The scope of protecting public venues in the U.S. is staggering in the areas of money, time and experience at doing this sort of thing. Derivation of protection strategies for the building infrastructure will necessarily involve a combination of experiments and computer simulations to provide confidence in building design or retrofit before the needed dollars and time are committed. Computer simulation can be less costly and be performed in shorter times than experiments even when the building of interest is quite large and thus, will be used extensively now and in the future for building protection design. This paper specifically targets the accuracy and application of computational fluid dynamic (CFD) codes for prediction of mixing behavior. The ability to determine the nature, make correct identification and quantify the amount of a release from a chemical or biological weapon (CBW) relies in part on understanding the underlying physics of air propagation throughout the domain. Specifically, we must understand the rates at which a contaminant may mix throughout the domain. Turbulent mixing is a function of the range of spatial and temporal scales found in the domain, i.e., the large scale eddies (on the size of the domain) advecting the contaminant, the small scale eddies (inertial range) “mixing” the contaminant as it is being advected and the time scales corresponding to these eddy sizes. The widely used Reynolds Averaged Navier-Stokes (RANS) numerical modeling methods cannot capture the time dependent motions which are responsible for a significant amount of mixing. The Large Eddy Simulation (LES) method is based on simulating the turbulent fluctuations that can be resolved by the mesh while the smaller eddies are modeled. The LES method can produce more information about the nature of the flow field than RANS. This paper discusses the application of the LES method, specifically an LES/DES (Detached Eddy Simulation) coupled method, to simulate mixing in a realistically scaled fictitious airport. Application of the LES method such as determination of what eddy size to resolve, transient startup effects, determination of eddy turnover time and others are discussed. This research is sponsored by Department of Homeland Security under Air Force Contract F19628-00-C-0002. The views expressed are those of the author and do not reflect the official policy or procedure of the United States Government.
High pressure superheated or saturated steam line breaks in a nuclear power plant generate high speed jet flows and blast waves. The jet loads and blast wave pressures can damage critical nuclear power plant components. An accurate assessment of these effects including uncertainty quantification (UQ), is essential to confirm that design is robust enough to handle jet flows and blast waves from postulated steam line breaks. This paper presents the verification and validation of a computational model created using a commercial CFD code for making such assessments. The verification and validation process involves the steps of application space parametrization, Phenomena Identification and Ranking (PIR), CFD model lockdown, selection of validation dataset, and calculation of formal validation metrics. The Uncertainty Quantification in the actual application should include the propagated validation uncertainties from the validation test problems.
The Columbia River in Washington State is threatened by the radioactive legacy of the cold war. Two hundred thousand cubic meters (fifty-three million US gallons) of radioactive waste is stored in 177 underground tanks (60% of the Nation’s radioactive waste). A vast complex of waste treatment facilities is being built to convert this waste into stable glass (vitrification). The waste in these underground tanks is a combination of sludge, slurry, and liquid. The waste will be transported to a pre-treatment facility where it will be processed before vitrification. It is necessary to keep the solids in suspension during processing. The mixing devices selected for this task are known as pulse-jet mixers (PJMs). PJMs cyclically empty and refill with the contents of the vessel to keep it mixed. The transient operation of the PJMs has been proven successful in a number of applications, but needs additional evaluation to be proven effective for the slurries and requirements at the Waste Treatment Plant (WTP). Computational fluid dynamic (CFD) models of mixing vessels have been developed to demonstrate the ability of the PJMs to meet mixing criteria. Experimental studies have been performed to validate these models. These tests show good agreement with the transient multiphase CFD models developed for this engineering challenge.
There is a need for information on dispersion and infiltration of chemical and biological agents in complex building environments. A recent collaborative study conducted at the Idaho National Engineering and Environmental Laboratory (INEEL) and Bechtel Corporation Research and Development had the objective of assessing computational fluid dynamics (CFD) models for simulation of flow around complicated buildings through a comparison of experimental and numerical results. The test facility used in the experiments was INEEL's unique large Matched-Index-of-Refraction (MIR) flow system. The CFD code used for modeling was Fluent, a widely available commercial flow simulation package. For the experiment, a building plan was selected to approximately represent an existing facility. It was found that predicted velocity profiles from above the building and in front of the building were in good agreement with the measurements.
This paper will discuss the application of verification and validation (V&V) on both private and US government sponsored projects. Application of V&V for business and legal purposes is very tightly defined when executing a project compared to the open ended research of V&V performed in national laboratories and academia. Major purchases on the order of millions to hundreds of millions of dollars depend upon an accurate V&V if the calculation supporting the purchase involves a simulated solution or design. Examples of application will be given to illustrate the use of V&V within projects. The examples will motivate a discussion on the future needs and directions of the business industry from the larger V&V community. It is hoped that this discussion will promote greater interaction between the national labs, academia and business to help develop methodologies, consistencies and directions of effort that will support execution of the V&V process in the business sector.
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