Computational fluid dynamics (CFD) is a powerful numerical tool that is becoming widely used to simulate many processes in the industry. In this work, a study of the STIRRED TANK with 7 types of concave blade with CFD was presented. In the modeling of the impeller rotation, sliding mesh (SM) technique was used, and RNG-k-ε model was selected for turbulence. Power consumption at various speeds in the single phase, mean tangential, radial and axial velocities in various points, effects of disc diameter and thickness, and mixing time were investigated. The optimum concave impeller was selected, and the effect of tracer feed position and probe location was investigated on it. Results suggested that power consumption was exactly dependent on impellers’ scale and geometry; results are in good agreement with the experimental data, and turbulent flow is relatively independent of Reynolds number. Power number increases by increasing disc diameter for both concave and Rushton, and concave´ s power is relatively independent of disc thickness; however, increasing it decreases Rushton´ s power. The data revealed that the power number was 2. 3± 0. 3 for a blade angle of 40° , whereas, for blade angles 25° , 50° , and 55° , it was 43 % lower and 57 % and 43 % higher, respectively.