IMECE2011-63861 PROPER ORTHOGONAL DECOMPOSITON ANALYSIS OF JAVA FLOWS FOR CROSS-FLOW CONDITIONS

ABSTRACT Jet and Vortex Actuator (JaVA) is a zero-net-mass flux device for active flow control of boundary layers and transition. JaVA produces various jets which can be used to delay flow separation or to "steer" the boundary layer velocity profile. In this study, numerical simulations of JaVA-boundary layer interactions are analyzed using Proper Orthogonal Decomposition (POD). JaVA-induced flow regimes are governed by the plate width (b), the amplitude (a) and the operating frequency (f). In this study the frequency is changed between 2/3 Hz and 8/3 Hz keeping the plate width and the amplitude constant. A commercial finite-volume-based unsteady, laminar, incompressible Navier-Stokes solver has been used to study the flow fields generated by JaVA. Then, POD is applied to time dependent snapshots of velocity fields at each operating frequency. The POD modes revealed the behavior of the flat plate boundary layer under the effect of active flow control. Traveling modes can be captured in the successive modes for high frequencies

Studying dynamic stress effects on the behaviour of THP-1 cells by microfluidic channels

Atherosclerosis is a long-term disease process of the vascular system that is characterized by the formation of atherosclerotic plaques, which are inflammatory regions on medium and large-sized arteries. There are many factors contributing to plaque formation, such as changes in shear stress levels, rupture of endothelial cells, accumulation of lipids, and recruitment of leukocytes. Shear stress is one of the main factors that regulates the homeostasis of the circulatory system; therefore, sudden and chronic changes in shear stress may cause severe pathological conditions. In this study, microfluidic channels with cavitations were designed to mimic the shape of the atherosclerotic blood vessel, where the shear stress and pressure difference depend on design of the microchannels. Changes in the inflammatory-related molecules ICAM-1 and IL-8 were investigated in THP-1 cells in response to applied shear stresses in an continuous cycling system through microfluidic channels with periodic cavitations. ICAM-1 mRNA expression and IL-8 release were analyzed by qRT-PCR and ELISA, respectively. Additionally, the adhesion behavior of sheared THP-1 cells to endothelial cells was examined by fluorescence microscopy. The results showed that 15 Pa shear stress significantly increases expression of ICAM-1 gene and IL-8 release in THP-1 cells, whereas it decreases the adhesion between THP-1 cells and endothelial cells