▁in ▁order ▁to ▁pass ▁by ▁one ▁another . ▁ ▁F å hr æ us - L ind q v ist ▁effect ▁▁ ▁Robert ▁( Rob in ) ▁S anno ▁F å hr æ us , ▁a ▁Swedish ▁path ologist , ▁and ▁h emat ologist , ▁and ▁Johan ▁Tor sten ▁Lind q v ist , ▁a ▁Swedish ▁phys ician , ▁observed ▁that ▁when ▁blood ▁flows ▁through ▁vessels ▁smaller ▁than ▁about ▁ 1 . 5   ▁mm ▁in ▁diameter , ▁the ▁apparent ▁vis cos ity ▁of ▁the ▁fluid ▁decre ases . ▁The ▁vis cos ity ▁of ▁blood ▁decre ases ▁as ▁the ▁percent ▁of ▁the ▁diameter ▁of ▁a ▁vessel ▁occupied ▁by ▁the ▁cell - free ▁layer ▁increases . ▁However , ▁when ▁the ▁diameter ▁of ▁the ▁t ube ▁approaches ▁the ▁diameter ▁of ▁the ▁er yth ro cy te , ▁the ▁vis cos ity ▁increases ▁dram atically . ▁For ▁blood ▁flow ▁through ▁tub es ▁less ▁than ▁approximately ▁ 1   ▁mm ▁in ▁diameter , ▁the ▁vis cos ity ▁is ▁not ▁constant ▁with ▁respect ▁to ▁the ▁t ube ▁diameter . ▁Therefore , ▁blood ▁behav es ▁as ▁a ▁non - New ton ian ▁fluid ▁in ▁such ▁blood ▁vessels . ▁ ▁App lications ▁of ▁Bio fl uid ▁Dynam ics ▁▁ ▁Bio fl uid ▁Dynam ics ▁refers ▁to ▁the ▁study ▁of ▁fluid ▁Dynam ics ▁of ▁basic ▁bi ological ▁flu ids ▁such ▁as ▁blood , ▁air ▁etc . ▁and ▁has ▁immense ▁applications ▁in ▁the ▁field ▁of ▁diagn osing , ▁tre ating ▁and ▁certain ▁surg ical ▁procedures ▁related ▁to ▁the ▁dis orders / d