Wide variability exists in the prediction of intracranial aneurysm WSS. While segmentation and CFD solver techniques may be difficult to standardize across groups, our findings suggest that some of the variability in image-based CFD could be reduced by establishing guidelines for model extents, inflow rates, and blood properties, and by encouraging the reporting of normalized hemodynamic parameters.

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Abstract. The here presented work is part of a CFD challenge investigating the potential for computational fluid dynamics (CFD) simulations to predicted pressures and flows in an aortic coarctation during stress when conditions for the rest case are known. In our approach, we choose to couple a three element Windkessel model to the outlet boundary conditions. Good reproducibility of flow and pressures for the rest case were achieved. In the stress case, where only the inflow boundary condition was changed, baseline pressure was too high, indicating that the total resistance in the Windkessel models may need to be reduced. This would correspond to dilating the blood vessels as might be the result of a pharmacological stress test. Future work is needed to develop an optimization strategy to tune the Windkessel data for matching the clinical results.

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.

The purpose of this work was to validate and apply a commercial computational fluid dynamics code with a hybrid RANS/LES turbulence computational model for a flow past a bluff body ultimately to help in the design of the caisson anchoring system during construction of a new adjacent span of the Tacoma Narrows Bridge.

The newly constructed Tacoma Narrows Bridge Piers represent large concrete floating caissons during their construction. For designing their mooring system the current force applied on the caissons in the Narrows must be known. The flow field around the caisson is highly complex and the calculation of the current load on the caisson by analytical means is difficult. On the other hand, model tests suffer from the distortion in the Reynolds number. Therefore, a two-prong approach was undertaken. Besides the fixed model test of the caissons for current forces, a CFD analysis of the flow around the caisson is chosen. A three-dimensional CFD approach is considered more appropriate than a two-dimensional one, since the bottom contour at the site is irregular and water depth is rather shallow. This paper discusses the CFD method and the results obtained from such analysis. The numerical analysis was carried out in both ebb and flood flow of the tidal current in the basin. One of the difficulties of the computational method is the very high Reynolds number encountered by the large current and large size of the caisson. The analysis is performed in both model and full scales so that the difference in the results may be investigated. Also, since the model test data are available, comparisons are made between the CFD and model test results on the drag and lift forces on the caisson.

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