A Monte Carlo simulation of the Bernoulli principle

Effusion of an ideal gas through a small orifice when a drifting gas exists past the orifice, as well as the reverse process, are investigated through extensive two-dimensional Monte Carlo simulations. It is found that a net transport of particles takes place toward the side containing the drifting gas. Based on the model used, however, this transport of particles is caused by the drifting gas carrying away the effused particles, rather than by a pressure gradient across the aperture, as stated by the Bernoulli principle. In fact, the computer simulation results show that at zero net transport rate, the drifting gas will have a higher pressure than gas at rest. The effect of aperture size, drift velocity, and temperature are also investigated.