Resistance in steep open channels due to randomly distributed macroroughness elements at large froude numbers

Suresh Kumar Thappeta, S. Murty Bhallamudi, Peter Fiener, Balaji Narasimhan

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Energy loss in a steep open channel due to randomly spaced spherically shaped macroroughness elements such as boulders was investigated using a three-dimensional fluid dynamics solver. First, a relationship for energy loss at large Froude numbers due to a single boulder was derived as a function of flow rate, flow depth, and boulder diameter. Nondimensional energy loss increases with Froude number and decreases with the relative submergence. However, the exponents in the power law relationship are different for three different ranges of submergence ratio: < 0.5, 0.5-1.0, and > 1.0. The energy loss attributable to a cluster of boulders depends on cluster density, Froude number, and submergence ratio. For the same number of boulders, energy loss decreases as cluster density increases. However, variation in the pattern of boulder arrangement has only a marginal effect (< 4%) when the submergence ratio is more than 0.5. The simple procedure proposed for estimating energy loss due to a cluster of randomly distributed boulders of equal size predicts energy loss within 10% accuracy.

Original languageEnglish
Article number04017052
JournalJournal of Hydrologic Engineering - ASCE
Issue number12
StatePublished - 1 Dec 2017
Externally publishedYes


  • Boulder spacing
  • Boulders
  • Computational fluid dynamics
  • Energy loss
  • Mountainous channels

ASJC Scopus subject areas

  • Environmental Chemistry
  • Civil and Structural Engineering
  • Water Science and Technology
  • General Environmental Science


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