A.T. Soilemes

On the combination of air velocity and flow measurements in single sided natural ventilation configurations

Abstract Single sided natural ventilation configurations are very frequent especially in buildings in urban environments. Four single sided ventilation experiments were carried out in a full scale outdoor Test Cell facility. Air velocity measurements were taken at various heights in the middle of the opening. The average air flow rate through the opening was derived using the tracer gas decay technique. This work presents the results of an investigation into the relationship between the air velocity at the opening and the bulk air flow rate measurements. The paper presents a description of the experimental set-up as well as a qualitative discussion of the results.

Predicting single sided natural ventilation rates in buildings

Natural ventilation contributes significantly in reducing the cooling load of buildings and in increasing thermal comfort. Single sided natural ventilation configurations are very frequent especially in urban environments. Fifty-two single sided natural ventilation configurations have been studied experimentally and are compared with the predictions of six different network ventilation models. The heat and mass transfer characteristics of the studied cases are analysed and discussed. Finally, a new model to predict air flow rates in single sided natural ventilation configurations is proposed.

An experimental study of the near-wake structure of a wind turbine operating over complex terrain

Abstract Wind parks are often cited in complex terrain whose features determine the wind flow over the area. Results from a field experiment, comprising in-situ and remote sensing techniques (high-resolution acoustic sounders), concerning the upwind area and the near-wake region behind a single medium-sized wind turbine are presented. The experimental site is the Samos Island Wind Park installed on top of a 390 m-high saddle. Because of the topography, wind speed acceleration and channeling effects are expected; thus, the commonly used logarithmic profile is not valid, and the choice of a representative surface roughness length z o is difficult. Interesting features of the profiles of the standard deviation of the ambient wind speed are also presented. The obtained results reveal a nonlinear interaction of the near wake with the turbine-tower shadowing, while cross-wind wake profiles indicate a potential core structure. The effect of ambient turbulence is apparent, especially at lower wind speeds, even at a distance of one rotor diameter (1 D ) behind the turbine. The wake centerline at distances greater than 1 D is often observed at heights greater than the hub-height and attributed to the wind flow characteristics over the Wind Park. Finally, evidence of rotational motion inside the wake is identified.

Influence of background flow on evolution of saronic gulf sea breeze

Abstract Results from an experimental campaign at the coastline of the Saronic Gulf during the summer of 1992 are presented. The frontal intensity and the rotation of the wind hodograph at the shoreline during sea-breeze case:; are examined under different background flow conditions. The frontal intensity classification is based on the vertical velocities induced, as measured by a high resolution acoustic sounder. Three representative cases are presented. Conclusions are based on the analysis of all observed sea-breeze flows. Background off-shore or shore-parallel flows are more probable to create a strong or weak front, respectively. The development of frontal characteristics under background on-shore flow is attributed to off shore land features. The wind hodograph rotation is shown to be associated to the initial direction of the sea breeze, which is determined by the background flow direction. When the background flow possesses a westerly component the hodograph shows anticlockwise rotation, while an easterly background component causes the wind vector rotation to be clockwise.

Boundary layer evolution over a large and broad mountain basin

SummaryIn this study observations of the vertical structure of the Atmospheric Boundary Layer (ABL), recorded at a broad mountainous valley are presented. The vertical profiles of temperature, wind speed and direction up to a height of about 800 meters over the valley bottom have been measured and the temporal evolution of ABL structure of the area has been studied. Specifically, the mechanism of nocturnal inversion destruction during morning hours has been studied, which is of major importance in the study of the dispersion of air pollutants over the area. These observations suggest that the break up of nocturnal inversion during morning hours is mainly caused by a combined mechanism, the build up of the Convective Boundary Layer (CBL) and the presence of upslope winds, resulting to a continuous descent of the top of the nocturnal inversion.

A layer detection and classification algorithm for sodar facsimile records

Abstract This paper describes an application of image processing and pattern recognition techniques for the detection and classification of the layer echo structure within a window of a facsimile record of a monostatic acoustic sounder (sodar). The algorithm identifies automatically the upper and lower boundary of every layer in a facsimile record, even if it is a complex pattern. Consequently, it uses the boundaries of the layers to extract the classification features. This technique provides quantitative information for a facsimile record and follows a different approach than previous classification schemes that classify the record manually according to predetermined patterns. The algorithm was developed and tested using data collected by two different types of sodar under various meteorological conditions. An overall skill better than 90 per cent of the cases was achieved. The algorithm experienced some difficulty identifying the thermal structure over transitional atmospheric conditions, during which ...

A hot-wire based, research atmospheric turbulence probe : design analysis and performance

The design details, constructional characteristics and performance of a research atmospheric turbulence probe based on the hot wire technique are presented. The presentation emphasizes issues related to the hot-wire calibration procedure and the effect of the data processing on the system reliability. The probe is capable of measuring the three wind components, the mean and fluctuating temperature.