Local Wind Conditions Research Articles

NEW CALIBRATION METHOD APPLICABLE TO SIGNIFICANT WAVE HEIGHTS OBTAINED BY X-BAND RADAR

This paper presents a new calibration method of wave heights obtained using marine X-band radar wave measurement system. Realtime information about sea state, such as wave height, period, and direction, is crucial for coastal protection as well as offshore operational management. In the last 30 years, routine sea state measurements have been carried out using different measuring devices such as mooring buoys, pressure gages, and acoustic type gages. Although such devices provide reliable measurements, they are subject to frequent damages and losses. Therefore, considerable interest has been shown lately in the use of remote sensing techniques to measure waves and surface currents. In recent years, it has been demonstrated that radar images of the ocean surface provide reliable information about the spatial behavior of wave fields. Many systems which utilize a commercial marine X-band radar for providing time series of radar backscatter images from the sea surface have been developed. (Borge et al., 2004, Plant and Zunk, 1997 ) Wave measurement system using marine X-band radar has many advantages over conventional wave gages, which are more robust in severe sea state, easy to maintain, economic maintenance cost, etc. However, one critical shortcoming of X-band radar system using in operational wave measurements is inaccuracy in the estimation of wave heights during weak local wind conditions. This is a critical weakness when people try to use measured wave data in the statistical estimation of design waves. It is not an easy task to overcome this critical shortcoming. It is because this problem resides in the X-band radar system’s inherent sea surface scanning mechanism, which is called Bragg Resonance mechanism. It is known that under various conditions signatures of the sea surface are visible in the near ranges (usually less than 5.4 km) of marine radar images. These signatures are known as sea clutter because they are undesirable for navigational purposes and generally suppressed by filter algorithm. Sea clutter is mainly due to the backscatter through Bragg resonance with ocean waves of wavelengths similar to those of the transmitted electromagnetic waves. The longer waves become visible in the radar images because they modulate the sea clutter signals. For the case of X-band radar (frequency of 9.4 GHz), sea surface with ripple waves (wavelength of about 2 cm) provide Bragg resonance, henceforth results in accurate estimation of wave heights. On the other hand, swell waves without ripples when no local wind available, are tend to be significantly underestimated.

Outdoor ventilation performance of various configurations of a layout of two adjacent buildings under isothermal conditions

This paper explores the pedestrian-level wind environment around two buildings of unequal heights for the effects of ratio of height of upwind building to that of downwind building, referred to as buildings height ratio, spacing distance between the buildings, and direction of ambient wind, on the outdoor air ventilation. The objective is to propose appropriate spacing distances for various configurations of this type of buildings layout in a suburban area of Kuala Lumpur, which would enable harnessing the full ventilation potential of the local wind conditions. A three-dimensional numerical technique employing computational fluid dynamics simulation of continuity and Reynolds-Averaged Navier-Stokes equations was used to study the turbulent flow field around the full-scale sizes of the buildings. Results indicate the influence of spacing distance between buildings, relative heights of the buildings and direction of ambient wind on outdoor ventilation. Results also show that 3-D turbulent flow processes such as lateral and secondary flows play significant roles in defining the wind flow pattern and ventilation availability. The perpendicular wind direction presents remarkable adverse effects compared to the inclined direction, while a higher upwind building height which would ordinarily be expected to proportionally obstruct wind flow could be of advantage, at low values of building height ratios, in enhancing outdoor ventilation. The findings established the need to give consideration to climatic factors such as wind flow and direction in planning urban cities, as it affects buildings to be situated in close proximity, especially when there is height difference.

Strategy in Front of Complex Infected Cranial Defects Overlying Dura Mater. Feasibility and Safety of Negative Pressure Wound Therapy

Although rare, large cranial infected defects are challenging for practitioners, especially when the dura mater is involved. These complex full-thickness wounds (scalp, bone, and dura mater) commonly occur after surgery, trauma or failed reconstructive procedures. Many patients are poor candidates for immediate reconstruction because of original pathology, patient's general state, previous radiotherapy, which compromises the locally available tissue, depth of the sepsis. For these challenging patients, a two-step procedure (cleanliness then reconstruction) has to be proposed. Recently, few authors report the use of negative pressure wound therapy, NPWT, in association with a first-step cleanliness surgery with encouraging results. Methods: We report three consecutive cases with standardized two-step procedure for complex full-thickness cranial wounds. First step is a cleanliness surgery associated with NPWT using a continue negative pressure ranging from 25 to 75 mm Hg. Safety of NPWT protocol is evaluated by neuropsychological and clinical examination. A second step for reconstruction is then performed. Results: Good outcomes were achieved in all cases without any complication due to NPWT with a 9-month follow-up. No significant difference was found between neuropsychological examination with or without NPWT. Conclusion: NPWT is a safe procedure optimizing local wound conditions for poor candidates for immediate reconstruction in complex infected cranial defects overlying the dura mater.

The effect of wind on the optimal design and performance of a modular air-cooled condenser for a concentrated solar power plant

Air-cooled condensers overcome one of the main issues facing the construction of concentrated solar power plants by replacing water with air as the medium for cooling of the steam turbine waste heat. The recent development of modular air-cooled condensers as an improvement on conventional designs means that the effect of wind on their performance needs to be quantified. This study examines these effects by numerically modelling the condenser at the system level and using the results to build a mathematical model to predict the optimal condenser configuration. These types of mathematical models can be easily used by a power plant designer to quickly predict what the performance of the power plant will be based on the condenser geometry using data from numerical models of appropriate size and boundary conditions. The designer can then make a trade-off between the plant performance and initial capital costs in commissioning the power plant.It has been found that when trying to optimise the performance, the historical wind condition distributions for a specific location should be used as significantly different condenser designs and orientations are required at different locations due to these distributions of local wind conditions.

Controls on monthly estuarine residuals: Eulerian circulation and elevation

The Dee Estuary, at the NW English–Welsh border, is a major asset, supporting: one of the largest wildlife habitats in Europe, industrial importance along the Welsh coastline and residential and recreational usage along the English coast. Understanding of the residual elevation is important to determine the total water levels that inundate intertidal banks, especially during storms. Whereas, improved knowledge of the 3D residual circulation is important in determining particle transport pathways to manage water quality and morphological change. Using mooring data obtained in February–March 2008, a 3D modelling system has been previously validated against in situ salinity, velocity, elevation and wave observations, to investigate the barotropic–baroclinic wave interaction within this estuary under full realistic forcing. The system consists of a coupled circulation-wave-turbulence model (POLCOMS-WAM-GOTM). Using this modelling system the contribution of different processes and their interactions to the monthly residuals in both elevation and circulation is now assessed. By studying a tidally dominated estuary under wave influence, it is found that baroclinicity induced by a weak river flow has greater importance in generating a residual circulation than the waves, even at the estuary mouth. Although the monthly residual circulation is dominated by tidal and baroclinic processes, the residual estuarine surface elevation is primarily influenced by the seasonal external forcing to the region, with secondary influence from the local wind conditions. During storm conditions, 3D radiation stress becomes important for both elevation and circulation at the event scale but is found here to have little impact over monthly time scales.

Active current sheets and candidate hot flow anomalies upstream of Mercury's bow shock

Hot flow anomalies (HFAs) represent a subset of solar wind discontinuities interacting with collisionless bow shocks. They are typically formed when the normal component of the motional (convective) electric field points toward the embedded current sheet on at least one of its sides. The core region of an HFA contains hot and highly deflected ion flows and rather low and turbulent magnetic field. In this paper, we report observations of possible HFA‐like events at Mercury identified over a course of two planetary years. Using data from the orbital phase of the MESSENGER mission, we identify a representative ensemble of active current sheets magnetically connected to Mercury's bow shock. We show that some of these events exhibit magnetic and particle signatures of HFAs similar to those observed at other planets, and present their key physical characteristics. Our analysis suggests that Mercury's bow shock does not only mediate the flow of supersonic solar wind plasma but also provides conditions for local particle acceleration and heating as predicted by previous numerical simulations. Together with earlier observations of HFA activity at Earth, Venus, Mars, and Saturn, our results confirm that hot flow anomalies could be a common property of planetary bow shocks and show that the characteristic size of these events is controlled by the bow shock standoff distance and/or local solar wind conditions.

Replacing mechanical thermometers with electronic thermometers in a Mediterranean test station and its impact on climatology

In the last two decades of the 20 th century, most meteorological networks replaced traditional mechanical thermometers (usually placed inside a Stevenson screen) with electronic ones (usually in the open air, protected by a plastic shelter). Impacts of such instrumental change on the climatology of daily minimum and daily maximum temperatures are assessed here, by analysing eleven years of data from a couple of stations operating in parallel in the same test site in a location with a Mediterranean climate. Seasonal effects (i.e. monthly biases ranging from -0.8C to +1C) were detected on maximum temperatures, but they compensate each other in the yearly average. In minimum temperatures, electronic thermometers introduced a -0.75C bias, regardless of the season. Specific biases due to horizontal winds and to vertical heat fluxes were also detected and studied. Two possible causes of the climatological bias were investigated: local wind conditions and different responses to turbulent heat fluctuations by electronic and mechanical thermometers. Other possible causes exist, but they could not be investigated due to a lack of data. The present study shows that, in the test site, replacing traditional thermometers with modern ones in climatological networks introduced an underestimate in minimum temperatures. This suggests that in locations with similar microclimates the real atmospheric warming could be even greater than that observed to date.

Coordinated contribution of wind turbines to frequency regulation by model predictive control

This work proposes an innovative control technique for improving the contribution to the grid frequency regulation provided by a set of wind power generators belonging to a wind farm. Models of individual generators and of the conventional grid primary frequency control are developed and used for designing a model predictive controller. A proper estimation algorithm is also introduced in order to provide both the dynamical state of the wind turbines and the actual local wind conditions to the regulator. The availability of this data makes the control algorithm able to improve the participation of the whole wind farm to the frequency regulation by suitably coordinating and differentiating the contribution of the individual generators. The proposed strategy is tested on a large wind farm using a dedicated real-time/real-data simulation environment.

Techno-economic assessment of the application of small-scale wind turbines

In the present work, a tool is proposed for the evaluation of micro-wind turbine performances in the Australian cities. The power curves provided by the manufacturers were combined with the two-parameter Weibull function representative of the local wind conditions. Calculations demonstrate that when taking into account the only wind speed magnitude, the horizontal axis micro-wind turbines have greater capacity factors than the vertical axis micro-wind turbines for similar wind conditions. Turbine capacities were then mapped over a wide range of wind conditions assuming the wind distribution characterised by Weibull parameters. By considering the market price of electricity, the income of a power source can be evaluated. The critical wind-condition boundary needed to provide a beneficial active micro-wind turbine was determined for one horizontal axis micro-wind turbine using a hypothetical income map.

A review and recent developments in the optimal wind-turbine micro-siting problem

Abstract This paper presents a review of the current state of the art solutions to the problem of wind farm optimal design. The aim of this work is to present the problem by identifying the most relevant issues involved in the design of a wind farm, as well as to discuss the optimization techniques and wind farm models used in the published literature. An appropriate wind turbine layout is vital in order to obtain adequate performance in relation to the exploitation and operation of the plant during its lifespan. There are several factors that influence wind farm design, chief among them are the calculation of the overall energy yield by the wind farm and the initial investment. The energy produced depends on the local wind conditions and the interference caused by wind turbines nearby. The investment is mainly related to wind turbine acquisition, civil works and electrical infrastructure. However, these are not the only items that influence the design of a wind farm since economic indicators, environmental issues, local regulations, or the presence of wind farms should also be taken into account when deciding the design of the wind farm. Even in the case of the most simplified objective function (maximizing the annual energy produced) the optimization problem cannot be solved by classical optimization techniques. To cope with this problem, most authors have used meta-heuristics techniques which have proved to be efficient when searching for the optimal solution to this problem. The purpose of this paper is to review previous work by offering a clear outline of the latest advances, as well as to highlight the main aspects which need to be taken into account when tackling the wind farm design problem. In addition, in a conclusion of the review, future needs have been identified.

Exoplanet transit variability: bow shocks and winds around HD 189733b

By analogy with the solar system, it is believed that stellar winds will form bow shocks around exoplanets. For hot Jupiters the bow shock will not form directly between the planet and the star, causing an asymmetric distribution of mass around the exoplanet and hence an asymmetric transit. As the planet orbits thorough varying wind conditions, the strength and geometry of its bow shock will change, thus producing transits of varying shape. We model this process using magnetic maps of HD 189733 taken one year apart, coupled with a 3D stellar wind model, to determine the local stellar wind conditions throughout the orbital path of the planet. We predict the time-varying geometry and density of the bow shock that forms around the magnetosphere of the planet and simulate transit light curves. Depending on the nature of the stellar magnetic field, and hence its wind, we find that both the transit duration and ingress time can vary when compared to optical light curves. We conclude that consecutive near-UV transit light curves may vary significantly and can therefore provide an insight into the structure and evolution of the stellar wind.

Estimating population exposure to high ozone concentrations under major meteorological conditions in a coastal city

Background: Recent climate change and urbanization enhance the interest in ozone (O3) exposure in vulnerable population. Further advances in exposure assessment technology will be needed for quantifying population exposure to high O3 levels in complex coastal urban area. Aims: In this study, the population exposure to high O3 concentrations was estimated under the major meteorological conditions in a coastal city. Methods: We estimated the population exposure in Busan metropolitan city in Korea by matching O3 concentrations predicted by meteorological-air quality models (WRF-CMAQ) with geographically distributed population. The population data for 2000 were obtained from the Statistics Korea classified by age, gender, and the smallest administrative unit. The distributions of the estimated population exposure to high O3 concentration were compared between the different wind conditions on the high O3 days. Results: The estimated population exposure to high O3 concentrations was largely influenced by the wind condition in the study area. Especially, the condition of inland penetration of sea breeze determined significantly the distributions of the exposure in the city. Conclusions: The results of this study suggest that the estimation of population exposure to high O3 concentrations having high sensitivity on short-term exposure will be needed for considering the characterized local wind conditions in the complex coastal city to improve the uncertainty of the estimation.

Terapia por pressão negativa na ferida traumática complexa do períneo

To review the experience (2011 and 2012) of Wound Center of Plastic Surgery Service, Clinics Hospital, Faculty of Medicine, University of São Paulo, with treatment of complex traumatic wounds in the perineal region with the association of negative pressure wound therapy followed by a surgical skin coverage procedure. This was retrospective analysis of ten patients with complex wound in the perineum resulting from trauma assisted by the Department of Plastic Surgery in HC-USP. Negative pressure was used as an alternative for improving local conditions, seeking definitive treatment with skin grafts or flaps. Negative pressure was used to prepare the wound bed. In patients, the mean time of use of negative pressure system was 25.9 days, with dressing changes every 4.6 days. After negative pressure therapy, 11 local flaps were performed in nine patients, with fasciocutaneous anterolateral thigh flap used in four of these. Mean hospital stay was 58.2 days and accompaniment in Plastic Surgery was 40.5 days. The use of negative pressure therapy led to improvement of local wound conditions faster than traditional dressings, without significant complications, proving to be the current best alternative as an adjunct for the treatment of this type of injury, always followed by surgical reconstruction with grafts and flaps.

Dynamic modelling of sea-surface roughness for large-eddy simulation of wind over ocean wavefield

AbstractWind blowing over the ocean surface can be treated as a turbulent boundary layer over a multiscale rough surface with moving roughness elements, the waves. Large-eddy simulation (LES) of such flows is challenging because LES resolves wind–wave interactions only down to the grid scale,$\Delta $, while the effects of subgrid-scale (SGS) waves on the wind need to be modelled. Usually, a surface-layer model based on the law of the wall is used; but the surface roughness has been known to depend on the local wind and wave conditions and is difficult to parameterize. In this study, a dynamic model for the SGS sea-surface roughness is developed, with the roughness corresponding to the SGS waves expressed as${\alpha }_{w} \hspace{0.167em} { \sigma }_{\eta }^{\Delta } $. Here,${ \sigma }_{\eta }^{\Delta } $is the effective amplitude of the SGS waves, modelled as a weighted integral of the SGS wave spectrum based on the geometric and kinematic properties of the waves for which five candidate expressions are examined. Moreover,${\alpha }_{w} $is an unknown dimensionless model coefficient determined dynamically based on the first-principles constraint that the total surface drag force or average surface stress must be independent of the LES filter scale$\Delta $. The feasibility and consistency of the dynamic sea-surface roughness models are assessed bya prioritests using data from high-resolution LES with near-surface resolution, appropriately filtered. Also, these data are used fora posterioritests of the dynamic sea-surface roughness models in LES with near-surface modelling. It is found that the dynamic modelling approach can successfully capture the effects of SGS waves on the wind turbulence withoutad hocprescription of the model parameter${\alpha }_{w} $. Also, for${ \sigma }_{\eta }^{\Delta } $, a model based on the kinematics of wind–wave relative motion achieves the best performance among the five candidate models.

Pleural mesothelioma in relation to meteorological conditions and residential distance from an industrial source of asbestos

ObjectivesFew studies have focused on pleural mesothelioma and environmental exposure in individuals residing around an industrial source of asbestos. The aim of this study is to determine whether residential distance...

Modelling the spatial concentrations of bird migration to assess conflicts with wind turbines

Bird migration and wind energy production exploit a similar airspace. There is a well-founded claim that conservation should aim at facilitating both activities. Negative effects can be mitigated either by avoiding a spatial concurrence or by accounting for the temporal course of migration and stopping wind turbines during peak flight activities. In this study we promote a new methodological approach to reduce potential conflicts in the planning as well as during the operation phase of a wind energy project. The basis is a new spatially explicit model for broad front migration. It allows to quantify the collision risk with respect to topography. We simulated migration of non-soaring birds across Switzerland. Model parameters were tuned to achieve results in accordance with current expert knowledge based on many years of visual observations and radar measurements. The resulting maps were used to define areas with different collision risks. For medium and high risk areas, we propose a permanent monitoring system, which is able to shut down the local turbines during peak migration. We evaluated the impact of such a shutdown regime in five specific sites with quantitative radar data for at least one migration season. The model presented here is a simple preliminary, but robust, approach. The main weakness of the model is the use of large-scale rather than local wind conditions. Within the Alps, local wind fields can differ considerably from the general pattern, and accordingly also the distribution of flight directions. We hope to provide a basis for similar models in other geographic areas. In addition, we call for the use of large scale monitoring data, as hopefully will soon be available from weather radar networks, to validate any kind of spatially explicit migration models.

Study of the meteorological tide in the Río de la Plata

The meteorological tide generation and the characteristics of its propagation into the Río de la Plata are examined in this paper. Meteorological tide refers to departures of the sea surface elevation from the predicted astronomical tide during days to a few weeks and is generated by atmospheric forcings. The study was carried out analyzing hydrographic records and also using a hydrodynamic numerical model. The numerical model was implemented both in a regional domain and in a local domain focused in the Río de la Plata. The numerical model allowed us to understand the generation of the events and the relative importance of the remote and local forcings. Based on hydrographic records of the Río de la Plata and NCEP–NCAR reanalysis data, the synoptic conditions leading to the most significant meteorological tide events were identified. Using simultaneous hydrographic records at various stations in the Río de la Plata, we analyzed the propagation time of the events between stations and the amplitudes changes. The results show that the main meteorological tide events are generated in the Argentinean continental shelf and then propagate northward as coastal trapped waves until they reach the estuary. For the largest events in the studied data series a good relationship between the amplification in their amplitudes and the local wind conditions was found.

Investigation of Wake Effects on the Energy Production of Small Wind Turbines

This paper examines the impact of natural and man-made obstructions on local wind conditions and the performance of small wind turbines when impacted by wake effects. The rural site used for this research contains three Skystream 3.7 turbines in close proximity to each other and several buildings. A 13 m meteorological tower with wind speed and direction sensors was installed in a nearby open area. An empirical analysis was conducted to provide a comparison of turbine performance and measured wind speed for each turbine as a function of localized disturbances caused by turbine placement. Turbine proximity to nearby buildings was observed to cause an overall reduction in power production, although cases of apparent wind speed-up induced by the buildings, and increased relative power output, were also observed. A reduction in wind turbine power output due to the wake of an adjacent turbine was observed. Overall, the turbine closest to the buildings produced about 10% less energy during the measurement period than the most distant turbine. This study confirmed the importance of careful micrositing of small wind turbines, and the complexity of the flow field near buildings and wind turbines.

Dynamical partitioning of directional ocean wave spectra

Directional wave spectra generally exhibit several peaks due to the coexistence of wind sea generated by local wind conditions and swells originating from distant weather systems. This paper proposes a new algorithm for partitioning such spectra and retrieving the various systems which compose a complex sea-state. It is based on a sequential Monte-Carlo algorithm which allows to follow the time evolution of the various systems. The proposed methodology is validated on both synthetic and real spectra and the results are compared with a method commonly used in the literature.

A Preliminary Approach of the Technical Feasibility of Offshore Wind Projects along the Brazilian Coast

This work seeks to demonstrate the technical feasibility of offshore wind projects by calculating the preliminary estimate of wind energy production in the Brazilian marine environment, through a simplified methodology based on currently available data in a case study performed with the application of wind turbines. The Exclusive Economic Zone of Brazil is about 3.6 million km², an area that can be harnessed for offshore wind energy production. The case study was conducted in Itamaracá Island, Pernambuco state with the aim of supplying the local energy demands. An analysis was carried out on the local wind conditions through an ocean wind map measured at a height of 10 m, and therefore, the wind speed was extrapolated to 90 m using the logarithmic law. The Weibull frequency distribution and the annual energy production were calculated. The results presented showed that three wind turbines at a rated power of 3 MW, including a calculated annual average wind speed of 7.15 m/s would generate around 30,000 MWh/year, which would be sufficient to ensure energy throughout the year in Itamaracá Island.