Based on numerical simulation

the internal hydrodynamic characteristics of membrane aerated biofilm reactor (MABR)

was investigated at different filling modes

packing densities

and circulation flow rates. With random packing

bias flow and channeling were present

causing great loss of kinetic energy at the entrance of the reactor. However

with even packing

the stability region of cross-section velocity was longer

which was more suitable for the growth of biofilm in MABR. The effect of packing density on the shell flow field of MABR was fairly remarkable

and there was an optimal value. With packing density of 30%

flow field was stable. Three-dimensional electromagnetic tachymeter was used to measure the flow field of the physical model

and the measured velocity was close to the simulated value

with error less than 10%. With circulation flow rate of 7.62 L·min-1

cross-section velocity of the reactor could be kept at 0.026 m·s-1

meanwhile maximum inlet velocity of the reactor was less than 0.20 m·s-1

which would not cause fall-off of biofilm. Stable flow field distribution accorded with the requirements of internal flow field of MABR.