High-resolution SPH simulations of rocky shores: understanding and modeling of sub-grid scale proces
Abstract
Safe and effective Naval expeditionary operations in the littoral zone directly depend on the availability of the robust and accurat,e forecast of the relevant environmental parameters, such as bathymetry, waves, and currents. Over the past several decades, extens,ive research by the coastal and ocean scientific community has led to the development ,els across the inner-shelf and gently sloping sandy beaches.However, the application and performance of these forecast models on roc,ky shores are unknown. This is because of the presence of complex sea-floor topography features of various scales, O(cm) to O(km), w,hich considerably changes a wide range of non-dissipative, such as wave reflection and scattering, and dissipative, such as form dra,g and wave breaking, wave transformation processes, as well as the resulting wave-driven circulation and turbulence, in rocky shores, compared to well-studied sandy beaches.I propose detailed high-resolution Smoothed Particle Hydrodynamics (SPH) modeling of rocky s,hores, with spatial resolutions of O(cm), to understand the interaction of surface gravity waves with complex sea-floor topography f,eatures of scales 0.1 - 10 m, steep slopes, and abrupt bathymetry changes such as surge channels. My focus is to gain a better unde,rstanding of the relevant dissipative processes (and forcing) due to form drag and wave breaking, as well as the associated effects,on wave-driven circulation and turbulence across representative rocky shores. A related task is to develop robust parameterizations,for these sub-grid scale processes for use in wave and hydrodynamic forecast models. The long-term goal of the proposed work is to e,xpand the domain of existing nearshore forecast models to include the rocky coast environment.The proposed modeling framework is cha,racterized as a 3D mesh-free Computational Fluid Dynamics (CFD) modeling with a Large Eddy Simulation (LES) resolution which directl,y handles any complex topography features, including vertical and surface-piercing rocks, and resolves the formation of multi-valued, free surface and the generation of vorticity during wave breaking process and wave-topography interaction. The model resolves the,instantaneous free surface elevations as well as the velocity and dynamic pressure fields associated with currents, waves, and energ,etic turbulent eddies. Thus, the corresponding 3D stress (forcing) terms in the turbulence-averaged (parameterized in wave-resolving, RANS models such as NHWAVE) and wave-averaged (parameterized in ROMS, COAWST and DELFT-3D) momentum balances as well as the corresp,onding energy dissipation terms in the wave action density balance (parameterized in SWAN and WW3) could be directly obtained from t,he model results. The overall effect of these terms could be also estimated using the predicted surface wave field as typically done, in large-scale field observations.The proposed work will complement the ongoing ONR-sponsored MURI project on rocky shores, ``ROXSI,: ROcky shores eXperiments and SImulations . The proposed simulations are designed (based on discussions with the ROXSI PIs) such t,hat they will benefit the design and interpretation of the proposed small-array observations in ROXSI. Also, the proposed work will,benefit from the observations in regard to realistic modeling of representative rocky shores.The proposed research has high potentia,l for significant and expeditious impact on Naval capabilities by improving our knowledge of rocky shore dynamics and extending exis,ting nearshore forecast models to rocky shores with skill comparable to that for sandy beaches.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 13, 2022
- Source ID
- N000142212566
Entities
People
- Morteza Derakhti
Organizations
- Office of Naval Research
- United States Navy
- University of Washington