Gert Luyckx

Simplified method to correct rainfall measurements from tipping-bucket rain gauges

Tipping bucket rain gauges are commonly used in rainfall measurement campaigns. The main disadvantage of these devices is that they underestimate rainfall volumes at the higher rainfall intensities, due to the loss of water during the tipping action of the device. In this paper a new method is proposed to correct recorded rainfall data, without the need for a detailed calibration test. The comparison of the calibration results of 24 gauges (6 different types) shows an interesting relationship between the rain gauge resolution (rainfall depth corresponding to 1 tip) and the slope of its calibration curve. This relationship proves that the tipping time of the tipping mechanism has nearly the same value for every tested device. Therefore the slope of the regression line can be calculated theoretically and, as a consequence, one simple calibration test is enough to determine the complete calibration curve of any tipping bucket rain gauge. This test has to be carried out anyway in order to find the exact resolution of the device. Two monitored storm events, one moderate storm and one heavy storm, are used to study the possible influence of the correction method on calculated cumulative rainfall volumes.

Removal efficiency of swirl/vortex separators

In this paper an efficiency formula for swirl/vortex separators is proposed. It is based on the combination of scale model tests on a simple vortex separator and literature results from tests on similar devices. The formula predicts the removal efficiency of cylindrical overflow constructions as a function of flow conditions, chamber geometry and particle settling velocity. The formula has furthermore been used to make a comparison with the efficiency of a high-side weir overflow and a storage sedimentation tank.