João R.C.B. Abrantes

Mapping Soil Surface Macropores Using Infrared Thermography: An Exploratory Laboratory Study

Macropores and water flow in soils and substrates are complex and are related to topics like preferential flow, nonequilibrium flow, and dual-continuum. Hence, the quantification of the number of macropores and the determination of their geometry are expected to provide a better understanding on the effects of pores on the soils physical and hydraulic properties. This exploratory study aimed at evaluating the potential of using infrared thermography for mapping macroporosity at the soil surface and estimating the number and size of such macropores. The presented technique was applied to a small scale study (laboratory soil flume).

Prediction of skin surface soil permeability by infrared thermography: a soil flume experiment

This study presents a new technique to map soil surface permeability using infrared thermography, and to identify preferential flow. Laboratory tests were carried out using a soil flume where different scenarios were tested. Heated water was used to create a temperature gradient on the soil surface and high-resolution soil surface thermal imaging were obtained using a portable infrared camera. The technique was tested using soils with different permeability. The proposed technique successfully allows us to identify different soil surface permeability and to visualise preferential flows.

Using thermal tracers to estimate flow velocities of shallow flows: laboratory and field experiments

Abstract Accurate measurement of shallow flows is important for hydraulics, hydrology and water resources management. The objective of this paper is to discuss a technique for shallow flow and overland flow velocity estimation that uses infrared thermography. Laboratory flumes and different bare, vegetated and paved field surfaces were used to test the technique. Results show that shallow flow surface velocities estimated using thermal tracers and infrared technology are similar to estimates obtained using the Acoustic Doppler Velocimeter; similar results were also obtained for overland flow velocity estimates using thermography, here comparing with the dye tracer technique. The thermographic approach revealed some potential as a flow visualization technique, and leaves space for future studies and research.

Modelling runoff on ceramic tile roofs using the kinematic wave equations

Generally, roofs are the best candidates for rainwater harvesting. In this context, the correct evaluation of the quantity and quality of runoff from roofs is essential to effectively design rainwater harvesting systems. This study aims to evaluate the performance of a kinematic wave based numerical model in simulating runoff on sloping roofs, by comparing the numerical results with the ones obtained from laboratory rainfall simulations on a real-scale Lusa ceramic tile roof. For all studied slopes, simulated discharge hydrographs had a good adjust to observed ones. Coefficient of determination and Nash-Sutcliffe efficiency values were close to 1.0. Particularly, peak discharges, times to peak, peak durations and runoff volumes were very well simulated.

Revisiting simple methods to estimate drop size distributions: a novel approach based on infrared thermography

Abstract The infrared thermography has been successfully applied as a tool for high resolution imaging in different hydrological studies. This exploratory experimental study aimed at evaluating the possibility of using infrared thermography to determine the diameter of raindrops. Rain samples are collected on a pre-heated acrylic board, which is exposed to rain during an instant, and thermograms are recorded. The area of the thermal stains (“signatures” of the raindrops) emerging on the board is measured and converted to drop diameters, applying a calibration equation. Diameters of natural raindrops estimated using this technique were compared with laser disdrometer measurements; the Nash-Sutcliffe efficiency coefficient was used for evaluating the match between the resulting histograms of drop size distribution. Results confirm the usefulness of this simple technique for sizing and counting raindrops, although it is unsatisfactory in light rain or drizzle.

Evaluation of tissue perfusion parameters and intravascular volume, emphasizing the inferior vena cava diameter and collapsibility

Echocardiography in critically ill patients enables diagnosis of a large number of cardiac conditions, including life-threatening ones. Intensivists can use it as a powerful diagnostic tool.

Washout of Fine Sand Particles From a Ceramic Tile Roof: Laboratory Experiments Under Simulated Rainfall

Roof runoff is an important source of urban stormwater and a main source of rainwater harvesting. Deposition of pollutants on rooftops can have a negative impact on runoff quality and, therefore, on harvested rainwater. Laboratory experiments with simulated rainfall were performed in order to study the washout of fine sand particles deposited on a ceramic tile roof, by runoff, considering the effect of the particle position, particle areal load, particle connectivity and roof slope. Results indicated that particle washout was influenced by the particle position on the roof; particle transport peak and transported mass was higher for the particle mass positions closer to the outlet. Increase in particle areal load decreased particle transport whereas particle connectivity had no effect on particle transport. However, roof slope was a dominant aspect in the particle washout; increase in roof slope greatly increased particle transport peak and transported mass. It also remarkably increased the first flush effect.