Pulsatile flow micromixing coupled with ICED for non-Newtonian fluids Mehmet Melih Tathsoz, cetin Canpolat

WOS: 000444664200002The most biofluids/polymers, which are extensively used in lab-on-a-Chip devices exhibit non-Newtonian characteristics, whose mixing behaviors become crucial for the most engineering applications. For this purpose, the present numerical study investigates the performance of pulsatile flow micromixer coupled with induced charge electro-osmosis (ICED) for non-Newtonian fluids, such as power-law and Carreau. The mixing characteristics of Newtonian fluids are also presented and compared to non-Newtonian cases. The straight micro channel geometry is modified using rectangular obstruction with various heights to increase stirring performance for non-Newtonian fluids. The magnitude of the external electric field, the frequency of pulsatile flow and the width of rectangular obstruction are systematically varied for a comprehensive parametric evaluation. Time dependent patterns of streamline and corresponding concentration maps are illustrated for qualitative presentation. Moreover, mixing index values are plotted versus obstruction width, the frequency of pulsatile flow and imposed electric field strength for quantitative analysis. It is observed that pulsatile flow with ICE) yields reasonable performance for all type of fluids. However, a rectangular obstruction is required to obtain maximum performance of mixing of non-Newtonian fluids for the given time, t = 10 s and length, l = 0.7 mm. It can be reported that rectangular obstruction has a significant effect on mixing performance for current conditions.Cukurova University Scientific Research OfficeCukurova University [FBA-2017-7960]This work is supported by Cukurova University Scientific Research Office financially under contract no FBA-2017-7960

EFFECT OF YAW ANGLE ON THE FORMATION OF VORTEX BREAKDOWN OVER THE DIAMOND WING

WOS: 000277481000009In this study, the flow structure close to the surface of the non slender diamond wing was investigated both qualitatively and quantitatively using dye visualization and the 3-D Particle Image Velocimetry (PIV) technique. The flow structure and formation of the vortex breakdown were studied by varying the yaw angle of the wing within the range of 0 degrees <=theta <=<15 degrees for the angle of attack of alpha=7 degrees and Reynolds number of 10 000. After a certain distance from the wing apex, a stagnation points and onset of vortex breakdowns took places on the central axes of spiral vortices that occurred over the wing surface for the angle of attack of alpha=7 degrees. When the yaw angle was increased the locations of vortex breakdowns approached to the wing apex, but, the other one moves towards the trailing edge

Control of the flow past a sphere near a flat wall using passive jet

In the present investigation, interactions between the vortices shedding from a single sphere and the boundary layer flow over a flat plate with various gap ratios have been investigated at Re = 5000 using the techniques of dye visualization and Particle Image Velocimetry. A passive jet has been created to control the flow past the sphere by a hole drilled into the sphere from the forward stagnation point to the rear of the sphere with various diameters. The results show that the complex flow downstream of the sphere, which is occurred from the combination of 'Carman vortex street and the boundary layer over the flat plate can be controlled by a passive jet. Because the jet flow interrupts periodicity of the vortices shedding from the sphere by supplying fluid flow into the wake with relatively high velocity. Presence of the hole significantly attenuates the magnitudes of the turbulence characteristics. Furthermore, the magnitudes of the turbulence characteristics decrease with increasing the hole diameter depending on the location of the sphere in the boundary layer. However, a larger hole diameter can result in higher turbulence levels in the region of the passive jet. Hence, the effectiveness of the each case (the diameter of the hole) changes with the location of the sphere over the flat plate.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [109R028]; Scientific Research Projects Office of Cukurova UniversityCukurova University [AAP20025]; Selcuk University's Scientific Research Project OfficeSelcuk University [11201040]; DPT projectTurkiye Cumhuriyeti Kalkinma Bakanligi [2009K12180]The authors would like to acknowledge the funding of The Scientific and Technological Research Council of Turkey (TUBITAK) under contract No:109R028, Scientific Research Projects Office of Cukurova University Contract No: AAP20025, Selcuk University's Scientific Research Project Office Contract No: 11201040, and DPT project Contract No: 2009K12180