Comments on “Delta-perturbation expansion for critical flow depth problem in trapezoidal channels”

Abstract

This paper discusses the study presented by Amara and Achour (2023) [10] for directly determining the critical flow depth in trapezoidal open channels. Amara and Achour (2023) [10] have focused on an analytical method based on the Delta-perturbation expansion method. There are certain drawbacks associated with the use of the Delta-perturbation expansion method to find an analytical solution of the critical flow depth for the trapezoidal open channels. The proposed complex solution by Amara and Achour (2023) [10] with many terms clearly is inaccurate for large dimensionless critical flow depth. This discussion shows that the Delta-perturbation method is not as efficient as other analytical methods such as asymptotic matching technique to develop an accurate, simple, full-range, analytical solution of the critical depth for the trapezoidal open channel sections.