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Decision Applications: D-5
Computational Fluid Dynamics

Computational Fluid Dynamics and Aerosol Transport Team

Fluid and thermal modeling to support various applications from atmospheric transport and dispersion to engineering systems. We have expertise in applying commercial CFD codes, such as Fluent, CFX, and Flow3D, to solve our customer's problems. We also have expertise in code development for nuclear thermal hydraulics, large-eddy simulation of atmospheric dispersion, and Lagrangian aerosol physics.

Application Areas

Atmospheric Dispersion

We have applied atmospheric large-eddy simulation codes to understand urban dispersion of pollutants. These pollutants include intentional or terrorist releases of chemical, biological, or radiological materials and also industrial facility effluents. Plume and industrial effluent modeling is an area in which our team has been actively involved for many years. Most recently we have developed modeling tools that are being used for hyperspectral sensor analysis. The plume modeling codes predict the concentration and temperature of a release as a function of space and time as the effluent flows in and around buildings and obstacles. These codes have been developed under the DOE Chemical and Biological Non-Proliferation Program (DOE-CBNP) and other "work-for-others" projects. Two main codes are being actively developed. One code is a fast-running urban dispersion model that couples a mass-consistent wind model with a Lagrangian dispersion code that computes mean wind and effluent concentrations. This work is coordinated in conjunction with Group D-3. The other is a large-eddy simulation code that provides high spatial and temporal resolution of instantaneous concentrations and fluctuations, simulating realistic variability in the effluent dispersion.

Aerosol Modeling

We have expertise in modeling indoor and outdoor aerosol transport. This expertise spans the scales from atmospheric boundary layers to urban scales and from building HVAC systems to aerosol transport in individual rooms or lab spaces.

We have been developing analytical models of the various coagulation mechanisms: in particular, inertial impaction, directional interception, diffusioporesis, thermophoresis, electrophoresis, turbulence, and Brownian motion. The analytical model has been developed using the Matlab programming environment and allows us to vary the tagging dye droplet sizes and properties to determine the relevant and dominant coagulation mechanisms and the effect on coagulation rate and/or scavenging efficiency. A Lagrangian model is also being developed to overcome some of the limitations of the analytical model. The particle model will contain all of the above coagulation mechanisms but will allow for each particle to be modeled separately and the coagulation rate to be determined from statistics of the particle population.

Thermal-Hydraulic System Code Development and Applications

Thermal-Hydraulic System Code Development and Applications

A powerful system-level analytical tool

Continuing to ensure the safety of nuclear power plants and other nuclear reactor facilities, D-5 develops and applies best-estimate thermal-hydraulics systems analysis codes.

Independent safety analyses are performed using best-estimate thermal-hydraulic codes to assess reactor safety. The TRAC/RELAP Advanced Computational Engine (TRACE) code being developed by Los Alamos and other institutions for the NRC has been used to model nuclear power plants and simulate postulated accident scenarios to show that the power plant safety systems can bring the plant to safe shut-sown conditions.

The TRACE (formerly Transient Reactor Analysis Code) thermal-hydraulic system code has been under continuous development by Los Alamos for the NRC since 1970. The TRACE code continues to evolve with an increasing understanding of complex two-phase, multicomponent fluid phenomenology. After sponsoring multiple codes for over two decades, the NRC has selected TRACE as the sole platform for future development. The Laboratory plays a key role in an ambitious multi-institutional development program designed to modernize and expand the existing code capabilities.

For more information on this project, please contact Jay Elson, 505-667-0913, or email jelson@lanl.gov.


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