Slip Flow between Two Parallel Plates

In the previous chapter, we have discussed about the simplification of N-S equation on the basis of nondimensionalization of the governing equation. Let us relook at the simplification of N-S equation on the basis of the order of magnitude approach. For the momentum equation of the flow between two parallel plates, it may be approximated as 

We can also use the estimate shown in equation (3.66) considering the compressibility effect for simplification as follows. 

substituting Kn expression into equation (3.68), we have 

The above-mentioned two estimates, that is, equations (3.67) and (3.71), are similar except the presence of which is usually smaller than unity. 

Therefore, for low Re flows Re 0( 1)) in large aspect ratio channels Ljht l), the inertial effects in the momentum equation can be neglected. 

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