Experiment on effect of Knudsen number on micro-scale similarity flow characteristics

In order to investigate the effect of Knudsen number (Kn) on the micro-scale similarity flow characteristics, a micro-scale hole and another similar scaling-up hole with same length-to-diameter ratio were chosen, with their theroetical hole' diameters of 0.3574 mm and 3.6 mm, respectively. At the constant Reynolds number (Re), different Kn were chosen to analyze the discharge coefficients of these two holes. Results shows that at the same Re, the discharge coefficients of the two holes are in good agreement with each other while the Kn of these two holes, however, the discharge coefficients don't maintain the same when the Kn are different. As a conclusion, it is necessary to ensure the Kn of the similar scaling-up coupon is the same with the micro-scale coupon when similar scaling-up model is used to investigate micro-scale flow characteristics.