the authors discuss the design and construction , types and usage limitations of wind tunnels. Topics include the use of wind tunnels to analyze wind loading on scaffold structures the characteristics of the Architecture and Building Research Institute wind tunnel project; analysis of the wind environment and air quality in densely populated areas using wind tunnel experiments; wind tunnel investigation into the drag characteristics of
catamaran form; and environmental wind tunnels designed and constructed to investigate a wide range of aerodynamic tasks.
Chapter 1 - In 2001, the ABRI (Architecture and Building Research Institute, Ministry of the Interior, Taiwan) initiated a project to establish an environmental wind tunnel in the Kui-Ren campus of National Cheng Kung University. This project was completed in 2004. The wind tunnel is of a closed-return type, featuring two test sections in series. The primary test section is 3 m by 2.6 m in cross section and 36.5 m in length; the secondary test section is 6 m by 2.6 m in cross section and 21 m in length. The wind tunnel uses a 500 KW axial fan. Immediately after the completion of the wind tunnel, the wind tunnel was calibrated.

The results of the calibration indicate that the maximum speed at the inlet of the primary test section is 36 m/s and that the turbulence intensity and non-uniformity of the flow measured at the inlet of the main test section are less than 0.3% and 0.4%, respectively. At a flow of speed more than 30 m/s, the energy ratio calculated from the fan test data, is about 0.94, which almost coincides with that predicted by the design data. The flow quality of the wind tunnel was further examined using an experiment with two circular cylinders at Reynolds numbers in the critical regime. The base pressure coefficients measured were found to be in good agreement with those reported in the literature.
The oil-film flow visualization performed in this experiment further provides information regarding the flow patterns corresponding to different flow states in the critical regime.
Chapter 2 - This chapter presents an experimental investigation of wind flow characteristics and air quality along a street canyon located within a dense urban area. Four typical models of a highly populated urban area are studied and wind tunnel experiments are carried out over an extended range of the applied wind directions. The building patterns are represented by 1:100 scale models, where wind velocity, wind pressure and tracer gas concentrations are measured along the two sides of the street.
A serious problem associated with wind tunnel tests on the flow around buildings is that of blockage. To overcome such problem, an experiment for determining the building blocking effect was carried out and a correction factor was estimated and considered in the measured pressures. Details of such experiment are given at the end of this chapter.

The study results provide evidence that building configurations and wind directions are very important factors in determining both wind flow and pollutant dispersion characteristics within urban domains. Also, the results demonstrate that gaps between buildings are a very important factor to be considered by urban planners and designers, because, for a given building height, larger gaps induce more wind in urban canyons, thus improving the ventilation process.

Chapter 3 - The breakdown into the resistance or drag components of catamarans has been widely discussed worldwide in the last 30 years. The resistance interference (both wave and viscous parts) has been the major part among the components. Wave resistance interference can be rather easily estimated using tank test, whilst the viscous component is rather complicated to determine. Tank test can be used to estimate the skin friction, but correction should be made attributed to interference of wave resistance on skin friction or viscous resistance. In order to isolate the viscous resistance, hence free from wave component, wind tunnel test was carried out. A series of tests of catamaran forms were carried out using low speed wind tunnel.
Various configurations of slender catamaran were made in order to identify the viscous resistance (hence the form factor) and viscous resistance interference.
The Chapter discusses the construction and experimental procedure of the wind tunnel test. Verifications were made with tank test and CFD (computational fluid dynamics) data in order to examine the accuracy of using wind tunnel. Overall results demonstrate the effectiveness of using wind tunnel test to estimate viscous resistance and its interference component.

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