What is the term for liquid flowing into the narrow clearances between two solids?

The term that describes liquid flowing into the narrow clearances between two solids is capillary attraction. This phenomenon occurs due to the adhesive forces between the liquid molecules and the solid surfaces, which are stronger than the cohesive forces among the liquid molecules themselves. When a liquid, like a soldering flux or a brazing filler metal, comes into contact with narrow spaces between two closely positioned materials, capillary attraction draws the liquid into these spaces.

This effect is crucial in many applications, such as brazing and soldering, where effective filling of gaps is essential for ensuring a strong joint. Capillary attraction allows the filler material to flow into small crevices and around components, which promotes good bonding and mechanical strength.

In contrast, surface tension primarily deals with the elastic tendency of liquids that makes them acquire the least surface area possible. Fluid dynamics refers to the study of fluids (liquids and gases) in motion, while viscosity describes a fluid's resistance to flow. These concepts are related but do not specifically define the action of liquid being drawn into small spaces between solids.