Keyur Kanade
Ansys Employee
The primary idea behind the continuum assumption is that Fluid is continuously divisible and we do not have to concern ourselves with individual molecules. This assumption is valid under normal conditions. However, it very quickly breaks down when the characteristic length scale (dimension) of our problem is on the same order as the mean free path of the fluid molecules. For example, we must abandon the concept of continuum in case of rarefied gases. The validity of continuum assumption can be verified using the Knudsen Number.