DOI: https://doi.org/10.36347/sjet.2025.v13i07.001

Pages: 424-435

The turbulent flow behavior in a pipe with sudden expansion has been studied in this work using Computational Fluid Dynamics (CFD) techniques. Analysis is conducted to study the influence of Reynolds number, expansion ratio and their interaction on the two critical parameters, recirculation length and pressure drop. 15 CFD simulations were performed at varying Reynolds numbers from 5000 to 25000 and expansion ratios from 1.5 to 2.5. Flow parameters were found to vary considerably as shown by descriptive statistics, higher Reynolds numbers correlated with increased pressure drop and longer recirculation zones. Reynolds number was found to have a strong positive correlation with pressure drop (r = 0.934) and moderate positive correlation with recirculation length (r = 0.655) by means of correlation analysis. Strong correlation was observed between expansion ratio and recirculation length (r = 0.756), but weak correlation was observed between expansion ratio and pressure drop (r = 0.323). ANOVA tests of the effects of Reynolds number and expansion ratio indicated that neither had statistically significant effects at the 95% confidence level, but significant (p < 0.001) linear relationships were found between Reynolds number and pressure drop and recirculation length (p = 0.008). Further group means analysis showed progressive increase in recirculation length with increasing Reynolds numbers and increasing pressure drop with increasing expansion ratios. Learnings drawn from these findings give a robust quantitative framework to understand the complex interaction between flow velocity, pipe geometry and the separation phenomenon. Such results are valuable for designing a more efficient piping system in the industrial or engineering applications.