Search results
In tribology, friction measurement involves the quantification of forces that resist relative motion between a solid and another substance, whether it is another solid, a mass of particles, or a fluid.
Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other. Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces. Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body.
However, all real fluids have intrinsic friction due to two effects: the weak attraction between fluid molecules (viscosity), and the transfer of momentum from fluid molecules that bounce off objects (high-speed drag).
Viscosity is a measure of the internal friction in a fluid; we examine it in more detail in Viscosity and Turbulence. In a few examples, we examine an incompressible fluid—one for which an extremely large force is required to change the volume—since the density in an incompressible fluid is constant throughout.
Learning Objectives. Explain what viscosity is. Calculate flow and resistance with Poiseuille's law. Explain how pressure drops due to resistance. Calculate the Reynolds number for an object moving through a fluid. Use the Reynolds number for a system to determine whether it is laminar or turbulent.
Nov 21, 2023 · Learn what fluid friction is and its role in science. Understand the laws, factors, and types of fluid friction with real-world examples.
The SI unit of pressure is the pascal: 1 Pa = 1 N/m 2. Pressure due to the weight of a liquid of constant density is given by p = ρ ρ gh, where p is the pressure, h is the depth of the liquid, ρ ρ is the density of the liquid, and g is the acceleration due to gravity.
