The Experts below are selected from a list of 21264 Experts worldwide ranked by ideXlab platform
Jan Carmeliet - One of the best experts on this subject based on the ideXlab platform.
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coupling of physical phenomena in urban microclimate a model integrating air flow wind driven Rain radiation and transport in building materials
urban climate, 2017Co-Authors: A Kubilay, Dominique Derome, Jan CarmelietAbstract:Abstract Building materials play an important role in the absorption, transport and storage of heat and moisture in the built environment. A fully-integrated urban microclimate model is proposed, which solves for wind flow and for the transport of heat and moisture in the air and building materials. The model includes long-wave and short-wave radiative exchange between surfaces and the distribution of wind-driven Rain Intensity. Transport in air and building materials are coupled in such a way that the steady Reynolds-averaged Navier-Stokes (RANS) is solved iteratively with the unsteady heat and moisture transfer in building materials. The proposed approach provides the information required for analyzing different contributions of convective cooling, sensible heat transfer due to Rain, evaporation, in addition to the thermal storage throughout the day. This approach is demonstrated with a case study investigating the impact of Rain deposition on an isolated three-dimensional street canyon lined with porous building materials. The study shows different rate of evaporation and duration of evaporative cooling for a change in wind speed during a Rain event. The distribution of wind-driven Rain particularly influences the spatial and temporal distribution of surface and air temperatures. A significant influence of neighboring surfaces is found on the surface temperatures.
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wind driven Rain as a boundary condition for ham simulations analysis of simplified modelling approaches
Building and Environment, 2007Co-Authors: Hans Janssen, Jan Carmeliet, Bje Bert Blocken, Staf RoelsAbstract:While the numerical simulation of moisture transfer inside building components is currently undergoing standardisation, the modelling of the atmospheric boundary conditions has received far less attention. This article analyses the modelling of the wind-driven-Rain load on building facades by partial simplification of a complex CFD-based method along the lines of the European Standard method. The results indicate that the directional dependence of the wind-driven-Rain coefficient is not of substantial importance. A constant wind-driven-Rain coefficient appears to be an oversimplification though: the full variability with the perpendicular wind speed and horizontal Rain Intensity should be preserved, where feasible, for improved estimations of the moisture transfer in building components. In the concluding section, it is moreover shown that the dependence of the surface moisture transfer coefficient on wind speed has an equally important influence on the moisture transfer in building components.
Majid Mahmoodabadi - One of the best experts on this subject based on the ideXlab platform.
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effects of Rain Intensity slope gradient and particle size distribution on the relative contributions of splash and wash loads to Rain induced erosion
Geomorphology, 2016Co-Authors: Majid Mahmoodabadi, Sara Arjmand SajjadiAbstract:Abstract Soil erosion during Rainfall is a complex phenomenon resulting from detachment by Raindrop impact and overland flow. The objective of this study is to investigate the transportation rate of splash load (SL) and that of wash load (WL) and their relative contributions to the Rain-induced erosion rate affected by Rain Intensity, slope gradient and particle size distribution. A total of 60 simulation runs were carried out using a detachment tray under simulated Rainfall with no inflow. The experiments were done on two soil samples (aggregate sizes finer than 2 and 4.75 mm) from an agricultural land use at different Rain intensities (57 and 80 mm h− 1) and varying slope gradients (0.5%, 2.5%, 5%, 10%, and 20%). Under unsteady state conditions, WL showed relatively high dependency on slope gradient, whereas approaching steady state conditions, nearly similar values of WL occurred at different slopes. SL and WL increased with increasing Rain Intensity and slope gradient, implying the importance of Rain-induced erosion on bare agriculture lands especially at steeper slopes. The ratio of WL/SL decreased when slope gradient increased; however, WL increased more significantly than SL as soil aggregates became finer. The result indicates that at all the slope gradients, WL was much larger than SL, indicating that wash load significantly contributes to the Rain-induced erosion in the agricultural soil. Furthermore, with increasing slope gradient, the contribution of wash load to Rain-induced erosion decreased, while it was greater in the soil containing finer aggregates. Also, with increasing Rain Intensity at lower slope gradients ( 10%). The finding of this study revealed that the Rain-induced erosion was transport-limited at the gentler slopes, whereas at the steeper slopes, it shifted to detachment-limited conditions.
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sediment concentration and hydraulic characteristics of Rain induced overland flows in arid land soils
Journal of Soils and Sediments, 2015Co-Authors: Sara Arjmand Sajjadi, Majid MahmoodabadiAbstract:Purpose Rain-induced overland flow involves the detachment of soil particles by Raindrop impact and the transportation by the resultant overland flow. The purpose of this study was to investigate the relationship between sediment concentration and different hydraulic parameters including flow depth, flow velocity, shear stress, stream power, and unit stream power. The effects of soil particle size distribution, Rain Intensity, and slope steepness on measured sediment concentration in Rain-induced sheet flow were also examined.
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aggregate breakdown and surface seal development influenced by Rain Intensity slope gradient and soil particle size
Solid Earth, 2014Co-Authors: Arjmand S Sajjadi, Majid MahmoodabadiAbstract:Abstract. Aggregate breakdown is an important process which controls infiltration rate (IR) and the availability of fine materials necessary for structural sealing under Rainfall. The purpose of this study was to investigate the effects of different slope gradients, Rain intensities and particle size distributions on aggregate breakdown and IR to describe the formation of surface seal. To address this issue, 60 experiments were carried out in a 35 × 30 × 10 cm detachment tray using a Rainfall simulator. By sieving a sandy loam soil, two sub-samples with different maximum aggregate sizes of 2 mm (Dmax2 mm) and 4.75 mm (Dmax4.75 mm) were prepared. The soils were exposed to two different Rain intensities (57 and 80 mm h−1) on several slopes (0.5, 2.5, 5, 10 and 20%) each at three replicates. The result showed that for all slope gradients and Rain intensities, the most fraction percentages in soils Dmax2 and Dmax4.75 mm were in the finest size classes of 0.02 and 0.043 mm, respectively. The soil containing finer aggregates exhibited higher transportability of pre-detached material than the soil containing larger aggregates. Also, IR increased with increasing slope gradient, Rain Intensity and aggregate size under unsteady state conditions because of less development of surface seal. However, under steady state conditions, no significant relationship was found between slope and IR. The findings of this study revealed the importance of Rain Intensity, slope steepness and soil aggregate size on aggregate breakdown and seal formation, which can control infiltration rate and the consequent runoff and erosion rates.
Sara Arjmand Sajjadi - One of the best experts on this subject based on the ideXlab platform.
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effects of Rain Intensity slope gradient and particle size distribution on the relative contributions of splash and wash loads to Rain induced erosion
Geomorphology, 2016Co-Authors: Majid Mahmoodabadi, Sara Arjmand SajjadiAbstract:Abstract Soil erosion during Rainfall is a complex phenomenon resulting from detachment by Raindrop impact and overland flow. The objective of this study is to investigate the transportation rate of splash load (SL) and that of wash load (WL) and their relative contributions to the Rain-induced erosion rate affected by Rain Intensity, slope gradient and particle size distribution. A total of 60 simulation runs were carried out using a detachment tray under simulated Rainfall with no inflow. The experiments were done on two soil samples (aggregate sizes finer than 2 and 4.75 mm) from an agricultural land use at different Rain intensities (57 and 80 mm h− 1) and varying slope gradients (0.5%, 2.5%, 5%, 10%, and 20%). Under unsteady state conditions, WL showed relatively high dependency on slope gradient, whereas approaching steady state conditions, nearly similar values of WL occurred at different slopes. SL and WL increased with increasing Rain Intensity and slope gradient, implying the importance of Rain-induced erosion on bare agriculture lands especially at steeper slopes. The ratio of WL/SL decreased when slope gradient increased; however, WL increased more significantly than SL as soil aggregates became finer. The result indicates that at all the slope gradients, WL was much larger than SL, indicating that wash load significantly contributes to the Rain-induced erosion in the agricultural soil. Furthermore, with increasing slope gradient, the contribution of wash load to Rain-induced erosion decreased, while it was greater in the soil containing finer aggregates. Also, with increasing Rain Intensity at lower slope gradients ( 10%). The finding of this study revealed that the Rain-induced erosion was transport-limited at the gentler slopes, whereas at the steeper slopes, it shifted to detachment-limited conditions.
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sediment concentration and hydraulic characteristics of Rain induced overland flows in arid land soils
Journal of Soils and Sediments, 2015Co-Authors: Sara Arjmand Sajjadi, Majid MahmoodabadiAbstract:Purpose Rain-induced overland flow involves the detachment of soil particles by Raindrop impact and the transportation by the resultant overland flow. The purpose of this study was to investigate the relationship between sediment concentration and different hydraulic parameters including flow depth, flow velocity, shear stress, stream power, and unit stream power. The effects of soil particle size distribution, Rain Intensity, and slope steepness on measured sediment concentration in Rain-induced sheet flow were also examined.
L G Lanza - One of the best experts on this subject based on the ideXlab platform.
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high resolution performance of catching type Rain gauges from the laboratory phase of the wmo field intercomparison of Rain Intensity gauges
Atmospheric Research, 2009Co-Authors: L G Lanza, Luigi StagiAbstract:Abstract The WMO Field Intercomparison of Rainfall Intensity (RI) Gauges started on October, 1st 2007 at Vigna di Valle (Italy) and was concluded in May 2009. Those catching type instruments, out of the selected Rain gauges based on various measuring principles, and the four Rain gauges selected as reference instruments to be installed in a pit, were preliminarily calibrated in the laboratory before their final installation at the Field Intercomparison site. The recognized WMO laboratory at the University of Genoa was involved in this task, using the same standard tests adopted for the previously held WMO Laboratory Intercomparison of RI gauges. Further tests were performed to investigate the one-minute performance of the involved instruments. The present paper deals with basically Tipping-Bucket Rain gauges (TBRs) and Weighing Gauges (WGs), using results from tests performed under constant flow rates in laboratory conditions. The objective of this initial phase of the Intercomparison was to single out the counting errors associated with each instrument, so as to help the understanding of the measured differences between instruments in the field during the second phase. Results and comments on the preliminary laboratory calibration exercise are reported in this paper together with their implications for the analysis of the outcome of the Intercomparison in the Field.
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the wmo field intercomparison of Rain Intensity gauges
Atmospheric Research, 2009Co-Authors: L G Lanza, Emanuele VuerichAbstract:Abstract The first Field Intercomparison of Rainfall Intensity (RI) gauges was organised by WMO (the World Meteorological Organisation) from October 2007 to April 2009 in Vigna di Valle, Rome (Italy). The campaign is held at the Centre of Meteorological Experimentations (ReSMA) of the Italian Meteorological Service. A group of 30 previously selected Rain gauges based on different measuring principles are involved in the Intercomparison. Installation of the instruments in the field was preceded by the laboratory calibration of all submitted catching-type Rain gauges at the University of Genoa. Additional meteorological sensors (ancillary information) and the observations and measurements performed by the Global Climate Observing System/Global Atmosphere Watch (GCOS/GAW) meteorological station of Vigna di Valle were analyzed as metadata. All catching-type gauges were tested after installation using a portable calibration device specifically developed at the University of Genoa, simulating an ordinary calibration inspection in the field. This paper is dedicated to the summary of preliminary results of the Intercomparison measurements. It offers a view on the main achievements expected from the Intercomparison in evaluating the performance of the instruments in field conditions. Comparison of several Rain gauges demonstrated the possibility to evaluate the performance of RI gauges at one-minute resolution in time, as recommended by the WMO Commission for Instruments and Methods of Observations (WMO-CIMO). Results indicate that synchronised tipping-bucket Rain gauges (TBR), using internal correction algorithms, and weighing gauges (WG) with improved dynamic stability and short step response are the most accurate gauges for one-minute RI measurements, since providing the lowest measurement uncertainty with respect to the assumed working reference.
S Fuzzi - One of the best experts on this subject based on the ideXlab platform.
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precipitation scavenging coefficient influence of measured aerosol and Raindrop size distributions
Atmospheric Environment, 2000Co-Authors: Mihaela Mircea, Sabina Stefan, S FuzziAbstract:Precipitation scavenging coefficients, widely used in pollution studies, are derived from microphysical parameterisations of aerosol particles and Raindrop populations and parameterisations of their interactions. The present study investigates the effects of measured aerosol and Raindrop size distributions in a microphysical polydisperse framework. The interactions between aerosol and Raindrops parameterised as collision efficiency are explicitly included to account for Brownian diffusion, inertial impaction and interception. Estimated values of the polydisperse scavenging coefficients exhibit variations of orders of magnitude depending on the aerosol type and almost no variation with the Raindrop size distributions. For practical use, linear relationships between the scavenging coefficients and Rain Intensity for different aerosol types are derived.