Introduction
In recent years, drought has exacerbated wind pollutants in the Middle East. Pollution is damaging to the health and migration of communities. Wind erosion causes weakening of the immune system, loss of lung tissue, increased asthma in children and so on. In other words, dusting will cause widespread disruption of life and decrease individual and collective capacity, including these natural hazards in the Zabul region. Sand storms like as 120days winds and wind erosion are the result of this. The performance of this phenomenon causes a considerable decline in economic activity and inevitably requires a great deal of equipment, facilities. According to the climatic statistics, Sistan is belong to warm and dry climate. The province consists of two districts: Sistan and Baluchistan. Sistan includes Zahedan, Zabol, Zahak, Nimroz, Hamoun and Hirmand counties. This study investigates the city of Zabul. The winds in the city are constant throughout the seasons, and today's 120-day winds are the result of high-pressure western masses that blow from northwest to southeast in summer. The maximum wind in July reaches 120 km / h, which in turn drives sand flows and forms sandstorms, hillsides and sandstorms. According to estimates of the number of stormy and dusty days for a 10-year period nationwide, the Zabul region has the highest proportion nationwide with more than 1,500 days. According to the National Meteorological Organization's study, Zakah and Zabul regions had the highest number of days of environmental pollution caused by dust. Although very strong winds have low persistence, they play a major role in transporting sand. Since sand transport is the result of wind characteristics, the study area was therefore evaluated. In the Zabul region, the north and northwest wind speeds are often more than 15 kilometers per hour. The incorrect orientation of the physical form to the destructive winds and the improper shape of the buildings in accordance with the existing climatic conditions have increased the severity of the damage.
Materials and Methods
The main problem is to find the most appropriate morphological parameters of the building to control the accumulation of 120days wind. Researches which related to this issue includes studies of wind movement, experiences of ventilation in dust-tolerant areas, and the effects of dust on natural and human biomes. Zabul's Global wind shows the northwest direction of maximum wind speed. Taking into consideration the direction of the streets and the main passages of the urban fabric through aerial maps, the orientation of the masses should be selected in accordance with the climate and the direction of the wind of the area. According to studies, air conditioning is optimal when the streets are in a regular arrangement and the masses are at an angle of 20 degrees to the desired wind. There is a direct relationship between increasing wind speed and decreasing particle accumulation and with increasing wind speed the shipped sand particles are out of range. Therefore, the aim of the wind direction is to select the direction with the least amount of pollutant accumulation in addition to proper street ventilation. First, by considering the defaults of maximum wind speeds in the simulated macro mass. To this end, it is intended to create streets with different wind angles of 180, 90, and 45 degrees. In all simulations, two masses were modeled on the same side of the street at the same altitude and were investigated by rotation with respect to the prevailing wind direction. Wind velocity and intensity were selected according to the average annual wind speed of 10 m/s.
Discussion and Results
Initial results show that passages and streets that are perpendicular to the city's adverse winds, due to reduced wind speeds in the face of obstacles, cause dust accumulation and passages with angles to the adverse wind direction cause dispersal, and particles have also been hit by obstacles. Also, parallel passages with wind direction due to high speed have the least effect of sand accumulation. So among the above three modes parallel wind-driven streets have the most harmony with the predetermined default and are the best option. Since there is more sand near the surface of the earth; due to the heaviness of the wind, they do not move too far from the ground, the air flow monitoring at the junction with the building was tested in various cases and the air flow behavior around The single building was simulated 1-on the ground and 2-2 m from the ground, which resulted in zero velocity around buildings on the ground with decreasing wind velocity at the boundary of the land connection to the building. While building on a pilot will bring speed to all parts of the building close to the ground. Therefore, the distance from the ground is a criterion for controlling accumulation. Distance from ground and velocity above 2 to 4 m/s it was attempted to consider the length of the urban block, the minimum distance from the ground and the velocity above 4 m/s. Since the shape of the building complex affects the aerodynamic behavior of the wind and, conversely, the buildings are modeled in rows, and the objective is to find the E value with respect to the simulations performed in the four urban models. To achieve this goal, the buildings were selected in a row equal to 3 times the height of the buildings (12 meters) and were also simulated with distance from the ground.