Purely elastic instabilities in a microfluidic flow focusing device
نویسندگان
چکیده
In this work, we investigate the behavior of dilute and semidilute polymer solutions flowing in a microfluidic flow focusing device, in which an inlet stream is stretched by two balanced lateral streams. By varying the flow rates in the inlet and lateral channels and their ratio, several types of flow transitions are observed and the resulting velocity fields are analyzed both upstream and downstream of the intersection. At high flow rates, the flow becomes chaotic and the path to this state depends on both the Weissenberg number and the imposed Hencky strain. The thresholds of successive elastic instabilities leading to the chaotic state are also investigated using time-resolved microparticle imaging velocimetry.
منابع مشابه
Numerical Study of Droplet Generation Process in a Microfluidic Flow Focusing
Microfluidic flow focusing devices have been utilized for droplet generation on account of its superior control over droplet size. Droplet based microfluidics addressed many scientific issues by providing a novel technological platform for applications such as biology, pharmaceutical industry, biomedical studies and drug delivery. This study numerically investigated the droplet generation proce...
متن کاملThe stabilizing effect of shear thinning on the onset of purely elastic instabilities in serpentine microflows† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sm00326e Click here for additional data file.
We determine both experimentally and numerically the onset of elastic flow instabilities in viscoelastic polymer solutions with different levels of shear thinning. Previous experiments realized in microfluidic serpentine channels using dilute polymeric solutions showed that the onset of elastic instabilities strongly depends on the channel curvature. The scaling dependence is well captured by t...
متن کاملElastic instabilities in planar elongational flow of monodisperse polymer solutions
We investigate purely elastic flow instabilities in the almost ideal planar stagnation point elongational flow field generated by a microfluidic optimized-shape cross-slot extensional rheometer (OSCER). We use time-resolved flow velocimetry and full-field birefringence microscopy to study the behavior of a series of well-characterized viscoelastic polymer solutions under conditions of low fluid...
متن کاملBuckling instabilities in dilute polymer solution elastic strands
A microfluidic oscillatory cross-slot flow is used to visualize birefringent strands in dilute polystyrene solutions with high temporal resolution, focusing specifically on reversals in the flow direction. Due to polymer conformation hysteresis, the elastic strands are slow to relax and demonstrate a compressive modulus, resulting in a “buckling instability.” An elastic loop of birefringence fo...
متن کاملCavity flows of elastic liquids: Purely elastic instabilities
Experimental observations of a purely elastic flow instability occurring in the lid-driven cavity flow of two semi-dilute polymer solutions are reported and the effect of cavity aspect ratio on the dynamical structure of the unstable flow is quantitatively investigated. The spatial and temporal characteristics of the secondary flow are measured using flow visualization, laser Doppler velocimetr...
متن کامل