Study On Characteristics Of Snowdrift And Redistribution Prediction For Snowcover On Traffic Line And Bridge

Drift and transport of snow particles diffuse in natural wind,part of them suspended in atmosphere leads to drifting snow and others deposit on the ground lead to snowcover redistribution.The anisotropic gradient wind effect under ambient flows caused by ground objects may aggravate the secondary snow accumulation,or even bring transport systems to a halt.Based on the theory of Gas-Solid Hydromechanics and Computational Fluid Dynamics(CFD),prediction models of snow redistribution have been studied and developed all-sidedly.Validity and applicability of the prediction models are examined by comparing calculation results with published field measured data.Snowcover redistributions caused by fences on typical subgrades and bridge are simulated and predicted.Firstly,the existing numerical simulation methods of snowdrift are systematically summarized.Idealized spherical snow particle models are simulated by CFD dynamic mesh method.The motion behaviors of suspended snow particles in stationary air and gradient flows are investigated under different particle sizes and densities at the micro level.The research conclusions provide hypotheses and parameters for prediction models at the macro level.Secondly,a numerical prediction model for snow accumulation is developed based on the wall shear mechanism and spatial mixture theory.The results obtained from the prediction model are compared against the measured results which shows the validity of the model.In addition,the influences of skew wind on snow drifting and deposition around the ground building are also investigated.Thirdly,based on the semi-empirical model of saltation flow rate presented by Pomeroy,the source term of the governing equation for snow-phase is derived and fitted by numerical experiment.Saltation under the conditions of flat snow surface is simulated and the applicability of the proposed method is verified.A large deformation of snow surface caused by Wyoming Fence is also modeled using the prediction model.Lastly,two sets of simplified criteria are proposed to evaluate the deposition and erosion effects of different light fences,Combined with the snowdrift prediction models developed by author,take solid fences for example,the time history of snowcover redistributions on 4 types of subgrades are calculated.The secondary snow accumulation profiles on bridge deck under varied wind velocities and wind attack angles are also predicted.