For a one-componet gas flow in a channel. There are a pressure i.e density difference between two ends of the channel. There will be a mass flux. My question is how to describe this flux? it's a viscous flow or a diffusion flux? I know that Usually we use the term diffusion in multiconponent case. But we can see in literature that the term "knudsen diffusion" is used to describe the one component gas flow
The backgroun is that I am learning gas physics and I get confusd when I read some papers concerning one conponent gas flow in a single channel. Some authors says that the total mass flux across the channel can be divided into a viscous part and diffusion part.