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We performed numerical study on Uji River with an objective to analyze the channel hydromorphological characteristics including bank erosion process. Simulation results suggested that the overall channel evolution is insignificant but the bank erosion is dominant at several locations. It was also concluded that the bank erosion is mainly caused by the undercutting of the bank toe due to the low flow condition which induce high bed shear stress and high near bank velocity. With higher flow discharge, the zone of maximum velocity tend to shift more towards the channel center. Results of the prediction of bank erosion indicated that fluvial erosion due to the scour near the bank toe is dominant at most of the locations in Uji River.

The current study examines the evolution of alluvial meandering channels based on the laboratory experiments as well as field study. Experiments were conducted in erodible meandering channels to represent the natural scenario. Channel planform, as well as bed evolution, were analyzed. In the case of natural channels, time series satellite images were analyzed to understand the channel planform behaviour and bank erosion characteristics were analyzed through the real field data and photos. Results showed that the channel evolution characteristics vary from one alluvial meandering channel to another depending upon various channel parameters. It was found that low sinuosity channels and newly developed meander bends have higher tendency to migrate as well as undergo rapid channel adjustment. Bank protection counter-measures were effective in minimizing the bank erosion. At the same time, they tend to shift the point of erosion from one location to another.

Hydrodynamics Abstract

In climate regions with lower average daily solar radiation, such as the Pacific Northwest, a solar energy collector might not economically satisfy year-round domestic water heating demands, requiring an auxiliary unit, such as a natural gas water heater. Previous studies of such hybrid systems have shown that the efficiencies achieved while running in combined solar/gas mode was lower than expected. This inefficiency was attributed to a reduction in gas burner efficiency when the process fluid was partially pre-heated by the solar input. To predict the actual energy and cost savings under various design conditions, the performance of solar/gas hybrid systems must be better understood. In this work, the performance of a commercial hybrid solar/gas system is experimentally characterized to evaluate individual component and overall system efficiency. The hybrid water heating system consisted of three flat plate collectors arranged in series (total area = 6.44 m2), and a 22.3 kW natural gas burner. Under different temperature lifts and solar insolation values, the system was operated at three different modes of heating: solar, gas, and combined solar/gas mode. Efficiency value for each mode was calculated. Based on the experimental efficiency results, a configuration that would provide higher efficiency for combined solar/gas heating is suggested.