结冰表面粗糙度预测与分析

Modeling of roughness dimension and distribution on the icing surface

通过对结冰表面液态水的受力分析,确定了水膜、水珠和细流特征粗糙度的大小及其之间的界限划分,发展和完善了结冰表面的粗糙度模型,开发了耦合该粗糙度模型的多步结冰计算程序;利用该程序计算结冰表面的粗糙度大小和分布特征,并对粗糙度影响下的流动和换热特性进行了计算分析;研究发现,结冰表面的粗糙度在分布是不均匀的,且随着结冰温度的降低,局部粗糙度的最大值降低,但在整个结冰过程中,局部粗糙度的最大值表现出增加的趋势;粗糙度的存在增强了结冰表面的对流换热。

It′s recognized that the roughness dimension and distribution on the icing surface influence the flow structure in the boundary layer and thus the heat transfer characteristics is affected further.Therefore, constructing an appropriate roughness model becomes a strong requirement in order to predict the ice shape accurately.In the current work,a local roughness model was developed based on the mechanical analysis of the liquid water on the icing surface.The proposed roughness model is characterized by film,beads and rivu-let.The boundaries between film,beads and rivulet are defined according to the experimental observations in references.The set of transient governing equations developed were solved numerically with the finite vol-ume method using a computational fluid dynamics （CFD）code.The mathematical model can be used to ana-lyze the effect of different icing conditions on the roughness and thus the characteristics of the heat transfer in the icing process can be obtained.Numerical results are presented to show the applicability of the developed model and can be helpful to understand the icing mechanism further.In addition,the multi-step ice predic-ting code developed in this work can be applied in anti/deicing system design directly.The predictions show that the roughness distribution on icing surface is non-uniform,and the maximum roughness is decreasing with temperature decreases.However,during the whole icing process,the maximum roughness performs an increasing trend.The convective heat transfer was enhanced due to the roughness on icing surface.