超声波作用下污泥内水分渗透率及有效扩散系数的分形研究

Fractal study on moisture permeability and effective diffusivity under ultrasound

对多孔介质的孔隙结构进行了分形描述,建立了多孔介质渗透率的分形模型,推导了超声波作用下多孔介质中液体的分形有效扩散系数。通过对超声波作用下污泥内部孔隙结构进行显微观察,基于分形理论分析探讨了超声声能密度对污泥内部水分渗透率及有效扩散系数的影响。研究发现,超声波作用改善了污泥内部孔隙连通性,污泥颗粒尺寸减小,孔隙尺寸增大,污泥渗透率及水分有效扩散系数均随超声作用功率的增加而逐渐递增。此外,由超声热效应引起的介质温升及超声振动激发能均加快了液体分子的振动迁移速率,进一步增大了污泥内部水分有效扩散系数。

The pore structure of porous media is described with fraetal theory, and the fractal permeability model of porous media is established. In addition, the fractal effective diffusivity of moisture in porous media under ultrasound is derived. Sludge pore structure is observed by microscope, and the effects of ultrasound energy density on moisture permeability and effective diffusivity in sludge are then discussed based on the fractal theory. The results show that the ultrasonic effect can improve the connectivity of pores in sludge; the sludge particle size decreases, and the pore size increases due to ultrasonic treatment. It is also concluded that the moisture permeability and effective diffusivity increase gradually with the increase of the ultrasound power. In addition, both temperature rising caused by ultrasound thermal effect and ultrasonic vibration excitation energy can accelerate vibration mi- gration of liquid molecules, and further enlarge effective diffusivity of moisture in sludge.