Modeling ship-wake-induced sediment transport and morphological change – sediment module in FUNWAVE-TVD

Abstract

PURPOSE:This technical note documents the sediment transport module and morphological module developed in the Boussinesq wave model, FUNWAVE-TVD. The sediment transport module is based on the quasi-steady flow assumption, which is believed to be a more appropriate model for predicting sediment transport in the swash zone and ship-wake-induced shoreline erosion. It includes the suspended sediment transport and bedload sediment transport. The morphological module calculates morphological evolution based on the sediment continuity equation. This technical note also provides model validations and an example for simulating ship-wake-induced sediment transport and morphological changes. This technical note is considered an interim product that will eventually be turned into a full technical report with more validation and verification work, in particular for the case of cohesive sediment transport and morphology change. INTRODUCTION: Two types of sediment transport models have been developed under the FUN-WAVE model framework. Long and Kirby (2006) developed a coupled Boussinesq/bottom boundary layer model for surface wave-induced sediment transport and morphological changes in near-shore regions. The model is based on the curvilinear version of FUNWAVE (Shi et al. 2001)and calculates the bed-load and suspended-load transport rates using instantaneous bed shear stress in a generalized curvilinear coordinate framework. Recently, a sediment transport model for predicting nearshore seabed changes induced by co-seismic tsunamis has been developed by Tehranirad et al. (2016). The sediment transport model coupled with FUNWAVE-TVD (through multi-nesting from the Spherical coordinates to the Cartesian coordinates) successfully reproduced the deposition/erosion patterns in the Crescent City Harbor after the 2011 Tohoku tsunami. This model is based on the quasi-steady flow assumption and is particularly applicable to sediment transport induced by longer waves relative to wind wave periods.The model validations in Tehranirad et al. (2018) indicated that the quasi-steady flow-based sediment transport model is more accurate for predicting the morphological changes due to swash motion, compared with the bottom boundary layer-based sediment transport model, which is suitable for the surfzone. According to the wave characteristics of ship wakes, the quasi-steady flow-based sediment transport model such as in Kobayashi and Tega (2002) is believed to be a more appropriate model for simulating ship-wake-induced shoreline erosion because shoreline erosion occurs at the swash zone or river banks. In this study, the focus was on the ship-wakeinduced sediment transport and shoreline erosions and thus re-implemented the sediment transport and morphological modules in the present version of FUNWAVE-TVD, which has already included the ship-wake generation.The sediment transport model implemented here solves an advection-diffusion depth-averaged sediment concentration equation. It uses van Rijn's (1984) pickup function to calculate sediment ero...

On the Problem of Modeling the Boat Wake Climate: The Florida Intracoastal Waterway

“…The model has a long history of applications and testing (wave shoaling, refraction and diffraction, breaking, wave‐induced nearshore circulation, tsunami waves and coastal inundation, as well as laboratory ship‐wake generation and propagation; Kirby et al., 2013; Lynett et al., 2017; Shi et al., 2018; Shi, Kirby, & Tehranirad 2012; Tehranirad et al., 2011). Moreover, modules have been developed recently for vessel‐generated waves by different pressure distributions as well as sediment transport effects, including morphological changes (Malej et al., 2019). While other formulations, such as the Boussinesq Ocean and Surf Zone model (Roeber & Cheung, 2012) have included and tested recently ship‐wave modules with reasonable skill (e.g., David et al., 2017), the FUNWAVE‐TVD model is given preference here because of its scalable powerful MPI implementation and its flexible choice of ship‐hull representation.…”

“…Finite-element Computational Fluid Dynamics models/packages (e.g., OpenFOAM) allow for detailed modeling of vessel hull type and the resulting wakes, but the computationally intensive numerical effort is prohibitive for operational use. Because the sites impacted by wakes are typically in shallow water, Boussinesq-type models are obvious candidates (e.g., David et al, 2017;Madsen et al, 2003;Malej et al, 2015Malej et al, , 2019Nwogu & Demirbilek, 2001;Shi et al, 2016;Shi, Kirby, Harris, et al, 2012); see also reviews by Kirby (2016) and Brocchini (2013). They have become widespread with the advent of high-performance parallel computing systems, and can describe accurately wave propagation, transformation and other nearshore processes over many physical length and temporal scales in an operational setting (Malej et al, 2015).…”

“…The Boussinesq FUNWAVE-TVD implementation was selected here because it fits the shallow urbanized coastal environments and is mature and well understood (e.g., Malej et al, 2015Malej et al, , 2019Shi et al, 2016;Shi, Kirby, Harris, et al, 2012;Tehranirad et al, 2011). The model's ability to simulate wakes produced by large commercial ships has recently also been tested.…”

Ship Wakes and Their Potential Impacts on Salt Marshes in Jamaica Bay, New York

“…The morphological module of FUNWAVE calculates bed changes based on the sediment continuity equation and uses time-averaged pickup and deposition rates to compute morphological changes. The sediment transport module is based on the quasi-steady flow assumption, which is suitable for model applications to ship-wake-induced sediment transport predictions [53]. It also includes both suspended and bed load sediment transport.…”

“…Their model results were similar to observations. Model capabilities to simulate ship wakes have been successfully evaluated based on waves generated by fast vessels moving in a narrow channel with slopping beaches on both sides of the channel [49,53]. The Kelvin wake patterns behind the vessel and waves reflected from the beaches were well predicated.…”