Water is fundamental to human life, and the ways in which a society uses it can tell us a great deal about a people. The ancient Greeks and Romans had at their disposal several mechanical ...water-lifting devices. The water-screw, the force pump, the compartmented wheel, and the bucket-chain were developed by scientists associated with the great school at Alexandria. Application of these devices was sporadic in the Hellenistic world, but they, and the later saqiya gear, were used in a wide range of rural and urban settings in many parts of the Roman Empire. Professor Oleson has prepared a definitive study of mechanical water-lifting devices in the Greek and Roman world. He systematically and thoroughly examines the literary, papyrological, and archaeological evidence for the devices and considers the design, materials, settings, costs, effectiveness, and durability of the many adaptations of the small basic repertoire of models. The literary and papyrological materials range from Deuteronomy to papyri of the seventh century AD, and the archaeological sites discussed range from Babylon to Wales. An extensive collection of illustrations complements the literary, papyrological, and archaeological evidence for this remarkable ancient technology.
Pump as Turbine (PAT) is an effective alternative of power generation for small hydropower system. Since the characteristic curves under turbine mode are not supplied by manufacturer of pumps, the ...theoretical model for energy performance of centrifugal turbomachinery under pump and turbine modes is proposed by means of detailed modeling of losses inside hydraulic machinery. Based on the theoretical model, a flowrate-based iteration method is proposed to determine the best efficiency point (BEP) under turbine mode. In order to validate the accuracy of established theoretical model, case studies are carried out under three centrifugal pumps, with the specific speed varied from 103 to 187, and the predicted results by theoretical model are compared with experimental measurements and numerical simulations. It is found that the average relative variations for prediction of pump head and efficiency are 6.12% and 5.51%, respectively, and they are 5.40% and 3.63% for turbine head and efficiency, which is of sufficient accuracy for engineering practice. The predicted BEP under turbine mode is also of great accuracy, with relative variation of 1.28% on average. In addition, the PAT performance as well as losses under pump and turbine modes have been analyzed in detail.
•Theoretical model of energy performance prediction for pump as turbine is proposed.•Flowrate-based iteration method of best efficiency point (BEP) determination is proposed.•Three pumps with specific speed of 103, 131 and 187 are investigated.•Losses of centrifugal pump and PAT under various flow rates are analyzed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
On behalf of IAHR Asia Working Group (AWG), we are pleased to conclude the 3rd IAHR-Asia Symposium on Hydraulic Machinery and Systems (IAHR-Asia 2021), which was held on November 22-23 in Kathmandu ...University, Nepal.Seventy full papers were presented in two days of the conference whereas four invited and four featured presentations were also given by eminent personalities of the field. Presentations were broadcasted both in a physical mode and virtual mode in four groups of sessions, each group consisting four parallel sub-sessions. It was our privilege to welcome the keynote speakers of the symposium: Prof. Avellan from Swiss Federal Institute of Technology, Lausanne, Prof. Young-Ho Lee from Korea Maritime and Ocean University, Prof. Zhengwei Wang from Tsinghua University, and Prof. Chisachi Kato from The University of Tokyo. We would also like to thank all the organizers, presenters and participants who were involved in this symposium.The list of Conference Organizing Committee, Local Organizing Committee, International Advisory Committee, International Technical Committee are available in this pdf.
Abstract A level-set based sharp-interface immersed boundary method (IBM) was applied with large eddy simulation to simulate the complex flow field around a marine propeller. The wake characteristics ...under the open-water conditions including velocity, pressure and turbulent kinetic energy were analyzed. Additionally, the comparative analysis of the axial Reynolds stress of the propeller operating beneath incident waves and that under the open-water condition indicates that the nonlinear interaction between waves and wake leads to the increase in Reynolds stress within the radial range of r / D =0.35 to r / D =0.55 in the far-wake region. The obtained numerical simulation results confirmed the feasibility of the IBM for the numerical simulation of complex flows through hydraulic machinery such as propellers.
Abstract In order to control cloud cavitation, the bio-inspired leading-edge tubercles are implemented on a NACA0015 hydrofoil. The cavitation experiments in a water tunnel are conducted to elaborate ...on the dynamic behaviors and control mechanisms. As observed, the cavitation with a mean length of 0.38 times chord length on baseline hydrofoil performs three-dimensional features and multiple shedding by the re-entrant jet impingements. Under the equivalent cavitation condition on LET hydrofoil, the cavities with a frothy appearance are produced and confined within the troughs, and the large-scale shedding and re-entrant jet are not identified. The proper orthogonal decomposition (POD) based on cavitation images is carried out to extract the dominant shedding structures. The leading modes of POD on baseline hydrofoil dictate the main shedding of cloud cavitation. The lateral cavities on the LET hydrofoil are well separated by the spanwise periodic tubercles and then the dominant POD modes appear as small-scale vortex pairs. The leading-edge tubercles could depress the three-dimensional cloud cavitation and the re-entrant jets, which is a promising method to control cavitation unsteadiness in hydraulic machinery.
Abstract The sediments in the flow cause deterioration of components of the hydraulic machinery and influence fundamental properties such as density and viscosity of the flowing fluid. Earlier ...researchers have demonstrated the influence of sediment-laden flow on the performance of pumps, but such investigations have not been performed for the Francis turbine. This research focused on the effects of sediment-laden flow on the performance of a Francis turbine. Hydropower Research Centre for Himalayan Region (HRCHR) had a laboratory facility especially designed to conduct tests on Francis Turbines with sediments in the flow. The test rig was a closed-loop type and had provisions for mixing sediments with water and maintaining a uniform sediment concentration throughout the circuit. The performance of a 2 kW Francis turbine was tested at three different GV (Guide Vane) angles for different load conditions with and without sediment in the flow. The results showed that there was no change in maximum efficiency in the case of a smaller GV opening, whereas the maximum efficiency in the case of sediment water was reduced for a larger GV opening. Meanwhile, Sediment particles did not affect the head under the same discharge, whereas output power decreased slightly for sediment-laden conditions.
•Acidic and alkaline solution exhibited inhibitory effect against cavitation.•Acidic solutions have higher inhibitory effect than alkaline solutions.•The cavitation degree and flow length increased ...with higher deviation from pH = 7.•The cycle period reduced with higher offset value from pH = 7.•Acidic solutions should be used as reference for magneto-hydraulic sealing design.
Owing to the different pH values of water resources in different places, it is not practical to design hydraulic–mechanical magneto-hydraulic sealing devices under clean water conditions. This study used a Venturi structure to analyze the relationship between the solution pH and cavitation. A high-speed camera and turbine flowmeter were used to record the primary cavitation flow rate, shedding period of the cavitation cloud, and flow direction length of the cavitation cloud of solutions with different pH values. The results showed that acidic and alkaline solutions can inhibit the occurrence of primary cavitation. Compared with clean water, acidic and alkaline solutions have longer cavitation cloud flow length, shortened cavitation cycle, and higher degree of cavitation. In detail, the degree of cavitation in the acidic solution is stronger than that in the alkaline solution. Therefore, the amplitude of the pressure pulsation in an acidic solution should be taken as the reference when designing a hydro-mechanical magneto-hydraulic sealing device.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
