Study On Atmospheric Haze Flow Field Based On Fluent

China has the most serious haze situation in the world.Haze not only harms the health of our people,the total death rate increases 4%if the PM 2.5 increases 10ug per stere,but also brings serious economic losses in the aspects of transportation and agricultural production,among which,the fog and haze in July 2013 alone caused economic loss up to 500 million.Based on the serious haze situation in China,it is of great significance to study underlying rules to govern haze by using the flow field simulation software to simulate haze diffusion.The paper adopts the flow field simulation software Fluent to simulate haze diffusion.Based on the analysis in the literature review,the coal combustion is the culprit of the haze in China.Therefore,the paper uses the thermal power plant model to simulate haze,and the haze emission source is the flue gas discharged by the thermal power plant model.The diffusion of flue gas in the atmosphere is divided into four stages,and the most important factors affecting diffusion are wind speed and turbulence intensity.Therefore,most parts of this paper analyze the variables of wind speed and turbulence intensity.In addition,the buoyancy difference caused by the temperature difference between the flue gas and the atmosphere is the most important factor affecting the flue gas flotation stage.At the end of this paper,the influence of the temperature variable on the flotation stage is studied.First of all,the paper conducts modeling,divides the grid and conducts the initial calculation.The amount of gridding which is suitable for calculating and worked out through access connections.And the speed and temperature UDF causes the flow field to gain on the reality.And then,the paper conducts simulation calculation of flue gas.Based on the conditions of Fluent software,the flue gas is divided into two parts to conduct simulation,including polluted gas and inhalable particles.Among them,the simulation of pollutant gas is simplified as the simulation of the two main components of haze,that is,sulfur dioxide and nitrogen dioxide.The research method is to change the wind speed variable,explore its mathematical relationship in different speed conditions,and then study the common rules embodied from the mathematical relationship.It is concluded that the maximum mass fraction of the two gases decreases with the horizontaldistance.At the position of 3000m,the maximum mass fraction difference of SO₂ at the speed of 0.9m/s and 1.9m/s is 32.5 times more than 4.9m/s and5.9m/s;For the diffusion distance in the direction of YZ,each position presents increase and decrease along with the wind speed.At the position of 4000m,the distance difference achieves 6-11 times.For the simulation of inhalable particles,due to the limitation of calculation conditions,the particulate matter is simplified as the inert particle whose true density is2000kg/m³ and particle size is 2.5?m.In Fluent,the particular matter is regarded as discrete phase.The paper adopts transient calculation and adds the time term.Therefore,the study of inhalable particles is divided into two parts,including diffusion distance and diffusion concentration:In terms of diffusion distance,due to the strong fluctuation of particles,the distance difference is generally greater than that of pollution gas.At 2500s,the Y direction was about 15 times.In terms of diffusion concentration,the average hourly concentration showed the same trend as the pollution gas.However,due to the volatility of particulate matters,at the position of 2000m,the mean suspended sediment concentration of the particulate matters at the speed of 0.9m/s and1.9m/s is 3.6 times more than 4.9m/s and 5.9m/s.Each distance difference of each position is lower than pollution gas.In addition,the mean suspended sediment concentration at the position of 3000-5000m does not present downtrend along with the increase of wind speed.When the wind speed is low,the mean suspended sediment concentration at some positions even exceeds the concentration when the wind is at high speed.Finally,the thermodynamic factor is the most important factor influencing the flotation stage of flue gas.Therefore,the flow field at the temperature gradient is simulated in the end.Besides,the flotation stage is regarded as the research object,the mathematical relational graph at the temperature gradient is made,and the underlying rules are studied.With the rise of temperature,the raised height at each position tends to speed up to decrease.Among which,the distance difference of-5-0?at the position of 600m is 1.28m less than what is at the position of 1000m,and at the time of35-35?it reaches 3.94m.