Three-dimensional tracer dispersion model
Inventors
Assignees
NAVY GOVERNMENT OF United States, Secretary of • US Department of Navy
Publication Number
US-8949096-B2
Publication Date
2015-02-03
Expiration Date
2032-05-09
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Abstract
System for solving for the fully three-dimensional advection diffusion reaction (ADR) of dissolved or particulate tracers (biological or chemical materials) in aquatic environments including an input processor and an ADR tracer field processor. Results from a single execution of an ocean circulation model may be used to drive a separate ADR computer simulation and compute a tracer forecast. The velocity fields are not required to be from an ocean circulation model, they could be analysis fields derived from some other source, such as high frequency RADAR observations or satellite-based surface ocean velocity inversion/detection methods.
Core Innovation
The invention provides a system and method for solving the fully three-dimensional advection diffusion reaction (ADR) of dissolved or particulate tracers, including biological or chemical materials, in aquatic environments. The system includes an input processor that receives flow fields, bathymetric data, an initial property field, and a spatial grid, and an ADR processor that solves for the advection-diffusion-reaction of tracers, enabling computation of tracer forecasts based on either ocean circulation model outputs or other sources such as high frequency RADAR or satellite-derived velocity fields.
The problem addressed is the inefficiency and impracticality of directly coupling ADR computations with physical ocean circulation models. Such direct coupling can complicate simulations due to the complexity and uncertainty of biological and chemical reaction parameters, making multiple iterative runs computationally expensive and sometimes unfeasible due to restricted access to physical model code or computational resources. Prior art offline couplers only performed two-dimensional, surface-only advection calculations that did not conserve mass or satisfy continuity, resulting in spurious artifacts and diminished forecast reliability. There is a need for a system that efficiently uses a single execution of physical ocean or other velocity data to drive separate, fully three-dimensional ADR simulations that maintain mass conservation and continuity.
The disclosed system and method discretize the three-dimensional aquatic domain into a grid informed by bathymetry, associate velocity components with grid surfaces, and compute fluxes using first order upwind differencing. It iteratively adjusts velocity fields to ensure continuity and mass conservation across water columns with vertical layers. This approach avoids re-running physical ocean models for each ADR simulation, supports complex reaction formulations separately, and accommodates various velocity field sources, thus providing computational savings and forecasting flexibility for diverse aquatic research and forecasting applications.
Claims Coverage
The claims include one independent computer-implemented method for tracer forecasting and one independent computer system for performing the forecasting, each defining the principal inventive features of the ADR modeling approach.
Defining and processing a three-dimensional spatial grid with bathymetric data
The method/system defines a two-dimensional spatial grid for the area of interest and builds a three-dimensional grid structure using bathymetric data, where surfaces around grid points create grid cells that enable flux and velocity calculations.
Interpolating flow fields and associating velocity components with grid points and surfaces
The invention interpolates pre-selected 3D flow fields to the three-dimensional grid to define velocity at each grid point, associating velocity components with specific surfaces in the grid cells for accurate flux computations.
Computing fluid flow and total flux through grid cell surfaces using first order upwind differencing
By applying a first order upwind differencing scheme, fluid flow through each surface is calculated based on velocity components, allowing computation of total fluxes and tracer mass transport across cell boundaries.
Iterative computation and removal of residual mass fluxes to enforce continuity
Residual mass fluxes of water column layers are computed based on total flux and adjacent layers; residual velocities exceeding a continuity threshold are identified and iteratively removed from flow fields to satisfy mass conservation principles in the incompressible fluid.
Performing time-dependent advection/diffusion calculations for tracer forecasting based on adjusted flow fields
Using the continuity-adjusted flow fields, the method performs time-dependent advection and diffusion calculations to compute reliable tracer concentration forecasts over the aquatic domain.
System components for grid definition, velocity processing, flux computation, residual mass flux correction, velocity reception, and tracer field processing
The system includes specialized processors for defining spatial grids and surfaces, interpolating and adjusting velocities, computing fluxes and residuals, receiving updated velocity fields when required, and performing tracer advection/diffusion calculations to produce forecasts.
Together, these inventive features provide a comprehensive method and system that enable efficient, fully three-dimensional tracer dispersion modeling in aquatic environments, by combining spatial grid definition, velocity interpolation, flux calculation, continuity enforcement, and time-dependent advection-diffusion forecasting without requiring direct coupling with physical ocean circulation models.
Stated Advantages
Computational savings by decoupling tracer advection-diffusion computations from physical ocean model executions, allowing multiple iterations without rerunning physical models.
Ability to use velocity fields from diverse sources such as ocean circulation models, high frequency RADAR, or satellite-based observation methods.
Ensures mass conservation and continuity in three-dimensional advection-diffusion-reaction simulations, improving forecast accuracy and avoiding spurious artifacts.
Supports complex reaction formulations independently from the physical model, facilitating flexible biogeochemical and ecosystem modeling.
Documented Applications
Forecasting dissolved or particulate biological or chemical tracers in oceans, coastal domains, and estuaries using three-dimensional advection diffusion reaction modeling.
Scientific study and operational forecasting of tracer distributions in aquatic environments based on hydrodynamic conditions.
Use of diverse velocity field sources, including hydrodynamic model outputs and observationally derived velocity analyses, for tracer dispersion forecasts.
Oceanographic and aquatic research programs requiring ensemble simulations with variable reaction parameters without repeated physical model runs.
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