The present study is the first part of research into modeling flocculation processes in a tubular reactor with different width baffles. Computational fluid dynamics numerical simulation methods were used to identify intensive mixing zones and turbulent flow zones. The influence of geometry and baffle width on velocity components of the liquid flow and turbulence parameters was analyzed. The obtained results were represented as vector and contour distribution maps of the determined quantities. Flow visualization was performed to illustrate the structure and size of vortices formed behind baffles. The correctness of the numerical model was experimentally validated based on anemometric measurements using laser Doppler anemometry (LDA) method.