Search

Two kinds of measurement errors have been observed in the recently developed UAT-2 ultrasonic anemometer. One is the flow distortion produced by a “blocking effect”, and the other is the angle of attack caused by the vertical misalignment of the instrument. Here, we study these errors and discuss the possible correction methods. Via a wind tunnel experiment and numerical simulation, a 3D calibration matrix was developed to correct the “blocking effect”. In the field test, the angle of attack was detected by an inclinometer settled on the reference plane of the anemometer, and the instrumental misalignment or tilt was corrected by a coordinate transformation. The combined use of an inclinometer and the proposed correction method may help find a new approach for vertical velocity correction.

In this paper, the authors use ultrasonic data over a homogeneous surface to calculate the Kolmogorov constants of velocity, temperature, CO2, and water vapor. The authors find that the constants are all within the range determined by former experiments and that they are universally independent of the stability.

The Regional Atmospheric Modeling System (RAMS) and the computational fluid dynamics (CFD) codes known as FLUENT are combinatorially applied in a multi-scale numerical simulation of the urban surface layer (USL). RAMS and FLUENT are combined as a multi-scale numerical modeling system, in which the RAMS simulated data are delivered to the computational model for FLUENT simulation in an offline way. Numerical simulations are performed to present and preliminarily validate the capability of the multi-scale modeling system, and the results show that the modeling system can reasonably provide information on the meteorological elements in an urban area from the urban scale to the city-block scale, especially the details of the turbulent flows within the USL.

The questions on how vortices are constructed and on the relationship between the flow patterns and concentration distributions in real street canyons are the most pressing questions in pollution control studies. In this paper, the very large eddy simulation (VLES) and large eddy simulation (LES) are applied to calculate the flow and pollutant concentration fields in an urban street canyon and a cross-road respectively. It is found that the flow separations are not only related to the canyon aspect ratios, but also with the flow velocities and wall temperatures. And the turbulent dispersions are so strongly affected by the flow fields that the pollutant concentration distributions can be distinguished from the different aspect ratios, flow velocities and wall temperatures.

In this paper, the pedestrian level wind safety problem induced by high-rise buildings has been studied using the computational fluid dynamics (CFD) codes Fluent. The verification by use of wind tunnel data shows that Fluent can fairly reproduce the flow field in the areas adjacent to the structure when a realizable k-e turbulence model is adopted in calculations. The results of the numerical simulations including seven cases show that the existence of high-rise buildings does increase the wind hazard probability at the pedestrian level; furthermore, the wind direction, the geometric size of structures and the layout of structures can obviously affect the pedestrian level wind environment. However, trees on the pavement do not contribute much in reducing the wind hazard probability.