Fluid mechanics question--slip boundary condition for gas?

In summary, a slip boundary condition is a type of boundary condition that describes the behavior of a fluid at the interface between a solid surface and the fluid. It specifies how the fluid velocity and shear stress are related at the surface, and can differ between gases and liquids due to their molecular structures. Factors such as gas viscosity, surface roughness, temperature, and pressure can affect the slip boundary condition for gas. It is important in gas flow calculations as it can significantly impact the accuracy of the results. The slip boundary condition can be experimentally determined through various techniques such as surface force apparatus, atomic force microscopy, and microchannel flow measurements.
  • #1
Yinxiao Li
46
0
In solving the Navier Stokes equation, the typical boundary condition imposed on the tangential velocity at a solid surface is that of no-slip. However, it is known that for gaseous flow there always exists a non-zero velocity near the wall, especially at relatively big Knudsen number.
Is there any good book/paper that I can get such information? In particular, I am interested in the slip velocity of nitrogen gas at Kn=0.07~0.1.
Thanks!
 
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  • #2
Google: Knudsen Number non-slip
 

1. What is a slip boundary condition in fluid mechanics?

A slip boundary condition is a type of boundary condition that describes the behavior of a fluid at the interface between a solid surface and the fluid. It specifies how the fluid velocity and shear stress are related at the surface, and whether the fluid is able to slip or stick to the surface.

2. How does the slip boundary condition for gas differ from that of liquids?

The slip boundary condition for gas differs from that of liquids due to the different molecular structures and interactions between the two states of matter. Gas molecules have more freedom of movement and are less likely to adhere to a solid surface, resulting in a larger slip length and a weaker slip boundary condition compared to liquids.

3. What factors affect the slip boundary condition for gas?

The slip boundary condition for gas is affected by several factors, including the gas viscosity, surface roughness, temperature, and pressure. Higher gas viscosity and surface roughness tend to decrease the slip length and strengthen the slip boundary condition, while higher temperature and pressure can increase the slip length and weaken the slip boundary condition.

4. Why is the slip boundary condition important in gas flow calculations?

The slip boundary condition is important in gas flow calculations because it affects the fluid velocity and shear stress at the surface, which in turn affects the overall flow behavior and can significantly impact the accuracy of the calculations. Ignoring the slip boundary condition can lead to incorrect results and predictions.

5. How is the slip boundary condition experimentally determined?

The slip boundary condition can be experimentally determined using techniques such as surface force apparatus, atomic force microscopy, and microchannel flow measurements. These methods involve measuring the fluid velocity and shear stress at the surface and comparing them to theoretical predictions based on different slip boundary conditions to determine the most accurate fit.

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