Feasibility of using computational fluid dynamics for analysis of flow in an orbiting dish.

摘要

The oscillatory flow provided by an orbital shaker table correlates somewhat to the pulsatile flow seen in the human vasculature. This parallel allows for the use of the orbital shaker table in a large range of biomedical research. However, the fluid dynamics is not well characterized in this system.;This research employed the computational fluid dynamics (CFD) package FLUENT in an effort to better understand the fluid dynamics in an orbiting dish. This work was performed at low resolution as a first attempt to examine the fluid flow characteristics. The first objective was to determine the time required to reach a steady state. This was found to occur within four orbits of the dish.;The shear stress on the bottom surface of an orbital dish was then investigated and compared to previously published scalar functions. An equation used in two cases by Ley et al. (1989) determined shear to be 2.76 dyne/cm 2 and 3.12 dyne/cm2 respectively. These systems had Stokes Numbers of 2 and 2.5, Froude Numbers of 0.7 and 0.8 and Slope Ratios of 0.4 and 0.3 respectively. When modeled in FLUENT the cases showed the magnitude of shear stress in the center of the dish to be 0.67 dyne/cm2 and 1.11 dyne/cm2 respectively. The average shear stress on the bottom of the dish for the same cases was determined to be 0.39 dyne/cm 2 and 0.85 dyne/cm2 respectively. More revealing, the shear was found to be uneven across the bottom of the dish with maximum shear near the peak of the fluid wave.;Next, cases were simulated across ranges of dimensionless Stokes Number, Froude Number, and slope ratio at low resolution to determine the feasibility of using FLUENT to observe transitions. Each case was run at a constant Reynolds Number of 100 to maintain laminar flow. A Stokes number transition is evidenced by a lag in the location of the fluid peak relative to the location of the dish. When a gap in the leading edge of the fluid is observed, a Froude number transition has occurred. A large free surface slope resulting in a dry area forming on the bottom of the dish is indicative of a Slope Ratio transition. These transitions were positively identified at low resolution when changing one dimensionless number while keeping the others constant.