Under the same shear stress, different fluids deform at different rates. Viscosity, i.e., is the property of a fluid, due to cohesion and interaction between molecules, which offers resistance to shear deformation. It is the resisting property of a fluid to shear force. The viscosity of the fluid is defined as the property of the fluid that offers resistance to the movement of one layer of the fluid over another adjacent layer of the fluid. There is some sort of resistance to the flow of various layers of the fluid, which is offered by the adjoining layers, this property of the fluid is called the viscosity of the fluid. This shows that as it moves from the top layer to the bottom layer the speed of the flow of fluid reduces. Liquids such as water or oil flow as layers on the surface, with the top layer moving at the fastest speed and the bottom layer moving at a slower speed. The shape of such a concave or convex surface is known as the meniscus. Surface tension occurs during the gas-liquid interface, but if that interface comes into contact with a solid surface like the walls of a container, the interface usually decreases near or below that surface. In non-wetting liquids (mercury) capillarity depression is caused. Liquids, such as water, which wet a surface cause capillarity rise. The rise or fall of liquid in small diameter tubes is due to molecular attraction is called capillarity. The most common interfaces and values of S for the clean surface at 20° Surface tension = Force per unit length in N/m.

Surface tension has the unit of force/unit length or energy/unit area. This liquid property is known as surface tension. Adhesion allows it to adhere to another body.Īt the interface between a liquid and a gas, that is, in a liquid, the out-of-equilibrium force between molecules creates an imaginary surface layer, which exerts a tension force on the surface.Cohesion allows a liquid to resist tensile stress.Liquids have both cohesion and adhesion and both are forms of molecular attraction. It is also described as the tensile force on the surface of the liquid in contact with a gas, such that the contact surface acts as a membrane under tension. The surface energy per unit area of the interface is known as the surface tension coefficient of surface tension. Surface TensionĪ liquid creates an interface with the second liquid or gas. Read Also: What are the Types of Fasteners? Their Uses & Examples 6.

Viscosity definition fluid mechanics