Numerical simulation on vacuum pressure distribution inside a rotating cylinder

The pressure distribution inside a rotating cylinder in a vacuum chamber is investigated in the molecular flow regime. The radial pressure distributio n is estimated using the Monte-Carlo simulation method changing the rotatio n velocity at the inner radius of the cylinder (upsilon(c)) and the coeffic ient of the tangential momentum accommodation (alpha(m)). The simulation sh ows that the pressure inside the cylinder decreases as increasing upsilon(c ) due to the molecular drag effect. The center pressure goes down to 1/3-1/ 10 of the initial pressure for 20 degrees C air when upsilon(c) becomes lar ger than 1.0-1.6 times of the molecules' average velocity for a cylinder wi th both the length and the inner diameter of 100 mm. The alpha(m) is found to have little influence on the pressure distribution for the range between 0.4 and 1.0. The results suggest a possibility of making the extreme high vacuum easily but locally by means of the rotating cylinder system. (C) 199 9 Elsevier Science Ltd. All rights reserved.