What is significance of Knudsen number?

The Knudsen number is an important dimensionless quantity which allows characterizing the boundary conditions of a fluid flow.

What is L in Knudsen number?

A dimensionless parameter known as Knudsen number, K n = λ / L, where λ is the mean free path and L is the characteristic length. It describes the degree of departure from continuum. Usually when K n> 0.01, the concept of continuum does not hold good.

When Knudsen number is greater than 0.5 the flow is of the type?

molecular flow
At Knudsen numbers of Kn > 0.5 molecular interaction virtually no longer occurs. What prevails is molecular flow. In this case, the mean free path is significantly greater than the diameter of the flow channel.

What is the Knudsen effect?

When the pore diameter of the material becomes less than the average free length of the path of gas molecules, the molecules will only collide with the pore surfaces without transferring energy, this known as The Knudsen Effect (Figure 1).

What is the Mach number at room temperature?

Mach number is denoted by ‘M’. Mach number ranges from zero to infinity. It falls into several flow regimes. It is 340 m/s at room temperature.

What is aerodynamics circulation?

The circulation is defined as the line integral around a closed loop enclosing the airfoil of the component of the velocity of the fluid tangent to the loop. The fluid flow in the presence of the airfoil can be considered to be the superposition of a translational flow and a rotating flow.

What is fluid continuum?

Fluid Mechanics is a subdiscipline of Continuum Mechanics which focuses on the behaviour of fluids which include liquids and gases. Important examples for our everyday lives are water and air. Beautiful photos of fluids in motion can be found in the Physics of Fluid gallery.

What is Knudsen diffusion coefficient?

Mathematical description The diffusivity for Knudsen diffusion is obtained from the self-diffusion coefficient derived from the kinetic theory of gases: For Knudsen diffusion, path length λ is replaced with pore diameter , as species A is now more likely to collide with the pore wall as opposed with another molecule.

What circular cylinder is Strouhal number?

The Strouhal number of a stationary tube or circular cylinder is a function of Reynolds number but less of surface roughness and freestream turbulence, see Figure 2.