Characteristics Research of Nozzle in the Artificial Rainfall System
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Abstract:
The characteristics of nozzle in artificial rainfall system are modelled and simulated.According to the rain intensity distribution data of the nozzle under different pressures,the curve of the rainfall intensity and the radius is obtained.A plurality of nozzles are used to realize the rain intensity change continuously in the range,the overlap of the effective multi-nozzles radius is used to rain uniformly.A detailed design of the artificial rainfall simulation software is provided.Through the comparative analysis of two layouts,the square arrangement is selected,which can greatly improve the effective area.It provides important guiding significance on the selection and layout of the nozzle and research on artificial rainfall system.Keywords:
Intensity
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Convective storm detection
Weather radar
Hydrological modelling
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A computer-PLC (Programmable Logic Controller) control solution was proposed for the artificial trough rainfall simulator. The rainfall process with continuous changing intensities was simulated automatically with the control strategy. Frequency-tunable pulse signal of specified duty ratio was generated precisely using pulse module of PLC to drive nozzles oscillating at required frequency. Thus, arbitrary rainfall intensities within the output range of the simulator were achieved. Control configuration for trough rainfall simulator was built using Forcecontrol man-machine software. Parameters settings and rainfall intensities tracking during the rainfall simulation were realized. Simultaneously, a rainfall simulator performance evaluation procedure was performed based on a single nozzle rainfall test with six selected working states. A criterion of dynamic rainfall uniformity was proposed to estimate the performance of a rainfall simulator during the entire rainfall simulation. A Locally weighted scatterplot smoothing (LOESS) and weighted averaging approach was adopted in the evaluation procedure.
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Impacts of watershed morphologic and topographic structures, and spatial-temporal variations of rainfall on the unit hydrograph (UH) have been a key issue for investigation of watershed flow routing. In this paper we developed a new method to derive UH by considering the spatial-temporal variations of rainfall. The new method is based on the S-curve approach from a cumulative curve of UH. A nonlinear function with two parameters was used to fit the S-curve. These two parameters were found to be related to the barycentre of storm and the intensity of rainfall in the basin which describe the spatial-temporal variations of rainfall. The nonlinear relationship between two parameters of the S-curve function and the barycentre of storm and the intensity of rainfall is established by using an artificial neural network (ANN). Therefore, the unit hydrograph derived from the new method integrates with changing positions of storm barycentre and intensity of rainfall, and thus has characteristics of the Sherman unit hydrograph and a function of the description of the temporal-spatial variations of rainfall. This method is successfully applied in the Juhe catchment of the Yangtze basin, China. The simulation results show that this method is effective in watershed flow routing.
Watershed area
Flow routing
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Abstract. Distributed hydrological models require fine resolution rainfall inputs, enhancing the practical interest of space-time rainfall models, capable of generating through numerical simulation realistic space-time rainfall intensity fields. Among different mathematical approaches, those based on point processes and built upon a convenient analytical description of the raincell as the fundamental unit, have shown to be particularly suitable and well adapted when extreme rainfall events of convective nature are considered. Starting from previous formulations, some analytical refinements have been considered, allowing practical generation of space-time rainfall intensity fields for that type of rainstorm events. Special attention is placed on the analytical description of the spatial and temporal evolution of the rainfall intensities produced by the raincells. After deriving the necessary analytical results, the seven parameters of the model have been estimated by the method of moments, for each of the 30 selected rainfall events in the Jucar River Basin (ValenciaSpain) – period 1991 to 2000, using 5-min aggregated rainfall data series from an automatic raingauge network.
Intensity
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The simulation of the subsurface and surface flow is based on easch other under rainfall conditions; a coupling method is used to solve the problem accurately. The subsurface and surface flow coupling equation is formed and its computer program is compiled using the FEM. A method is presented to speed the convergence and to judge the saturation of the surface. The simulation results show that the speed convergence is feasible and very fit for the real phenomenon in the nature. It is helpful to analyze the reason for rainfall-induced landslides.
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In designing an effective and economic hydraulic structure for flood control, an optimal design of rain gauge network is important as it produces fast, accurate and important rainfall data. In this paper, geostatistical method integrated with hybrid of particle swarm optimization-simulated annealing is used to simulate the optimal locations and number of raingauges station. The simulation process used different generated rainfall data based on real rainfall data. The rainfall data randomly generated based on the exponential semivariogram model and it showed similar characteristics with the mean and standard deviation that is almost the same with real rainfall data. The proposed method successfully obtained the optimal number of rain gauges despite different sets of generated rainfall data. This situation shows that the proposed method is adequate to be applied in another case study, in other places or different data.
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Based on the principle of momentum theorem and water balance the basic equation for describing the runoff generated on a slope under the condition of natural rainfall with different rainfall intensities,rainfall momentum and influence of wind taken into account is deduced.The equation can be numerically solved by applying the Preissmann format.The feasibility of the model is verified by field experimental data.The maximum deviation between calculation result and experimental data is about 11%.
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ABSTRACT: Continuous rainfall patterns are currently simulated by approximating them by stair‐stepped (piece‐wise) patterns. The effects of this approximation on infiltration and runoff processes are not well known. A new technique for simulating smooth‐variable intensity rainfall patterns is presented. This technique is based on the fundamental principles of a moving water head in a container. The proposed technique is general and capable of simulating any rainfall pattern. However, as the rainfall pattern gets more complicated, the equipment required for simulation becomes more involved. The proposed technique has been tested experimentally. A close agreement was found between the theoretical and experimental simulations. It is concluded that the proposed technique might be very useful in studying the infiltration and runoff processes under variable intensity rainfall, especially for simple convex patterns.
Infiltration (HVAC)
Intensity
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