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Investigation of Momentum Correction Factor in the Swash Flow

Zhu, Fangfang; Dodd, Nicholas; Larson, Magnus; Zhang, Jie

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Fangfang Zhu

Professor of Coastal Dynamics

Magnus Larson

Jie Zhang


Swash flows are commonly modeled using the nonlinear shallow water equations (NSWEs). In the derivation of the NSWEs, directly from depth-averaging the Navier-Stokes equations, a so-called momentum correction factor, β, emerges. In this study we present a numerical model of the NSWEs that includes β, which is allowed to vary in space and time, and feedback onto the flow. We apply this model to a swash flow, by making use of the vertical flow structure calculated by use of the log-law boundary layer and free flow region. We thereby examine its influence on the swash-flow predictions of a dam-break swash event described in the literature. The numerical results show that the momentum correction factor has a significant effect on the shoreline motion, and flow adjacent to the shoreline, which results in an overprediction of the shoreline with respect to the standard (β = 1, NSWE) approach. Given that consideration of β should yield a more complete description of the swash dynamics, the implication is that the log-law boundary layer model does not describe the flow structure in the swash tip region well. The implication of this is that to achieve accurate modeling at the flow uprush tip, at which point the largest bed shear stresses are typically exerted, a different submodel is required in that vicinity. Equally, it suggests that classical NSWEs also cannot describe the flow at the tip well, and that accurate prediction is achieved despite this inherent deficiency.


Zhu, F., Dodd, N., Larson, M., & Zhang, J. (2022). Investigation of Momentum Correction Factor in the Swash Flow. Journal of Waterway, Port, Coastal, and Ocean Engineering, 148(6),

Journal Article Type Article
Acceptance Date May 24, 2022
Online Publication Date Sep 7, 2022
Publication Date Nov 1, 2022
Deposit Date Jun 15, 2022
Publicly Available Date Sep 7, 2022
Journal Journal of Waterway, Port, Coastal, and Ocean Engineering
Print ISSN 0733-950X
Electronic ISSN 1943-5460
Publisher American Society of Civil Engineers (ASCE)
Peer Reviewed Peer Reviewed
Volume 148
Issue 6
Keywords Ocean Engineering; Water Science and Technology; Civil and Structural Engineering
Public URL
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