The effects of wind velocity and building geometry on air change efficiency in light shafts: Case studies

2016 ◽  
Vol 38 (1) ◽  
pp. 5-20 ◽  
Author(s):  
Miguel Ángel Padilla-Marcos ◽  
Jesús Feijó-Muñoz ◽  
Alberto Meiss
Keyword(s):  
Wind Velocity ◽  
Natural Ventilation ◽  
Efficiency Index ◽  
Practical Applications ◽  
Building Shape ◽  
Building Geometry ◽  
Outdoor Environments ◽  
Wind Velocities ◽  
External Conditions ◽  
Light Shaft

The evaluation of the air quality in light shafts requires a specific study of its air renewal ability due to building shape, dimensions and other external conditions. This research has studied the capacity of light shafts to provide natural ventilation through the air change efficiency concept. A methodology based on the limitation of the computational urban domain is used to adapt the indoor air change efficiency index for outdoor environments. Numerical simulations were performed using CFD and a model that was experimentally validated. The aim is to evaluate the effect of the centreline building width and light shaft dimensions in the air change quality within several wind climates. Results would provide a numerically proven tool for designers, summarised in some design-based strategies in order to select which one improves the air change quality. The results indicate that the light shaft dimension perpendicular to the wind direction has a negligible effect on efficiency. For the range of wind velocities studied (0.75–9.00 m/s), the efficiency decreases at higher velocities, up to −7.41% with respect to the mean. For variations in the wind velocity and the centreline building width, a mean variation of ± 18.77% in the efficiency is obtained. Practical applications: The present methodology defines a proceeding to numerically evaluate the air change efficiency in light shafts inside different dimensional cases of buildings within several urban wind conditions.

scholarly journals The natural ventilation of unheated ‘closed rooms’

1946 ◽  
Vol 44 (5) ◽  
pp. 314-325 ◽  
Author(s):  
J. B. Carne
Keyword(s):  
Experimental Method ◽  
Wind Velocity ◽  
Experimental Work ◽  
Simultaneous Measurement ◽  
Natural Ventilation ◽  
Relative Efficacy ◽  
General Manager ◽  
Influx Rate ◽  
Physical Laboratory ◽  
Wind Velocities

The experimental method for, and analysis of, more than 300 determinations of air influx rates into two unheated ‘closed rooms’ of opposite aspects each fitted (a) with wall grating, or (b) with flue, are described. The average relative efficacy for all observed wind velocities of (a) of 50 sq.in. to (b) of 15 sq.in., so far as facilitating natural ventilation in the rooms used, is found to be 1·0. The analysis reveals definite and complex relations between influx rate and wind velocity. A correlation is made with data from other sources, principally photographs of the flow forms of air streaming past grounded house models, and a theory is advanced to explain the broad features of the observations. Comparison with similar published work is made, and the fundamental necessity of simultaneous measurement of the speed and direction of the main wind stream is stressed. The advantage of the flue and the importance of openings, other than those in the room concerned, are pointed out.The author wishes to record that the investigation was commenced at the instigation of Mr Dean Chandler, to whom he is indebted for en-couragement to publish the results of the further examination of the data obtained. He desires also to acknowledge the enthusiastic interest in the experimental work which his colleagues of the Physical Laboratory displayed throughout the investigation.The measurements of the wind velocity, so essential to the completeness of the observations, frequently necessitated the scaling of roofs in snow, rain and gale, yet at no time were they neglected.The author thanks Dr E. V. Evans, General Manager and Director of the South Metropolitan Gas Co., for granting permission to publish the paper.

Effects of different wind directions on ventilation of surrounding areas of two generic building configurations in Hong Kong

2021 ◽  
pp. 1420326X2110160
Author(s):  
Kai Yip Lee ◽  
Cheuk Ming Mak
Keyword(s):  
Wind Velocity ◽  
Natural Ventilation ◽  
Urban Environments ◽  
Air Pressure ◽  
Pressure Distributions ◽  
Air Intake ◽  
Dynamics Simulations ◽  
Surrounding Areas ◽  
Effective Use ◽  
Velocity Zone

This study investigated effects of incident wind angles on wind velocity distributions in wakes of two generic building configurations, namely, ‘T’- and ‘+’-shaped, and the air pressure distributions along their leeward walls by using computational fluid dynamics simulations. Results show that when the wind approaches laterally (90°) (vs. when the wind is direct (0°)), the downwind length and maximum bilateral width of the low-wind velocity zone in the wake of ‘T’-shaped building decrease by 11.5% and 37.9%, respectively. When the incident wind is oblique (45°) (vs. when it is direct), the length and width of this low-wind velocity zone in the wake of ‘+’-shaped building decrease by 15.0% and 30.9%, respectively. Furthermore, results show that the air pressure on the leeward walls of the ‘T’- and ‘+’-shaped buildings gradually decreases along with the building height. The resulting low-wind conditions on upper floors of buildings reduce the fresh air intake of their leeward units utilizing natural ventilation. It is particularly apparent in the case of direct approaching wind. Thus, the appropriate selection of building configurations and their orientations allows for the most effective use of wind to enhance ventilation in indoor and urban environments.

scholarly journals Decentralized 3D Collision Avoidance for Multiple UAVs in Outdoor Environments

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4101 ◽  
Author(s):  
Eduardo Ferrera ◽  
Alfonso Alcántara ◽  
Jesús Capitán ◽  
Angel Castaño ◽  
Pedro Marrón ◽  
...  
Keyword(s):  
Collision Avoidance ◽  
System Integration ◽  
Field Experiments ◽  
Positioning Systems ◽  
Wind Gusts ◽  
Aerial Vehicles ◽  
Multiple Uavs ◽  
Outdoor Environments ◽  
External Conditions ◽  
Field Experimentation

The use of multiple aerial vehicles for autonomous missions is turning into commonplace. In many of these applications, the Unmanned Aerial Vehicles (UAVs) have to cooperate and navigate in a shared airspace, becoming 3D collision avoidance a relevant issue. Outdoor scenarios impose additional challenges: (i) accurate positioning systems are costly; (ii) communication can be unreliable or delayed; and (iii) external conditions like wind gusts affect UAVs’ maneuverability. In this paper, we present 3D-SWAP, a decentralized algorithm for 3D collision avoidance with multiple UAVs. 3D-SWAP operates reactively without high computational requirements and allows UAVs to integrate measurements from their local sensors with positions of other teammates within communication range. We tested 3D-SWAP with our team of custom-designed UAVs. First, we used a Software-In-The-Loop simulator for system integration and evaluation. Second, we run field experiments with up to three UAVs in an outdoor scenario with uncontrolled conditions (i.e., noisy positioning systems, wind gusts, etc). We report our results and our procedures for this field experimentation.

The Green Building Environment of the Gymnasium

2018 ◽  
Vol 878 ◽  
pp. 202-209 ◽  
Author(s):  
Feng Qian ◽  
Li Yang
Keyword(s):  
Natural Ventilation ◽  
Residential Buildings ◽  
Green Building ◽  
Residential Area ◽  
Simulation Software ◽  
Living Environment ◽  
Outdoor Environment ◽  
Residential Areas ◽  
Outdoor Environments ◽  
Area Planning

The natural ventilation of residential areas has placed more and more emphasis on residential area planning, according to the relationship between natural ventilation environments and the layout of architecture, we can reduce the energy consumption and the adverse effect of wind outdoors, improve the living environment and quality of life, making harmony between human and the nature. In this paper, we use Air-Pak to simulate the wind environment of residential areas. Through analyzing and simulating the air field which forms when the wind blows around the residential buildings by Air-Pak, we explain the advantage of the combination of computer simulation software and residential area planning. And we give some advice to the layout of the outdoor environment early in the residential planning area by the simulation of outdoor environments of buildings.

scholarly journals Parametric design analysis of elliptical shroud profile

AIMS Energy ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1147-1169
Author(s):  
Salih Nawaf Akour ◽  
◽  
Mahmoud Azmi Abo Mhaisen
Keyword(s):  
Wind Turbine ◽  
Wind Velocity ◽  
Parametric Design ◽  
Large Family ◽  
Design Analysis ◽  
Average Wind ◽  
Wind Velocities ◽  
Inlet Length ◽  
Commercial Software Package ◽  
Exact Shape

<abstract> <p>Parametric design analysis for Eccentric Rotated Ellipsoid (ERE) shroud profile is conducted whereas the design model is validated experimentally. A relation between shroud inlet, length and exit diameter is established, different ratios related to the wind turbine diameter are introduced, and solution for different ERE family curves that passes on the inlet, throat, and exit points is studied. The performance of the ERE shroud is studied under different wind velocities ranging from 5–10 m/s.</p> <p>The method used in creating the shroud profile is by solving the ERE curve equations to generate large family of solutions. The system is modeled as axisymmetric system utilizing commercial software package. The effect of the parameters; shroud length, exit diameter, inlet diameter, turbine position with respect to the shroud throat, and wind velocity are studied. An optimum case for each shroud length, exit diameter and location of the shroud with respect to the wind turbine throat axis are achieved.</p> <p>The simulation results show an increase in the average wind velocity by 1.63 times of the inlet velocity. This leads to a great improvement in the wind turbine output power by 4.3 times of bare turbine. One of the achieved optimum solutions for the shroud curves has been prototyped for experimental validation. The prototype has been manufactured using 3D printing technology which provides high accuracy in building the exact shape of shroud design curve. The results show very good agreement with the experimental results.</p></abstract>

scholarly journals Three-Dimensional Simulation of Wind-Driven Ventilation Through a Windcatcher With Different Inlet Designs

2019 ◽  
Vol 12 (4) ◽  
Author(s):  
Peter Abdo ◽  
Rahil Taghipour ◽  
B. Phuoc Huynh
Keyword(s):  
Wind Speed ◽  
Average Velocity ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Three Dimensional ◽  
Cfd Modeling ◽  
Ansys Fluent ◽  
Wind Velocities ◽  
Dimensional Simulation ◽  
Convergent Inlet

Abstract Windcatcher is an effective natural ventilation system, and its performance depends on several factors including wind speed and wind direction. It provides a comfortable and healthy indoor environment since the introduced fresh air decreases the moisture content and reduces the pollutant concentration. Since the wind speed and its direction are generally unpredictable, it is important to use special inlet forms and exits to increase the efficiency of a windcatcher. In this study, computational fluid dynamics (CFD) modeling is implemented using ansys fluent to investigate the airflow entering a three-dimensional room through a windcatcher with different inlet designs. Three designs are studied which are a uniform inlet, a divergent inlet, and a bulging-convergent inlet. The airflow pattern with all inlets provided adequate ventilation through the room. With all the applied wind velocities (1, 2, 3, and 6 m/s) at the domain's inlet, the divergent inlet shape has captured the highest airflow through the room and provided higher average velocity at 1.2 m high enhancing the thermal comfort where most of the human occupancy occurs. With 6 m/s wind velocity, the divergent inlet has captured 2.55% more flow rate compared to the uniform inlet and 4.70% compared to the bulging-convergent inlet, and it has also provided an average velocity at 1.2 m high in the room of 7.16% higher than the uniform inlet and 8.44% higher than the bulging-convergent inlet.

Green’s function–based surrogate model for windfields using limited samples

2017 ◽  
Vol 42 (3) ◽  
pp. 164-176 ◽  
Author(s):  
Joshua Paul Marshall ◽  
Joseph David Richardson ◽  
Carlos Jose Montalvo
Keyword(s):  
Green’S Function ◽  
Wind Velocity ◽  
Green's Function ◽  
Surrogate Model ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Fast Method ◽  
Three Dimensional Model ◽  
Wind Velocities ◽  
Wind Measurements

There exists many applications for which wind-velocity is desired over a three-dimensional space. The vector field associated with these wind velocities is known as a “windfield” or “velocity-windfield.” The present work provides a fast method to characterize windfields. The approach uses the free-space Green’s function for potential theory as an inexpensive surrogate model in lieu of either complicated physics-based models or other types of surrogate models, both of which require volumetric discretizations for the three-dimensional case. Using the gradient of the third Green’s identity, the wind-velocity in the interior of a domain is entirely characterized by a surface discretization while still providing a three-dimensional model. The unknown densities on the surface are determined from enforcement of the interior form of the identity at arbitrary points coinciding with wind measurements taken by unmanned aerial vehicles. Numerical results support the feasibility of the method.

scholarly journals Thermal Environment Design of Outdoor Spaces by Examining Redevelopment Buildings Opposite Central Osaka Station

Climate ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 143 ◽  
Author(s):  
Hideki Takebayashi
Keyword(s):  
Solar Radiation ◽  
Wind Velocity ◽  
Thermal Environment ◽  
Heat Budget ◽  
Environment Design ◽  
Building Shape ◽  
Outdoor Spaces ◽  
Outdoor Space ◽  
Typical Summer ◽  
Radiant Temperature

Thermal environmental design in an outdoor space is discussed by focusing on the proper selection and arrangement of buildings, trees, and covering materials via the examination of redevelopment buildings in front of Central Osaka Station, where several heat island countermeasure technologies have been introduced. Surface temperatures on the ground and wall were calculated based on the surface heat budget equation in each 2 m size mesh of the ground and building wall surface. Incident solar radiation was calculated using ArcGIS and building shape data. Mean radiant temperature (MRT) of the human body was calculated using these results. Distribution of wind velocity was calculated by computational fluid dynamics (CFD) reproducing buildings, obstacles, trees, and the surroundings. The effect of MRT on SET* was greater than that of wind velocity at 13:00 and 17:00 on a typical summer day. SET* reduction was the highest by solar radiation shading, followed by surface material change and ventilation. The largest ratio of the area considered for the thermal environment was 83% on Green Garden, which consists of 44% of building shade, 21% of tree shade, 7% of water surface, and 11% of green cover. It is appropriate to consider the thermal environment design of outdoor space in the order of shade by buildings, shading by trees, and improvement of surface materials.

scholarly journals Method for Determining Neutral Wind Velocity Vectors Using Measurements of Internal Gravity Wave Group and Phase Velocities

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 546 ◽  
Author(s):  
Andrey V. Medvedev ◽  
Konstantin G. Ratovsky ◽  
Maxim V. Tolstikov ◽  
Roman V. Vasilyev ◽  
Maxim F. Artamonov
Keyword(s):  
Group Velocity ◽  
Wind Velocity ◽  
Wave Vector ◽  
Velocity Vector ◽  
Internal Gravity Waves ◽  
Vertical Wind ◽  
New Method ◽  
Neutral Wind ◽  
Wind Velocities ◽  
Wind Measurements

This study presents a new method for determining a neutral wind velocity vector. The basis of the method is measurement of the group velocities of internal gravity waves. Using the case of the Boussinesq dispersion relation, we demonstrated the ability to measure a neutral wind velocity vector using the group velocity and wave vector data. An algorithm for obtaining the group velocity vector from the wave vector spectrum is proposed. The new method was tested by comparing the obtained winter wind pattern with wind data from other sources. Testing the new method showed that it is in quantitative agreement with the Fabry–Pérot interferometer wind measurements for zonal and vertical wind velocities. The differences in meridional wind velocities are also discussed here. Of particular interest were the results related to the measurement of vertical wind velocities. We demonstrated that two independent methods gave the presence of vertical wind velocities with amplitude of ~20 m/s. Estimation of vertical wind contribution to plasma drift velocity indicated the importance of vertical wind measurements and the need to take them into account in physical and empirical models of the ionosphere and thermosphere.

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