**3. The evaluation of pedestrian level wind condition and comfort criteria**

In the evaluation of wind comfort, besides the wind velocity, the frequency of occurrence is also important. For this reason, the wind comfort criteria include the threshold wind speed and frequency of occurrence that will cause discomfort to pedestrians. A wide variety of wind comfort criteria based on the threshold mean wind speed and probability of exceeding have been previously proposed [43–46]. The following criteria are required for the evaluation of the wind climate environment favorable for pedestrians at the comfort level: (1) Statistical meteorological data of the meteorological station closest to the study area; (2) Topographic and aerodynamic information of the study area and (3) Mechanical wind comfort criteria. Aerodynamic data helps to calculate and interpret statistical data in a particular region obtained from the weather station. The converted data at the building location is then compared with the wind comfort criteria. The meteorological data received from the meteorological station consists of the hourly average wind speed. (Ums: measured at 10 m altitude) wind and wind direction at terrain (y0, meteo = 0.03 m). These wind speed data from the weather station are substituted into the equation below to calculate the probability of exceeding the threshold wind speed [43, 47, 48].

$$P(>U) = \exp\left[-\left(\frac{U}{c}\right)^k\right] \tag{1}$$

Where P (>U) represents the probability of exceeding the wind speed; U is the average wind speed magnitude of the area where the building is located, the terrain; C is the dispersion parameter and k is the building form parameter. These constants are obtained by applying Eq. (1) to the meteorological data. Then the statistical information must be converted to the area of interest by means of aerodynamic information using the amplification factor R (Eq. (2)) This amplification factor consists of the design related contribution and the terrain related contribution (Eq. (3)) [47]. The design contribution includes modification of statistical wind climate information due to local building design. This modification can be achieved using either wind tunnel measurement or

CFD simulation. The terrain related change explains the differences in weather station and terrain roughness and can be obtained using Eqs. (4) and (5), [47, 48].

$$\mathcal{R} = \mathcal{U} / \mathcal{U}\_{\text{us}} \tag{2}$$

$$R = \frac{U}{U\_m} = \frac{U}{U\_o} \* \frac{U\_o}{U\_m},\tag{3}$$

$$\frac{U\_o}{U\_{su}} = \frac{U\_{sto} \left(at \, \mathbf{1}.75 \, m\right)}{U\_{mtoo} \left(at \, \mathbf{10} \, m\right)} = \frac{u\_{sto}^\* \cdot \ln\left(\frac{\mathbf{1}.75 \, m}{\mathcal{Y}\_{0,sto}} + \mathbf{1}\right)}{u\_{mtoo}^\* \cdot \ln\left(\frac{\mathbf{10} \, m}{\mathcal{Y}\_{0,mtoo}} + \mathbf{1}\right)}\tag{4}$$

$$P(>U) = \exp\left[-\left(\frac{U}{R\*c}\right)^k\right] \tag{5}$$

In the assessment of the wind environment at the pedestrian level, field measurements in the real urban area (field measurement), wind tunnel tests in the scale model of the urban area and CFD simulation techniques are used. However, it is not possible to make changes at the early design stage and to measure area for urban development projects. The use of the CFD technique provides all the flow field data, while the field measurement can only be made for a few locations. But simulating the wind environment using CFD techniques is a difficult task. Regarding wind comfort at pedestrian level, as the height of the building increases, the maximum wind speed ratio increases due to the strong downwash effect, because the tall building catches the wind at a higher speed and directs it to the pedestrian level. Therefore, it creates high wind speed conditions and improves the ventilation conditions of adjacent areas of the building [49–51]. Although larger buildings increase the coverage of the low wind speed zone downstream of the building, increasing the incoming wind protection effect, the turbulence density is not significantly affected by the building's height change [48–51].

In this context, the aim of this study are examining the pedestrian level wind and comfort conditions of the existing urban texture in the settlement pattern of the Arabahmet region, which is located in the historical texture, in Nicosia Arabahmet and green line (buffer zone) texture, determining the comfortable and uncomfortable areas, examining the pedestrian level comfort conditions and wind and thermal comfort conditions, examining the effects on urban heat islands and microclimate. Similar to this, the impact of three different building porosity sizes on wind comfort surrounding a cluster of buildings and an isolated building are assessed. The findings of wind tunnel tests are used to verify the accuracy of the CFD simulation, which forecasts the wind environment at street level. The wind comfort surrounding structures is evaluated using the new wind comfort standards. From a practical standpoint, this work offers city planners and architects a solid foundation for improving pedestrian level wind comfort without sacrificing effective site use.

*Pedestrian Level Relationship between Building Forms and Streets Effects on the Condition… DOI: http://dx.doi.org/10.5772/intechopen.108735*
