The wind-induced undercatch of precipitation gauges is defined as the reduced amount of precipitation captured by the collector of the gauge with respect to the amount that would be captured if the gauge were transparent to the wind. When the gauge is exposed to the wind, airflow deformations occur above and upwind of the collector due to the bluff-body aerodynamics of the gauge outer geometry. Significant acceleration and vertical velocity components are generated (see e.g., Jevons, 1861;Warnik, 1953), inducing some deformation of the fall trajectories of the approaching hydrometeors and generally resulting in a lower collection of precipitation than in the absence of wind.Instrumental measurement biases for precipitation gauges, well described and addressed in the literature (see e.g., La Barbera et al., 2002;Molini et al., 2005;Valík et al., 2021), propagate through the applications or the modeling chain (Habib et al., 2008) and their awareness is often rapidly lost, yielding limited reliability of the obtained results (Lanza & Stagi, 2008). Similar implications to real-world hydrological applications are expected for the wind-induced undercatch.Adjustments for the wind-induced bias are traditionally derived from field experiments, where the ratio between the precipitation amount measured by the gauge and a suitable reference configuration with limited exposure to the wind is used as a measure of the Collection Efficiency (CE). This is a function of the wind speed at the collector's height and of further influencing variables, such as the microphysical characteristics of the precipitation events at the field test site. The choice of the influencing variables adopted to derive best-fit adjustment curves from the field-measured data affects the representativeness of the results and their transferability to any different site climatology and gauge configuration. This also reflects into
This works focuses on a series of experimental tests carried out to investigate overpressures in tunnels due to train crossings. Although the above-mentioned topic is well known and also defined in European standards, in the literature full-scale data are lacking, which are useful to validate the numerical codes required in the certification process and are used in train structural dimensioning. In this respect, an extensive full-scale experimental campaign was planned for observing as many test conditions as possible, such as single passages of different trains, two train crossing, different tests speed, and different tunnel characteristics. In detail, the understanding of the pressure wave generation and transmission is deeply enhanced by studying the pressure evolution both on board and at trackside, considering both single train passages or two trains crossings and having the possibility to compare aerodynamic loads on sealed and unsealed trains. Furthermore, the position of sensors, the speed of the train, and the initial conditions within the tunnel have been proven to be fundamental parameters for properly estimating the pressure loads on trains.
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