The laminar flow pattern and mixing behavior of incompressible Newtonian fluids in different modified mixer configurations were numerically investigated using Computational Fluid Dynamics (CFD) simulations in the range of Re=0.15-100. The governing equations were solved by ANSYS Fluent 14 using the second-order finite volume method (FVM) and the SIMPLE algorithm scheme. The computational model is assessed by comparing the predicted pressure drop results to empirical correlations in the literature. The effects of incorporated helical overlapped mixer elements and the diameter aspect ratio (C) on the mixing efficiency for different mixer geometries were examined and evaluated by characteristics measures of Intensity of Segregation (IOS), pressure drop, extensional efficiency, and G-factor. The performance of new modified mixers is evaluated via comparison with the standard industrial Kenics static mixer. The static mixers with modified internal geometry achieved fast mixing and better mixing quality than the Kenics mixer. Besides, an increase in diameter aspect ratio C benefited from a decrease in pressure drop within the static. The modified mixer: C=1.5 was found to have the highest mixing efficiency, concerning short mixing length with marginally higher pressure drop than the other mixers. In contrast, the mixer: C=2 is the most efficient based on low pressure drop and energy requirement with slightly greater mixing length.