control. The existing Laboratory deaeration equipment will be incorporated to allow accurate dissolved gas content control not generally available in turbine test facilities. The SAFHL Turbine Test Facility will be available to undertake specific projects for the hydropower community funded by a variety of industries, agencies, and organizations. Projects might include performing model tests for small manufactures, prototype tests of micro-turbine units, model acceptance tests, comparative model tests, as well as a wide range of basic research experiments. The Facility will also be used as a demonstration tool in the instruction of students and hydropower engineers as part of SAFHL's active hydropower education program.Item Investigation of the Use of Air Injection to Mitigate Cavitation Erosion(St. Anthony Falls Laboratory, 1993-09) Arndt, Roger E. A.; Paul, Saurav; Ellis, Christopher R.This project was initiated as part of a new research and development focus to improve hydropower generation. One aspect of the problem is severe cavitation erosion which is experienced when hydroturbines are operated at best power and in spinning reserve. Air injection has been used successfully to minimize or eliminate cavitation erosion in other applications. Thus, an investigation was initiated to determine whether or not air injection would be an effective solution for turbine erosion problems. A specially instrumented hydrofoil of elliptic planform ·and a NACA 0015 cross section was tested at flow velocities up to 20 m s·I, at various values of cavitation index. Pitting rate was not measured directly but was inferred from direct measurement of impulsive pressures on the surface of the hydrofoil and by monitoring accelerometers mounted at the base of the hydrofoil. Cavitation noise was also measured by a hydrophone positioned in the water tunnel test section. Air was injected through small holes in the leading edge of the foil. Air injection was found to be very effective in minimizing erosion as inferred from all three cavitation erosion detection techniques.Item Noise Generation of Air Bubbles in Water: An Experimental Study of Creation and Splitting(St. Anthony Falls Hydraulic Laboratory, 1987-12) Frizell, Kenneth Warren; Arndt, Roger E. A.Although the study of two-phase flow, especially air-water mixtures, has received much attention in recent years, little has been done concerning the noise' generated by non-cavitating air water flows. The main purpose of this work is to examine these flows; in particular, to look at the noise associated with the creation of air bubbles at a nozzle, and the noise radiated by air bubbles splitting in the shear layer of a submerged turbulent water jet. Experiments were conducted to measure the sound pressure levels associated with bubble creation and bubble splitting, under a variety of conditions. Comparison were made with existing theories. An improved physical understanding of the mechanism of noise generation was gained through data analysis and photographic studies. Recommendations for further research are given.Item Phase A-2, Large Cavitation Channel, David Taylor Naval Ship Reasearch And Development Center(St. Anthony Falls Laboratory, 1983-08) Wetzel, Joseph M.; Bintz, David W.; Arndt, Roger E. A.; Morel, T.; Sharadchandra, Gavali; Song, Charles C. S.; Killen, John M.The Large Cavitation Channel (LCC) has very tight performance specifications for the flow quality in the test section, both for uniformity of the mean velocity profiles and turbulence levels. The mean velocity profiles have been addressed experimentally in the Task A report, and mathematically in the Task B report. This task is concerned with the turbulence levels in the test section. Turbulence levels are partially controlled bY,honeycomb design. Model studies of honeycombs should be conducted at as high a Reynolds number as possible to reduce scale effects. Thus, the decision was made not to utilize the undistorted 1 to 10 scale model of the preliminary Kempf and Remmers (K&R) contraction, test section, and diffuser that was used in the Task A studies as the Reynolds number based on honeycomb parameters was judged to be too low to obtain meaningful results. The existing wind tunnnel facility was modified for the turbulence measurements in rather an unique manner so that full scale honeycombs could be evaluated. These modifications were made after the tests of the Task A program were completed. Results of the turbulence measurements and recommendations for a turbulence management system for the LCC are discussed in the following sections.Item Preliminary Analysis Of Hydropower Production Feasibility At Twenty-One Existing Dam Sites In The State Of Minnesota(Saint Anthony Falls Laboratory, 1980-08) Gulliver, John S.; Garver, Rodrick J.; Arndt, Roger E. A.; Bowers, C. EdwardA preliminary estimate of hydropower production feasibility was made for twenty-one existing dam sites in the State of Minnesota. The purpose of the preliminary analysis was to determine whether a comprehensive feasibility study is justified for the site. The expected annual energy production and initial project cost were estimated for each site. Initial cost estimates include turbine, generator, transmission line, and other electromechanical features as well as the civil features of hydropower retrofitting. Initial cost does not include dam rehabilitation, since the required information is not available for 19 of the 21 sites. The "relative cost" of the project was defined as the initial cost divided by the annual energy production, and was calculated for each site. The relative cost and general curves for payback period were used to estimate hydropower feasibility at each site. The results of the preliminary analysis are: 5 sites have good or very good hydropower feasibility, 6 sites are marginal, and 10 sites have poor hydropower feasibility. Estimates of the cost of a comprehensive feasibility study are included for each site.Item The Role Of "Nuclei" In Tip Vortex Cavitation Inception(St. Anthony Falls Hydraulic Laboratory, 1986-08) Arndt, Roger E. A.; Arakeri, Vijay H.An analysis of the recently obtained 01 values for tip vortex cavitation inception from an elliptical planform hydrofoil is presented. This includes the estimation of critical a values for nuclei supply from the facility and separated regions on the foil. When measured 0i values are compared to these critical a values, certain obvious trends are noted. These have been used to estimate the dominant nuclei size at inception and are found to be surprisingly small. Thus, it is found that their role should be carefully examined in analyzing present inception data.Item The St. Anthony Falls Independent Turbine Test Facility(St. Anthony Falls Hydraulic Laboratory, 1989-07) Olivier, Cecilio; Voigt, Richard L., Jr.; Ramanathan, V.; Gulliver, John S.; Arndt, Roger E. A.In the summer of 1986, the Saint Anthony Falls Hydraulic Laboratory (SAFHL) was selected by the U.S. Department of Energy (DOE) for the development of an independent turbine test facility (ITTF). As a cost sharing project by SAFHL and the DOE, the establishment of an ITTF in the United States provides capabilities needed to the United States hydropower industry. The SAFHL ITTF will aid in the development of improved turbine designs, as well as provide a facility for cavitation, aspiration, and draft tube studies. In addition, the ITTF can provide access to model testing for small manufacturers, as well as being available for comparative model testing [1]. Finally, the ITTF is also a significant instructional tool in training of capable young hydropower engineers.Item U.S.-Romanian Workshop On Water Resources Engineering Volume I(St. Anthony Falls Laboratory, 1987-05) Kennedy, John F.; Odgaard, Jacob A.; Parker, Gary; Liggett, James; Katopodes, Nikolaos D.; Martin, Sam; Acosta, Allan; Arndt, Roger E. A.; Falvey, HenryThis report summarizes the formal presentations made at the U.S. Romanian Workshop on Water Resources Engineering held in Bucharest, Romania from July 21 to July 27, 1986. There are two volumes. Volume I is a summary of presentations made by the American delegation. Volume II is a collection of reprints authored by the American delegates. For brevity, only one copy of Volume II is complete, and that has been sent to Romania. All other copies of Volume ll contain a listing of the reprints submitted.Item U.S.-Romanian Workshop On Water Resources Engineering Volume II(St. Anthony Falls Laboratory, 1987-05) Kennedy, John F.; Odgaard, Jacob A.; Parker, Gary; Liggett, James; Katopodes, Nikolaos D.; Martin, Sam; Acosta, Allan; Falvey, Henry; Arndt, Roger E. A.This report summarizes the formal presentations made at the U.S. Romanian Workshop on Water Resources Engineering held in Bucharest, Romania from July 21 to July 27, 1986. There are two volumes. Volume I is a summary of presentations made by the American delegation. Volume II is a collection of reprints authored by the American delegates. For brevity, only one copy of Volume II is complete, and that has been sent to Romania. All other copies of Volume ll contain a listing of the reprints submitted.