The fluid at the center of the pipe has the greatest velocity. When the viscosity is present, the fluid layers have different velocities, as figure 1(b) illustrates. Within a pipe of uniform cross-section, every layer of an ideal fluid moves with the same velocity, even the layer next to the wall, as Figure 1(a) shows. In an ideal fluid, there is no viscosity to resist the fluid layers as they slide past one another. Coefficient of Viscosity вЂ“ derivation of formula In this case, the fluid is at rest next to the walls of the tube and flows with its greatest speed in the center of the tube. Real fluids with finite viscosity are found to have flow patterns like the one shown in Figure 1(b).

If the fluid were ideal, with zero viscosity, it would flow through the tube with a speed that is the same throughout the fluid, as indicated in Figure 1(a) Examples of this type of flow can be (1) water flowing through a metal pipe in a house and (2) blood flowing through an artery or a vein. LetвЂ™s take a type of flow-say the flow of a fluid through a tube. Ideal fluid with zero viscosity vs real fluid An ideal fluid is also assumed to have steady (laminar flow) and irrotational flow. Although no real fluid has zero viscosity at normal temperatures,В some fluids have negligibly small viscosities.ДЄn incompressible, nonviscous fluid is called an ideal fluid. A fluid with zero viscosity flows in an unhindered manner with no dissipation of energy. The viscosity resists neighboring layers of fluid from sliding freely past one another. The flow of a viscous fluid is an energy-dissipating process. In contrast, gases are highly compressible with some exceptions though.

So we can approximately say, then, liquids flow in an incompressible manner. Most of the liquids are nearly incompressible as the density of a liquid remains almost constant as the pressure changes. Ideal fluid and ViscosityДЇluid flow can be compressible or incompressible. This tendency to resist a fluid flow is referred to as the viscosity of a fluid.ДЇluids like air have low viscosities, thicker fluids like water are more viscous, and fluids like honey and motor oil are characterized by high viscosity. This opposing force also exists when two adjacent layers of fluid have to move relative to each other. Similarly, a fluid flowing past a stationary surface experiences a force opposing the flow. When a block slides across a rough floor, a frictional force between the block and floor opposes the motion. This mechanism is similar to the one by which an object sliding on a rough horizontal surface loses kinetic energy.

Viscosity causes part of the kinetic energy of a fluid to be converted to internal energy. This internal friction, or viscous force, is associated with the resistance that two adjacent layers of fluid have to move relative to each other. The term viscosity is commonly used in the description of fluid flow to characterize the degree of internal friction in the fluid.

Definition of viscosity