STREAMER FORMATION IN PARTICLE LADEN POLYMERIC FLOWS

Particle laden polymeric flows are of interest to the fluid mechanics community due to the possibility of flow induced aggregation and structure formation. Here, we show that when particle laden polymeric suspensions flow through an annular area at moderate Reynolds numbers (similar to 10) and Weissenberg numbers (similar to 10(-2)-10(-1)), it can result in formation of flow induced structures. Specifically, the particle can aggregate in the form of thin slender, flexible structures called streamers. The name `streamer' is inspired by their slender morphology which is similar to bacterial streamers formed in bacterial aggregation subjected to continuous hydrodynamic flow. In the present work, polyethylene oxide (PEO) and dry gram flour has been used to create particle laden polymeric fluid suspension. The Taylor-Couette geometry has been modified by employing a stationary needle in the annular space to study the effect of varying hydrodynamic conditions on streamer formation and their morphology. Experimental observations show that depending on the polymer to particle concentration ratio (C-polymer/C-particle) and the hydrodynamic condition, different morphologies of streamers can be obtained. This is collated in the form of a state diagram. Surprisingly, it is observed that aged polymeric suspensions enhance streamer formation when employed in conjunction with gram flour powder that function as colloidal particles. Zeta potential and rheological measurements have been performed to gain further insights on the change in properties of polymer on account of ageing.