Experimental and Numerical Study on Inundation Flows in Urban Areas

2009 ◽  
pp. 246-251
Author(s):  
Yoshihisa Kawahara ◽  
Yasushi Ito ◽  
Tatsuhiko Uchida
Keyword(s):  
Urban Areas ◽  
Numerical Study

Tunnel performance during the Puebla-Mexico 19 September 2017 earthquake

2020 ◽  
Vol 36 (2_suppl) ◽  
pp. 288-313
Author(s):  
Juan M Mayoral ◽  
Gilberto Mosqueda ◽  
Daniel De La Rosa ◽  
Mauricio Alcaraz
Keyword(s):  
Mexico City ◽  
Seismic Performance ◽  
Urban Areas ◽  
Numerical Study ◽  
Three Dimensional ◽  
Frequency Content ◽  
Seismic Performance Evaluation ◽  
Ground Deformations ◽  
Under Construction ◽  
Observed Damage

Seismic performance of tunnels during earthquakes in densely populated areas requires assessing complex interactions with existing infrastructure such as bridges, urban overpasses, and metro stations, including low- to medium-rise buildings. This article presents the numerical study of an instrumented tunnel, currently under construction on stiff soils, located in the western part of Mexico City, during the Puebla-Mexico 19 September 2017 earthquake. Three-dimensional finite difference models were developed using the software FLAC3D. Initially, the static response of the tunnel was evaluated accounting for the excavation technique. Then, the seismic performance evaluation of the tunnel was carried out, computing ground deformations and factors of safety, considering soil nonlinearities. Good agreement was observed between predicted and observed damage during post-event site observations. Once the soundness of the numerical model was established, a numerical study was undertaken to investigate the effect of frequency content in tunnel-induced ground motion incoherence for tunnels built in cemented stiff soils. A series of strong ground motions recorded during normal and subduction events were used in the simulations, considering a return period of 250 years, as recommended in the Mexico City building code. From the results, it was concluded that the tunnel presence leads to important frequency content modification in the tunnel surroundings which can affect low- to mid-rise stiff structures located nearby. This important finding must be taken into account when assessing the seismic risk in highly populated urban areas, such as Mexico City.

Computational Investigation of a Shrouded Vertical Axis Wind Turbine

2016 ◽  
Author(s):  
K. Vafiadis ◽  
H. Fintikakis ◽  
I. Zaproudis ◽  
A. Tourlidakis
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Urban Areas ◽  
Numerical Study ◽  
Flow Analysis ◽  
Vertical Axis ◽  
Green Energy ◽  
Vertical Axis Wind Turbine ◽  
Wide Range ◽  
Small Wind Turbines

In urban areas, it is preferable to use small wind turbines which may be integrated to a building in order to supply the local grid with green energy. The main drawback of using wind turbines in urban areas is that the air flow is affected by the existence of nearby buildings, which in conjunction with the variation of wind speed, wind direction and turbulence may adversely affect wind energy extraction. Moreover, the efficiency of a wind turbine is limited by the Betz limit. One of the methods developed to increase the efficiency of small wind turbines and to overcome the Betz limit is the introduction of a converging – diverging shroud around the turbine. Several researchers have studied the effect of shrouds on Horizontal Axis Wind Turbines, but relatively little research has been carried out on shroud augmented Vertical Axis Wind Turbines. This paper presents the numerical study of a shrouded Vertical Axis Wind Turbine. A wide range of test cases, were examined in order to predict the flow characteristics around the rotor, through the shroud and through the rotor – shroud arrangement using 3D Computational Fluid Dynamics simulations. The power output of the shrouded rotor has been improved by a factor greater than 2.0. The detailed flow analysis results showed that there is a significant improvement in the performance of the wind turbine.

scholarly journals EVALUATION OF THE POUNDING FORCES DURING EARTHQUAKE USING EXPLICIT DYNAMIC TIME INTEGRATION METHOD

2017 ◽  
Vol 13 (3) ◽  
pp. 21-39
Author(s):  
George Bogdan Nica ◽  
Andrei Gheorghe Pricopie
Keyword(s):  
Urban Areas ◽  
Integration Method ◽  
Numerical Study ◽  
Equations Of Motion ◽  
Time Integration ◽  
Nonlinear Behavior ◽  
Implicit Time ◽  
Time Integration Method ◽  
Nonlinear Viscoelastic ◽  
Weak Structure

Abstract Pounding effects during earthquake is a subject of high significance for structural engineers performing in the urban areas. In this paper, two ways to account for structural pounding are used in a MATLAB code, namely classical stereomechanics approach and nonlinear viscoelastic impact element. The numerical study is performed on SDOF structures acted by ELCentro recording. While most of the studies available in the literature are related to Newmark implicit time integration method, in this study the equations of motion are numerical integrated using central finite difference method, an explicit method, having the main advantage that in the displacement at the ith+1 step is calculated based on the loads from the ith step. Thus, the collision is checked and the pounding forces are taken into account into the equation of motion in an easier manner than in an implicit integration method. First, a comparison is done using available data in the literature. Both linear and nonlinear behavior of the structures during earthquake is further investigated. Several layout scenarios are also investigated, in which one or more weak buildings are adjacent to a stiffer building. One of the main findings in this paper is related to the behavior of a weak structure located between two stiff structures.

scholarly journals Numerical Study of the Interaction between Oasis and Urban Areas within an Arid Mountains-Desert System in Xinjiang, China

Atmosphere ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 85
Author(s):  
Peng Cai ◽  
Rafiq Hamdi ◽  
Huili He ◽  
Geping Luo ◽  
Jin Wang ◽  
...  
Keyword(s):  
Land Surface ◽  
Urban Areas ◽  
Climate Model ◽  
Numerical Study ◽  
Urban Expansion ◽  
Regional Climate ◽  
Maximum Effect ◽  
Local Circulation ◽  
Urban Rural ◽  
The Impact

The rapid oasis expansion and urbanization that occurred in Xinjiang province (China) in the last decades have greatly modified the land surface energy balance and influenced the local circulation under the arid mountains-plain background system. In this study, we first evaluated the ALARO regional climate model coupled to the land surface scheme SURFEX at 4 km resolution using 53 national climatological stations and 5 automatic weather stations. We found that the model correctly simulates daily and hourly variation of 2 m temperature and relative humidity. A 4-day clear sky period has been chosen to study both local atmospheric circulations and their mutual interaction. Observations and simulations both show that a low-level divergence over oasis appears between 19:00 and 21:00 Beijing Time when the background mountain-plain wind system is weak. The model simulates a synergistic interaction between the oasis-desert breeze and urban-rural breeze from 16:00 until 22:00 with a maximum effect at 20:00 when the downdraft over oasis (updraft over urban) areas increases by 0.8 (0.4) Pa/s. The results show that the oasis expansion decreases the nocturnal urban heat island in the city of Urumqi by 0.8 °C, while the impact of urban expansion on the oasis cold island is negligible.

Numerical Study of Vertical Axis Wind Turbine Rotor Configuration

2013 ◽  
Vol 859 ◽  
pp. 28-32
Author(s):  
Yi Mei ◽  
Jian Jun Qu ◽  
Xiao Ya Liu
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Numerical Study ◽  
Vertical Axis ◽  
Turbine Rotor ◽  
Radius Ratio ◽  
Speed Ratio ◽  
Wind Condition ◽  
Vertical Axis Wind Turbine ◽  
Power Performance

This paper presents a numerical study of a vertical axis wind rotor configuration. Below constant wind condition 8m/s, rotor power performance was investigated over variable turbine configurations. Illustrated by the simulation, increasing rotor cord to radius ratio or blade numbers will enhance the generation of vortexes and flow separation on blades, leading to the significant degradation of turbine performance. It can be conclude form the numerical analysis, a vertical axis wind turbine with high height to radius ratio applied in urban areas experienced better performance when operating in optimal tip speed ratio, with rotor cord to radius ratio between 0.2 and 0.4 and blade number of 3 or 4.

scholarly journals The role of heterogeneous lithology in a glaciofluvial deposit on unsaturated preferential flow – a numerical study

2017 ◽  
Vol 65 (3) ◽  
pp. 209-221 ◽  
Author(s):  
Erij Ben Slimene ◽  
Laurent Lassabatere ◽  
Jiří Šimůnek ◽  
Thierry Winiarski ◽  
Remy Gourdon
Keyword(s):  
Urban Areas ◽  
Hydraulic Properties ◽  
Preferential Flow ◽  
Numerical Study ◽  
Full Characterization ◽  
Capillary Barriers ◽  
Flow Pathways ◽  
Preferential Flow Pathways

AbstractAn understanding of preferential flow in the vadose zone is crucial for the prediction of the fate of pollutants. Infiltration basins, developed to mitigate the adverse effects of impervious surfaces in urban areas, are established above strongly heterogeneous and highly permeable deposits and thus are prone to preferential flow and enhanced pollutant transport. This study numerically investigates the establishment of preferential flow in an infiltration basin in the Lyon suburbs (France) established over a highly heterogeneous glaciofluvial deposit covering much of the Lyon region. An investigation of the soil transect (13.5 m long and 2.5 m deep) provided full characterization of lithology and hydraulic properties of present lithofacies. Numerical modeling with the HYDRUS-2D model of water flow in the transect was used to identify the effects of individual lithofacies that constitute the deposit. Multiple scenarios that considered different levels of heterogeneity were evaluated. Preferential flow was studied for several values of infiltration rates applied after a long dry period. The numerical study shows that the high contrast in hydraulic properties of different lithofacies triggers the establishment of preferential flow (capillary barriers and funneled flow). Preferential flow develops mainly for low water fluxes imposed at the surface. The role of individual lithofacies in triggering preferential flow depends on their shapes (layering versus inclusions) and their sizes. While lenses and inclusions produce preferential flow pathways, the presence of the surface layer has no effect on the development of preferential flow and it only affects the effective hydraulic conductivity of the heterogeneous transect.

Numerical Study of Thermal Comfort with the Effects of Canopy Transparency

2014 ◽  
Vol 919-921 ◽  
pp. 1677-1680
Author(s):  
Choul Woong Kwon ◽  
Sung Woo Shin
Keyword(s):  
Thermal Comfort ◽  
Urban Areas ◽  
Thermal Environment ◽  
Numerical Study ◽  
Complex Surface ◽  
Outdoor Thermal Comfort ◽  
Thermal Indices ◽  
Physiological Equivalent Temperature ◽  
Thermal Index ◽  
Radiation Fluxes

Several complex thermal indices (e.g. PMV and PET) were developed in the last decades to describe the quantify the thermal environment of humans and the energy fluxes between body and environment. Compared to open spaces the complex surface structure of urban areas creates an environment with special microclimatic characteristics, which have a dominant effect on the energy balance of the human body. In this study, outdoor thermal comfort conditions are examined through numerical model with different transparency ratios in canopy. The intensity of radiation fluxes is dependent on several factors, such as orientation, size and transparency of canopy. Special emphasis is given to the human-biometeorological assessment of the microclimate of building element (canopy) through the application of the thermal index PET (Physiological Equivalent Temperature). The analysis is carried out by the utilization of Ecotect and RayMan software.

scholarly journals Maintenance and risk management of rockfall protection net fences through numerical study of deteriorations

2016 ◽  
Author(s):  
Andrea Luciani ◽  
Monica Barbero ◽  
Daniele Martinelli ◽  
Daniele Peila
Keyword(s):  
Risk Management ◽  
Risk Analysis ◽  
Numerical Modelling ◽  
Urban Areas ◽  
Risk Mitigation ◽  
Numerical Study ◽  
Maintenance Planning ◽  
Mountainous Areas ◽  
Protection Systems ◽  
Rockfall Protection

Abstract. Rockfall protection net fences are key protection systems in mountainous areas worldwide to ensure the safety of infrastructures, roads and urban areas against rockfall. Management of the maintenance of rockfall protection net fences is fundamental for public administrations in order to guarantee risk mitigation. This paper deals with the assessment of the installation problems and deterioration of rockfall protection net fences, using numerical modelling in order to evaluate the influence of these issues on their behaviour. A percentage of the residual efficiency is assessed as a useful tool for risk analysis and maintenance planning.

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