Experimental Investigations On The Dust Emission Mechanisms Over Different Surfaces In Wind Tunnel

Dust emission is an important part of global dust circulation system,the emitted dust particles are the most important source of global dust aerosols by wind erosion,these dust aerosols not only change the radiation balance of ground and atmospheric by absorbing and scattering the radiation of the ground and solar radiation profoundly,thus cause the change and adjustment of the global climate,but also they have a significant effect on air quality as well as the human life and health in the world.However,we are still lack of profound knowledge and understanding about dust emission on different surface in varying conditions currently.There are many kinds of models to describe dust emission on the surface at present,either based on the summary of field observation data,or focus on the description of physical process,but the reliability and applicability of these models are still lack of systemic validation by wind tunnel experiment.Based on the simulation and measurement to the process of dust emission in the wind tunnel,to analyse the main mechanisms and influencing factors which cause dust emission under different conditions,and then compare and verify several kinds of typical dust emission model.Results show that the maximum flux of aerodynamic entrainment can achieve even more than the dust emission flux caused by saltation bombardment,in the absence of other factors,the process of aerodynamic entrainment can only maintain the shorter time(about three minutes);Flow conditions,surface particle motions(saltation and creep),soil dust content and ground obstacles all strongly affect dust emission,causing dust emission rate to vary over orders of magnitude,and the surface plastic pressure has a great influence on the process of aggregates disintegration;Surface dust supply limit is a major reason for restricting aerodynamic entrainment,which has a certain influence on the weak saltation bombardment at the same time;While aerodynamic entrainment is suppressed by dust supply limit,surface renewal(surface particle motions of saltation and creep)is found to be an effective pathway to remove the supply limit;Effective surface renewal can maintain aerodynamic entrainment and the efficiency of saltation bombardment;The predicted results of Gillette & Passi(1988)model,Lu & Shao(1999)and Shao(2004)models have good agreement with the experimental measurement results.The predicted results of Kok(2014)model fit the best with the experimental measurements,and the predicted results of Marticorena & Bergametti(1995)model are relatively poor to the others.Through analysing the wind tunnel experimental data of this paper on the current dust emission mechanisms and empirical parameter model or physical mechanism model,and the results show that aerodynamic entrainment is closely related to the surface renewal,the mechanism of surface renewal should be include in future dust emission model through the further research in order to predict dust emission flux more accurately.