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

An experimental campaign including measurement of pressure drops and velocity profiles was conducted on the pressurized flowin a commercial corrugated pipe. The results show that the empirical graphs suggested by Morris in the fifties may produce inaccurateassessments of the friction factor, in particular, for low Reynolds numbers. The experimental data was then reproduced by means of anumerical model with the large eddy simulation (LES) technique. The friction factor behavior for low and relatively high Reynolds numberswas thus investigated. The numerical simulations were in good agreement with the experimental results, showing the LES suitability topredict 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 squareerror (RMSE) were calculated, demonstrating the goodness of the numerical results. The LES model was also used to investigate the effect ofthe wall corrugation on the turbulence. Although the inner-layer was dramatically affected by the corrugation, a collapse of the mean velocityprofile was evident in the outer-layer. In the wall region, the coherent pattern of the turbulent structures appeared to be quite disaggregated inthe streamwise direction, even though they preserved the alternating arrangement of positive and negative values. Overall, both qualitative andquantitative analysis revealed that, for the range of investigated values, the streak and vortical structures were independent of the Reynoldsnumber.