Experimental and numerical study on the flow field and friction factor in a pressurized corrugated pipe

Abstract

An experimental campaign including measurement of pressure drops and velocity profiles was conducted on the pressurized flow in a commercial corrugated pipe. The results show that the empirical graphs suggested by Morris in the fifties may produce inaccurate assessments of the friction factor, in particular, for low Reynolds numbers. The experimental data was then reproduced by means of a numerical model with the large eddy simulation (LES) technique. The friction factor behavior for low and relatively high Reynolds numbers was thus investigated. The numerical simulations were in good agreement with the experimental results, showing the LES suitability to predict the effect of the pipe wall corrugation on the mean flow in a range of Reynolds numbers typical of engineering applications. To provide a quantitative evaluation of the numerical model, the Nash-Sutcliffe model efficiency coefficient E and the root mean square error (RMSE) were calculated, demonstrating the goodness of the numerical results. The LES model was also used to investigate the effect of the wall corrugation on the turbulence. Although the inner-layer was dramatically affected by the corrugation, a collapse of the mean velocity profile was evident in the outer-layer. In the wall region, the coherent pattern of the turbulent structures appeared to be quite disaggregated in the streamwise direction, even though they preserved the alternating arrangement of positive and negative values. Overall, both qualitative and quantitative analysis revealed that, for the range of investigated values, the streak and vortical structures were independent of the Reynolds number.