Numerical Simulation About Distribution Of The Dust Pollution By The Moving Car

In recent years, environmental pollution problem caused by vehicle emissions havebecome increasingly prominent, and PM₁₀regularly becomes the primary pollutant inmany cities due to the rapid increase of vehicle population. Researches have shown that30%⁵0%of the PM₁₀are from traffic dust. Three methods, such as wind tunnel test,field test and numerical simulation, are adapt to study the vehicle dust emissions now.Considering long cycle of wind tunnel tests and the uncontrolled factors in field tests,numerical simulation method is investigated to study the vehicle outflow fields and thePM₁₀concentration distribution.In this paper, numerical simulations are conducted by the fluent software to obtainthe certain turbulent model proper for the simulation of vehicle outflow fields throughthe comparison with wind tunnel test results. And simulated the vehicle outflow fieldsof2D by dynamic grid technology, analyzed the flow condition of car tail wind. Thereare many factors affect the PM₁₀dust emissions from vehicles，based on simulated thevehicle outflow fields of3D combined analysis with MRF model，investigated theinfluences of gravity and wheel rotation to the PM₁₀concentration，studied the effects ofcar speed and dust loading to the PM₁₀dust concentration，Further single vehicle andmulti-vehicle PM₁₀dust emissions intensity are analyzed.The results show that RNG k-ε turbulent model is more suitable for the car outflowfield simulation than standard k-ε turbulent model; The dynamic simulation of theoutflow field can be achieved by setting moving coordinate system; Along with thedevelopment of the car tail wind, the car outflow field experiences the process ofdisorder, horseshoe vortex and a pair of trailing vortices, a pair of trailing vortices with high intensity. Among this process the vortex centers expand outward gradually.Keeping other parameters constant, the gravity has little influence on the PM₁₀dustaverage density, while the wheels rotating or not will have great difference on the PM₁₀dust distribution,so in the simulation of PM₁₀dust, we can negligible gravity but mustconsider the rotation of the wheels；The vehicle speed is proportional to the dustmigration rate and linear to the dust height distribution; Another, the dust loading isproportional to PM₁₀dust average concentration In the X and Z sections, and the samephenomena in the Y section except area of the dust not arrived. Vehicle PM₁₀dustemissions intensity obey Lorentz distribution under different speeds.Through the data fitting, some equations are obtained, which can reflect therelationship of the vehicle speed and the PM₁₀dust height, and PM₁₀dust emissionsintensity models about the single vehicle or multi-vehicle are also established.