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1. NUMERICAL UNDERSTANDING OF THE SELF-INDUCED OSCILLATION OF FLOW PAST THE OPEN CAVITY WITH A STORE.

Author

SI, HAI-QING and WANG, TONG-GUANG

Subjects
TURBULENCE, NUMERICAL analysis, NAVIER-Stokes equations, COMPUTER simulation, VISCOSITY, FOURIER transforms, SPECTRAL energy distribution, ALGORITHMS, REYNOLDS number
Abstract

The flows around a typical open cavity with a store are numerically simulated in this paper. A fully implicit unfactored method is employed in the solver of RANS equations, where the S-A turbulent model is implemented to calculate the turbulent eddy viscosity. The flow-induced oscillation of the free shear layer around the cavity lip is captured and analyzed. Comparisons for the different cases of the cavity flow are made. The calculated results show that the pressure fluctuation is pertinent to the different positions of the store inside the cavity. The power spectral density (PSD) of the pressure by fast Fourier transformations (FFT) is also displayed in the paper. For the Rossiter's oscillatory mode, the numerical results compare well with the experimental data. [ABSTRACT FROM AUTHOR]

Published
2010
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2. Modeling bacterial clearance using stochastic-differential equations

Author

Aleksandar Jeremic and Ashraf Said Atalla

Subjects
Stochastic Processes, Models, Statistical, Materials science, Capillary action, Differential equation, Numerical analysis, Mechanics, Thermal diffusivity, Models, Biological, Bacterial Load, Capillaries, Capillary Permeability, Condensed Matter::Soft Condensed Matter, Physics::Fluid Dynamics, Stochastic differential equation, Animals, Humans, Computer Simulation, Fokker–Planck equation, Boundary value problem, Statistical physics, Navier–Stokes equations, Algorithms
Abstract

Capillary - tissue fluid exchange is controlled by the blood pressure in the capillary and the osmotic pressure of blood (pressure of the tissue fluid outside the capillaries). In this paper, we develop a mathematical model to simulate the movement of bacteria into and within a capillary segment. The model is based on Fokker-Planck equation and Navier-Stocks equations that accounts for different boundary conditions. Also, we model the transportation through capillary walls by means of anisotropic diffusivity that depends on the pressure difference across the capillary walls. By solving the model with a numerical method, it was possible to predict the concentration of bacteria at points within the capillary. However, numerical analysis consumes computational time and resources. To efficiently simulate the bacterial clearance, we propose a segmentation model that is based on breaking the capillary network into smaller sections with pre-defined properties in order to reduce the overall computational time. The proposed model shows a great reduction in computational time and provides accurate results when compared to the numerical analysis.

Published
2010