| Wind-Driven Rain(WDR)is a phenomenon which raindrops are dragged by the wind flow to obtain horizontal velocity and fall obliquely during rainfall process.It is an important moisture sources that affect the durability and the hygrothermal performance of building facade materials.At present,extreme rainfall events occur more frequently and the intensity of short-term rainfall increases dramatically with the background of increasingly severe natural climate change.The exterior wall is strongly scoured by rainwater,which directly affects the waterproof and durability of the building exterior wall,resulting in the increasing loss of building disasters caused by rainwater in recent years.According to the characteristics of extreme rainfall,it is necessary to carry out the research on WDR movement and distribution of buildings and obtain the distribution law of rainfall and rain pressure,which is the theoretical basis and the fundamental problem to be solved urgently in the research of related fields and the formulation of standards.The near ground wind flow has complex turbulent characteristics,and there are a lot of multi-scale and unsteady vortices in the disturbed wind field around the building,so the raindrops carried by the wind flow will inevitably have complex dynamic behavior.It is necessary to use effective methods to evaluate the transient flow and extreme WDR distribution characteristics of buildings,so as to provide theoretical basis for the research and design of building facade waterproof,material strength and durability.In this paper,the transient WDR field is solved by fluent UDF programming established on the basis of the EM model and the large eddy simulation method,the following phenomena is simulated and analyzed on the premise of verifying the effectiveness of this numerical simulation method according to the WDR measurement work conducted by Kubilay et al..(1)the transient WDR field of typical building(the low-rise flat-roof building,the multi-story or high-rise flat-roof building and the low-rise and gable-roof building)is compared with the predicted results of RANS method and ISO semi empirical model;(2)the distribution characteristics of steady WDR effect and transient WDR effect of flat-roof and gable-roof of low-rise buildings,and the distribution characteristics of rain pressure load on the windward fa?ade and roof of buildings;(3)the WDR distribution characteristics of the windward facade and roof of the special shaped(concave,L-shaped and T-shaped)low-rise building are compared with the rectangular low-rise building,and the distribution characteristics of rain pressure load on the windward fa?ade and roof of buildings.The research shows that:(1)the distribution pattern of the catch ratio of the transient WDR field is similar to that of the steady WDR field,mean catch ratio (?) of LES method agree well with those of ISO-2009 WDR semi empirical model in the lower area on the windward facade,while mean catch ratio (?) of LES method are consistent with those of RANS method in the upper area;(2)the roof shape(the flat-roof and gable-roof)has a great influence on WDR distribution on the roof,and the rain pressure load on the windward fa?ade and roof of the building is smaller,which is equal to 1% ? 2% of the maximum pure wind pressure;(3)Compared with the rectangular building,the distribution of catch ratio on the special shaped building windward fa?ade is more uneven in the horizontal direction,the catch ratio of the "convex" area on the facade is higher than that of the corresponding area of the rectangular building,while the catch ratio of the "covered" area is lower than that of the corresponding area of the rectangular building.And different facade shapes have a greater impact on the distribution of catch ratio on the windward facade.The "convexity" area on the windward facade(roof)of special shaped buildings shows the "shelter effect" of rain pressure on the adjacent area,while the values are small and only account for 1% ? 2% of the maximum pure wind pressure. |
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