Numerical simulation of the effect of the geometric shape of 25% permeable series spur dikes on the flow pattern in the outer bend of a meandering channel with two different radii

Yasari Mazandarani, Mohammadreza; Rostami, Mohammad; شایسته تهرانی, ایمان; Salim Bayat, Seyed Alireza

doi:10.22034/cpj.2026.580754.1440

Numerical simulation of the effect of the geometric shape of 25% permeable series spur dikes on the flow pattern in the outer bend of a meandering channel with two different radii

10.22034/cpj.2026.580754.1440

Articles in Press, Accepted Manuscript
Available Online from 13 May 2026

Document Type : Research Article

Authors

Mohammadreza Yasari Mazandarani ¹

Mohammad Rostami ²

ایمان شایسته تهرانی ³

Seyed Alireza Salim bayat ¹

¹ M.Sc. in Civil Engineering – Water and Hydraulic Structures, Science and Culture University, Tehran, Iran

² Assistant Professor, Soil Conservation and Watershed Management Research Institute, Agricultural Research, Education and Extension Organization, Tehran, Iran

³ M.Sc. in Civil Engineering – Water Resources and Hydraulic Structures, University of Science and Culture, Tehran, Iran

Abstract

This study numerically investigates the effect of channel bend radius on the performance of 25% permeable spur dikes series in controlling the flow pattern. Two outer bends of a meandering channel with radii of 3.5 m and 4.5 m are simulated and compared under a constant discharge of 40 L/s. The two dimensional flow field is modeled using HEC RAS 2D, and spur dikes with four geometric configurations (T shaped, L shaped, inverted L, and straight I) are installed in series along each bend.

The comparison indicators include velocity distribution along the outer bend, streamline patterns, and the reduction of mean velocity relative to the no spur dikes (reference) condition. The results show that reducing the bend radius from 4.5 m to 3.5 m, while keeping the discharge constant at 40 L/s, intensifies the curvature effect and concentrates more flow towards the outer bank. Consequently, the role of spur dikes in reducing velocity near the outer bend becomes more pronounced. Specifically, for the 3.5 m radius, the reduction in mean velocity within the outer bank region is greater than that of the 4.5 m radius for all spur dikes geometries. The T shaped spur dikes exhibits the best performance in both radii, but its effect is more significant in the 3.5 m bend.

Overall, the findings indicate that in bends with smaller radii, properly designed permeable spur dikes can more effectively mitigate outer bank erosion and should be carefully considered in the design of bank protection systems

Keywords

Bank protection and erosion

Channel bend radius

HEC RAS 2D

Meandering channel

Numerical simulation

Subjects