The lattice Boltzmann method (LBM) is a mesoscopic numerical simulation method developed in recent decades which has good ability of dealing with complex boundary and parallel computing.The simulations were performed for back facing step flow by LBM, and the characteristics of the back step flow under different Reynolds numbers were obtained. The research results showed that, in the case of low Reynolds number, the distance between the reattachment point and the separation point became larger as the Reynolds number increased, the value of K increased with the increase of Reynolds number, while the growth rate gradually became smaller. In the case of high Reynolds number, the distance between the reattachment point and the separation point increased with the increase of the Reynolds number, and the growth rate gradually decreased. When Re=8000, the distance between the reattachment point and the separation point tended to be stable. The value of K first became larger as the Reynolds number increased, and the increase rate became smaller as the Reynolds number increased, and eventually tended to be stable. For the back step flow under high Reynolds number, the simulation was performed by the LES⁃LBM method, which was in good agreement with the previous experimental data. It showed that the LBM⁃LES model had high accuracy for simulating the back facing step flow after high Reynolds number.

The inhibition effect between 3methy4aminocinnamaldehydene5mercapto1,2,4triazole Schiff base (short for MACHMT) and cinnamic aldehyde (short for CA), 3methy4amino5mercapto1,2,4triazole（short for MACMT）on Q235 steel in the hydrochloric acid was studied by polarization curves, electrochemical impedance spectroscopy. The corrosion performance and inhibition mechanism was discussed and compared. Experiments show that stability and inhibition effeciency of cinnamic aldehyde with a 3methyl4amino5mercapto1, 2,4triazole’s complex system for Q235 carbon steel are higher than the same concentration of seats Schiff base compounds MACHMT. 

The synergistic inhibition effect between cinnamaldehyde and 3methy4amino5mercapto1,2,4triazole（short for MACMT）on Q235 steel in the HCl solution was studied by polarization curves, EIS and immersion. The influence of concentration on the corrosion performance and inhibition mechanism was discussed. The experiments show that when both cinnamaldehyde and 3methy4amino5mercapto1,2,4triazole were 1 mmol/L inhibiting system proposed good synergistic effect, inhibition efficiency could improve to more than 93%, on the Q235 steel in 0.5 mol/L HCl, 1 mol/L HCl, 2 mol/L HCl solution. In addition, increasing temperature exerted small influence on the inhibition efficiency.