Spreading of Liquid Drops over Saturated Porous Layers

1 SPREADING OF LIQUID DROPS OVER SATURATED POROUS LAYERS 

We shall use them to study the spreading of liquid drops over thin porons snbstrates filled with the same liquid, i.e., when the thickness of the porons snbstrate, A, is assumed to be much smaller than the drop height, H, A H, (Ht. sets the scale of the drop height). We shall follow the evolntion of the liquid, both in the drop above the porous layer and inside it. 

Spreading of liquids over solid surfaces is one of the fundamental processes, with a number of applications such as coating, printing, and painting. In the previous chapter, we considered the spreading over smooth homogeneous surfaces. It has been established that singularity at the three-phase contact line is removed by the action of surface forces (see Section 3.2). 

An attempt to use Brinkman s equations for description of the flow inside the porous layer coupled with the drop flow over the layer has been undertaken in Reference 4. In the following text, the same approach is applied to investigate the spreading of liquid drops over thin porous substrates filled with the same liquid. Brinkman s equations are used for description of the liquid flow inside the porous substrate [5]. 

The kinetics of spreading of small liquid drops over thin porous layers saturated with the same liquid is investigated in this section. Theoretical consideration takes into account the kinetics of liquid motion, both in the drop above the porous layer and inside the porous layer itself. Consideration of the flow inside the porous layer is based on Brinkman s equations. 

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