Excess pressure drop and drag calculations for strain-hardening fluids with mild shear-thinning: Contraction and falling sphere problems

► Predicting pressure-drop for Boger fluid in 4:1:4 contraction-expansion flow. ► Relating the observed behaviour of highly-elastic Boger fluids in complex flows to their rheometrical behaviour. ► Models with first normal stress differences weaker than Oldroyd-B quadratic form, are capable of predicting enhanced excess pressure drop (epd). ► Investigating under what conditions enhanced drag results are obtained on the 2:1 falling sphere problem. ► Reduction observed in epd with the LPTT model in comparison with Oldroyd-B, is primarily attributed to shear-thinning effects.