Effects of dilute low molecular weight poly(ethylene oxide) solutions in immiscible radial viscous fingering instabilities

We experimentally study the effects of normal stress differences in immiscible radial viscous fingering instability a Hele–Shaw cell. Dilute low molecular weight poly(ethylene oxide) (PEO) solutions are used as displaced fluid to focus on elastic without shear-thinning behavior. The PEO is varied investigate differences. experimental observations reveal that nonmonotonic and opposing evident depending stage evolution. Decreases reduce number fingers widen finger width early stage. However, increase promotes tip splitting narrows but suppresses intermediate Weissenberg numbers estimated at different stages instabilities. Tip occurs highest covered this suppression observed numbers. At numbers, we observe an increased reduced fingers.