Impact of Enclosure Boundary Patterns and Lift-Up Design on Optimization of Summer Pedestrian Wind Environment in High-Density Residential Districts

A comfortable wind environment favors the sustainable development of urban residential districts and public health. However, the rapid growth of high-rise urban residential districts leads to low wind velocity environments in summer. This study examines the influence of enclosure boundary patterns and lift-up design on the wind environment and proposes an optimization strategy to improve the low wind velocity environment in residential districts in summer. A typical residential district in Hangzhou was selected; the average wind velocity, calm wind zone ratio and comfortable wind zone ratio were selected as the evaluation indexes. The wind environment for different enclosure boundary patterns and lift-up designs were obtained via computational fluid dynamics (CFD) simulations. The results indicate that the pedestrian wind environment is greatly improved in residential districts by reducing the height/width of the enclosure boundary, increasing the permeability rate and adopting a lift-up design in all buildings within residential districts. A combination of permeable railings and lift-up design is recommended; this can increase the average wind velocity and the ratio of comfortable wind zones by 70% and 200%, respectively. This study provides practical guidelines for the optimization of a low wind velocity environment in Chinese high-density residential districts in summer.

Simulation of aeration of buildings erected on complex terrain

The problem of improving the environment by rational use of natural resources is currently very relevant. By means of theoretical and experimental metrological and aerodynamic studies, the infiltration processes between the internal and external air environment during the wind flow around buildings of buildings erected on complex terrain, as well as the adjacent territories of residential development, are established, which allows us to assess the heat loss and ventilation conditions of buildings under wind pressure. A model of the formation of the circulation zone for different geometric parameters of buildings, wind flow velocity and slope steepness is developed, which allows preliminary forecasting of the aeration regime of the adjacent territories. Zones of backwater and calm wind in the adjacent territories were identified. A model of the wind shadow zone has been compiled, which allows the designer to zone the territory adjacent to the building at the design stage, taking into account the aeration regime of the development.

Numerical Simulation of Meteorological Conditions and Air Quality above Tomsk, West Siberia

This paper presents the simulation results of meteorological and air quality parameters for the Siberian city of Tomsk predicted by mesoscale meteorological and chemical transport models. Changes in the numerically predicted wind velocity fields, temperature, and concentration of major air pollutants were modelled in detail for the selected dates, when anticyclonic weather with cloud free and calm wind conditions was observed in Tomsk. The simulation results have shown that stable or neutral atmospheric stratification with light wind and low ambient air temperature (−30, −20 °C) are the most unfavorable meteorological conditions leading to the near surface pollutants accumulation. The numerical calculation results were compared with observation data from the Joint Use Center (JUC) “Atmosphere” of V.E. Zuev Institute of Atmospheric Optics (IAO) and showed good agreement.

Validating CFD Predictions of Flow over an Escarpment Using Ground-Based and Airborne Measurement Devices

Micrometeorological observations from a tower, an eddy-covariance (EC) station and an unmanned aircraft system (UAS) at the WINSENT test-site are used to validate a computational fluid dynamics (CFD) model, driven by a mesoscale model. The observation site is characterised by a forested escarpment in a complex terrain. A two-day measurement campaign with a flow almost perpendicular to the escarpment is analysed. The first day is dominated by high wind speeds, while, on the second one, calm wind conditions are present. Despite some minor differences, the flow structure, analysed in terms of horizontal wind speeds, wind direction and inclination angles shows similarities for both days. A real-time strategy is used for the CFD validation with the UAS measurement, where the model follows spatially and temporally the aircraft. This strategy has proved to be successful. Stability indices such as the potential temperature and the bulk Richardson number are calculated to diagnose atmospheric boundary layer (ABL) characteristics up to the highest flight level. The calculated bulk Richardson values indicate a dynamically unstable region behind the escarpment and near the ground for both days. At higher altitudes, the ABL is returning to a near neutral state. The same characteristics are found in the model but only for the first day. The second day, where shear instabilities are more dominant, is not well simulated. UAS proves its great value for sensing the flow over complex terrains at high altitudes and we demonstrate the usefulness of UAS for validating and improving models.

MAPPING URBAN VENTILATION CORRIDORS AND ASSESSING THEIR IMPACT UPON THE COOLING EFFECT OF GREENING SOLUTIONS

Over the past decades, climate change has become among the top issues challenging cities worldwide, endangering the urban infrastructures and threatening the health of millions of people. Hence, climate action, both in terms of mitigation and adaptation to climate change, has become a priority for urban planning. This work introduces an example of the promising role that spatial analysis and statistical modelling, employing Geographical Information Systems (GIS) and freely available satellite and land-based data, can provide in supporting urban climate design and policymaking. In particular, this study puts special attention on the Urban Heat Island (UHI) phenomenon. Here, we first introduce a simple, but effective morphological-based approach for mapping potential ventilation corridors across cities of uniform built-up structure, as a common UHI mitigation measure. Then, we propose a methodology for assessing the relative role of these corridors in maximizing the impacts of green solutions upon lowering high temperature. Results show that even under very calm wind conditions, there is still an opportunity for maximizing the benefits of greening measures on the urban climate. Also, it has been demonstrated that green ventilation corridors are more effective during night-time when the UHI effect is peaked. The research findings are very promising, especially for cities where wind is a marginal potentiality.

Effect of Breaking Waves on Near-Surface Mixing in an Ocean-Wave Coupling System under Calm Wind Conditions

Estimating wave effects on vertical mixing is a necessary step toward improving the accuracy and reliability of upper-ocean forecasts. In this study, we evaluate the wave effects on upper-ocean mixing in the northern East China Sea in summer by analyzing the results of comparative experiments: a stand-alone ocean model as a control run and two ocean–wave coupled models that include the effect of the breaking waves (BW) and of the wave–current interaction (WCI) with a vortex-force formalism. The comparison exhibits that under weak wind conditions, the BW effect prescribed by wave dissipation energy significantly enhances near-surface mixing because of increased downward turbulent kinetic energy (TKE), whereas the WCI has little effect on vertical mixing. Increased TKE results in a mixed-layer depth deepened by ~46% relative to the control run, which provides better agreement with the observed surface thermal structure. An additional experiment with local wind–based BW parameterization confirms the importance of nonlocally generated waves that propagated into the study area upon near-surface mixing. This suggests that under calm wind conditions, waves propagated over distances can largely affect surface vertical mixing; thus, ocean–wave coupling is capable of improving the surface thermal structure.

Longitudinal wind speed time series generation to wind turbine controllers tuning

Although there are a wide variety of applications that require wind speed time series (WSTS), this paper emphases on WSTS to be used into wind turbine controllers tuning. These simulations involve several WSTS to perform a proper assessment. These WSTS must assure realistic wind speed variations such as wind gusts and include some rare events such as extreme wind situations. The architecture proposed to generate this WSTS is based on autoregressive models with certain post-processing. The methodology used is entirely described by precise notation as well as it is parametrized by means of data gathered from a weather station. Two main different simulations are performed and assessment; the first simulation is fed by weather data with high wind speed and great variability. The second simulation, on the opposite, use calm wind speed as a data source.Article History: Received 1st June 2018; Received in revised form Sept 6th 2018; Accepted October 10th 2018; Available onlineHow to Cite This Article: González, A.G. and Guede, J.M.L. (2018) Longitudinal Wind Speed Time Series Generated With Autoregressive Methods For Wind Turbine Control. International Journal of Renewable Energy Development, 7(3), 199-204.https://doi.org/10.14710/ijred.7.3.199-204