Stable core-annular flows of viscoelastic fluids using the visco-plastic lubrication technique

► Stable core-annular flows with viscoelastic core fluid and yield stress lubricating fluid. ► Carbopol and PEO. ► Yield stress preserves ring of unyielded material around interface, restricting instabilities. ► Secondary flows with elastic instability frozen into the yield stress fluid at interface. ► Flow stabilisation with entry flow contraction.