Calibration of rainfall simulator with different jets and pressure conditions

James Kobina Mensah Biney, BSc

Diplomová práce

Abstract:

ABSTRACT It is a fact that without rainfall simulators it would have taken a longer period obtaining data for assessing the impact of different types of rainfall on the environment. Rainfall simulators have been and continue to face a lot of issues since it was developed in the 1930s.One of this issue has to do with their inability to mimic the characteristics of natural rain. Due to the lack of standard design and measurements, most researchers end up developing devices suiting their particular needs, but the issues still persist. Rainfall features which include rainfall intensity and its spatial uniformity, drop size distribution, frequency, seasonal pattern, kinetic energy, and duration confirm that natural rainfall conditions are simulated with sufficient accuracy. This work seeks to calibrate an existence rainfall simulator in the laboratory to determined its usefulness for other field purposes in the future.The simulator used was a single nozzle type which was developed by the department of Water Resources and Environmental Modelling (Czech University of Life Sciences). Three different Lechler nozzles were each used for the calibration (fixed depth of 160cm) with pressures of 1.6, 1.8, 2.0, and 2.2 bars. Constant flow throughout the experiment was provided by an electrical pump. The rainfall spatial distribution was measured with 82 (three different categories of size) vessels serving as rain gauge equally distributed on the experimental plot (100 by 100 cm). An assessment for the coefficient of determination, spatial drop size distribution (creating of distribution maps), spatial variability (use of boxplot) and the calculation of Christiansen coefficient of uniformity (CU) were all based on the collected data. Though the CU values range from 65% to 88%, the expectation was to achieve a CU value of 80% and more, but it was only the nozzles with the highest discharge that show that range of 80% and above signifying a uniform spatial rainfall distribution. The result also shows that the generated rainfall characteristics of spatial variability and that of the spatial rainfall distribution in rainfall simulator, just like in natural rainfall event, are not homogeneous. So, for continuous simulation of natural rainfall, it will be very difficult to achieve the same characteristics. The rainfall intensity generated for this work range from 16.03mm/h to 55.19mm/h.

Keywords

Calinration of rainfall characteristics, Nozzle-type rainfall simulator, Rainfall intensity, Drop size distribution, Spatial variability

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 18. 4. 2017

Obhajoba závěrečné práce

• Vedoucí: Ing. Jiří Pavlásek, Ph.D.

Česká zemědělská univerzita v Praze

Fakulta životního prostředí

Magisterský studijní program / obor:
Krajinné inženýrství / Environmental Modelling