Multiscale modeling of internal waves and turbulence at rough, realistic topography with SOMAR-LES
Multiscale modeling of internal waves and turbulence at rough, realistic topography with SOMAR-LES
Abstract:
The Stratified Ocean Model with Adaptive Refinement (SOMAR) is a modeling framework with the flexibility of adaptive mesh refinement at localized regions with high gradients. Several test cases including the lock-exchange problem, solitary wave propagation and internal tide generation have been previously considered to validate the method. Local refinement of the
grid allows the solver to achieve highly accurate results with substantial reduction in computational cost. Recently, SOMAR-LES has been developed wherein a three-dimensional, body-conforming Large Eddy Simulation (LES) model that resolves turbulence scales is coupled with SOMAR to accurately represent small scale turbulence as well as its effect on flow evolution at large scale. The coupling is two-way: LES is driven with large scale forcing, and SOMAR receives feedback in the form of eddy viscosity, diffusivity and sub-grid scale fluxes. This novel multi-scale modeling technique is applied to study the near- and far-field baroclinic response when the oscillating barotropic tide interacts with underwater topography. Numerical simulations are performed with SOMAR-LES to examine the flow at Kaena ridge, a steep supercritical generation site, where the topographic length scales are of O(100 km), and the barotropic forcing corresponds to a small outer excursion number (Ex = U0/ω ≈0.01) and small Froude number (Fr = U0/N h0 ≈0.006). Results are compared against high-resolution LES of the flow at the ridge in a scaled-down LES to assess turbulence representation in the coupled model. The SOMAR-LES results are compared with HOME data, and used to quantify baroclinic energy conversion and internal wave properties such as the radiated wave flux and modal composition.
grid allows the solver to achieve highly accurate results with substantial reduction in computational cost. Recently, SOMAR-LES has been developed wherein a three-dimensional, body-conforming Large Eddy Simulation (LES) model that resolves turbulence scales is coupled with SOMAR to accurately represent small scale turbulence as well as its effect on flow evolution at large scale. The coupling is two-way: LES is driven with large scale forcing, and SOMAR receives feedback in the form of eddy viscosity, diffusivity and sub-grid scale fluxes. This novel multi-scale modeling technique is applied to study the near- and far-field baroclinic response when the oscillating barotropic tide interacts with underwater topography. Numerical simulations are performed with SOMAR-LES to examine the flow at Kaena ridge, a steep supercritical generation site, where the topographic length scales are of O(100 km), and the barotropic forcing corresponds to a small outer excursion number (Ex = U0/ω ≈0.01) and small Froude number (Fr = U0/N h0 ≈0.006). Results are compared against high-resolution LES of the flow at the ridge in a scaled-down LES to assess turbulence representation in the coupled model. The SOMAR-LES results are compared with HOME data, and used to quantify baroclinic energy conversion and internal wave properties such as the radiated wave flux and modal composition.