This document analyzes the effect of diffuser length on the performance of an elbow draft tube with a dividing pier using computational fluid dynamics (CFD). The numerical simulation was performed for three diffuser lengths (L/D1=5, 10, 15) and 13 whirl velocities from -3 to 3 m/s. Pressure and velocity contours at different sections show higher pressure and lower velocity at the outer side of the elbow and dividing pier. As diffuser length increases from L/D1=5 to 15, the pressure variation decreases and becomes more uniform throughout the draft tube. The study aims to optimize diffuser length for maximum head recovery and efficiency of the draft tube.