Tatsuaki Nakato

Numerical simulations of inviscid three-dimensional flows at single- and dual-pump intakes

Three-dimensional inviscid solutions for pump-approach flow distributions within both a single-pump and a dual-pump sump model were developed. The single-pump sump model consisted of a rectangular pump bay with a vertical circular pipe located at the downstream end of the bay. The two-pump sump model consisted of a wider rectangular pump bay with two vertical circular pipes located at the downstream end of the bay. The equations of motions were solved in generalized curvilinear coordinates on a non-staggered grid. For the single-pump model, the simulations were carried out for two cases, cross-flow and no-cross-flow. The results are in good agreement with laboratory flow measurements obtained from a 1:10-scale model using an Acoustic Doppler Velocimeter. For the two-pump sump model, simulations were also carried out for two cases. In Case 1, an equal pumping discharge was delivered through the two pipes, and in Case 2 the total discharge was split in a 7-to-3 ratio between the two pipes. The results for the two cases were compared with a focus on the formation of free-surface and subsurface vortices surrounding the pumps.

A review of scour conditions and scour-estimation difficulties for bridge abutments

This paper is a review of the scour conditions, and scour-estimation difficulties, associated with scour at abutments of bridges over rivers and streams. A recent survey of abutment-scour problems in the U.S., Korea, and abroad, shows that several scour conditions can occur, and that existing relationships for scour estimation, besides being inaccurate do not match the scour conditions. Moreover abutment scour is found to be primarily a concern for bridges over smaller rivers and streams than for larger rivers, because inadequate design and monitoring attention has been give to abutment scour at the many small bridges. This paper also discusses the difficulties confronting accurate estimation of abutment-scour depth. The difficulties, which include similitude aspects of laboratory experiments on scour at bridge abutments, complicate the development of reliable scour-estimation relationships. In a practical sense, the difficulties imply that design relationshipsfor scour-depth estimation inevitably have to be of approximate accuracy given the great variability of channel conditions at most abutments.

IOWA SEDIMENT CONCENTRATION MEASURING SYSTEM

A significant portion of the damage by hurricanes is the storm surges. The National Weather Service has developed a dynamical-numerical model to forecast hurricane storm surges. The model is used operationally for prediction, warning, and planning purposes. The model requires fixed oceanographic and real time meteorological input data. The oceanographic data were prepared for the Gulf and East coasts of the U.S. and are stored as an essential part of the program. Meteorological data for any tropical storm are supplied by the forecasters or planners using the model. The model was applied to hurricane Camille 1969. Comparison between the observed and computed surges for Camille was satisfactory for prediction purposes.The main consideration in harbor master planning is to maximize the amount of time that the harbor can be used. The potential level of harbor utilization can be evaluated by analyzing vessel performance during harbor operations in terms of the range of imposed environmental conditions. The harbor utilization level is expressed statistically as the probable amount of time that the harbor can be used as planned.The design and construction of a major ocean outfall and diffuser system for disposal of wastewater effluents is a complex process involving an interplay of requirements originating from various disciplines. These include, among others, considerations of physical oceanography, mixing and dispersion, treatment processes, regulatory requirements, marine geology, economics and construction. The recently completed Sand Island Outfall and the newly designed Barbers Point Outfall are both on the southern coast of the island of Oahu, Hawaii, and are designed for treated sewage effluents from the densely populated portion of the City and County of Honolulu. In this paper, some design considerations of these outfalls will be examined. The emphasis in this paper is on the hydrodynamics, although other design aspects are also discussed briefly.The height of dikes and other coastal structures can only be calculated after determination of the wave run-up. Several formulas for the calculation of wave run-up are developed after model tests as a rule. But the influences of scale effects and natural wind conditions are practically unknown. To clear these questions further investigations and especially field measurements should be carried out. By measuring the markerline of floating trash on the slope of the seadikes the maximum wave run-up could be found out after four storm surges in 1967 and 1973In two graphs it will be shown that on the tidal flats the run-up depends on the waterdepth. The run-up was higher than it could be expected after model tests of 1954. With a newly developed special echo sounder the run-up could be measured in January 1976. The waves and the run-up could be registrated synchronously during two severe storm surges. As shown in Fig. 9 it was found a logarithmic distribution of the wave height, wave period and the higher part of the wave run-up. The found wave run-up is considerably higher than estimated before. The measured 98 % run-up is found about twice the computed value. That is an interesting and important result of the first synchronous recording of wave run-up on sea dikes.In March 1972 the authors firm in association with two Portuguese firms of consulting engineers, Consulmar and Lusotecna, were appointed by the Portuguese Government agency Gabinete da Area de Sines to prepare designs for the construction of a new harbour at Sines on the west coast of Portugal. The location is shown in Figure 1. The main breakwater, which is the subject of this paper, is probably the largest breakwater yet built, being 2 km long and in depths of water of up to 50 m. It is exposed to the North Atlantic and has been designed for a significant wave height of 11 m. Dolos units invented by Merrifield (ref. 1) form the main armour. The project programme required that studies be first made of a wide range of alternative layouts for the harbour. After the client had decided on the layout to be adopted, documents were to be prepared to enable tenders for construction to be invited in January 1973. This allowed little time for the design to be developed and only one series of flume tests, using regular waves, was completed during this period. Further tests in the regular flume were completed during the tender period and a thorough programme of testing with irregular waves was commenced later in the year, continuing until August 1974 when the root of the breakwater was complete and the construction of the main cross-section was about to start. The model tests, which were carried out at the Laboratorio Nacional de Engenharia Civil in Lisbon, were reported by Morals in a paper presented to the 14th International Coastal Engineering Conference in 1974. (ref. 2)Estuaries may be sequentially classified into highly stratified, moderately mixed and vertically homogeneous. An important difference between moderately stratified or vertically homogeneous estuaries, and highly stratified estuaries (salt wedges) is that, in the former, tidal currents are sufficient to cause turbulent mixing of fresh water and sea water over the full depth of the estuary. In the latter, a distinct interface or interfacial layer exists which separates the two nearly homogeneous layers. The vertical advectlon of salt in this two-layer flow is the dominant process in maintaining the salt balance. This paper presents an analytical model describing this process. Experiments have been conducted in the laboratory to compare with the developed theory.

John Fisher Kennedy - student and statesman of hydraulic engineering

ABSTRACT John Fisher Kennedy (1933–1991) had a remarkably accomplished career in hydraulic engineering, including his service as President of the International Association for Hydraulic Research (1980–1983). Though alluvial river behaviour was the hydraulics topic closest to his heart, Kennedy also made scholarly contributions to other hydraulics topics: notably, river thermal and ice processes, the design and operation of thermal- and hydro-power plants, as well as various hydraulic structures. He had an energetic entrepreneurial spirit and was an engaging communicator, often speaking and writing about progress in hydraulic engineering, history of hydraulics, and leadership in hydraulics. Additionally, as a bibliophile he was always keen to share his knowledge of culture, history, and music. His impressive career as marked by many achievements including being one of the youngest engineers ever elected to the prestigious US National Academy of Engineering. We reflect upon Kennedys work and the qualities that made him a prominent engineer and educator.

Application of Suction Scoops to Improve Pump-Approach Flow Distributions in Three-Pump Intake Bays

Two geometrically undistorted models of St. Louis Water Companys Meramec Plant Intakes 1 and 2 were constructed at a scale of 1:5 in order to solve chronic pump vibration problems. Because of the unconventional layouts of small, deep, rectangular pump pits with three pumps each, vertical -pump inverted drafttubes (VPIDs) were developed. Each intake chamber was divided into three individual bays using two vertical partition walls. Each VP ID included a two-segment straightline suction scoop, a floor splitter, a backwall splitter, two sidewall floor -corner fillets, two vertical backwall corner fillets, flow -turning vanes, and a vertical guidewall at the VPID entrance. In this paper only modeling efforts on Intake 1 are described. This is the second VPID model designed by IIHR – Hydroscience & Engineering (IIHR), The University of Iowa.