▁heart ▁val ves . ▁St en otic ▁comes ▁from ▁the ▁Greek ▁word ▁" sten os ," ▁meaning ▁narrow . ▁St en otic ▁means ▁narrow ed , ▁and ▁a ▁st en otic ▁heart ▁val ve ▁is ▁one ▁in ▁which ▁the ▁narrow ing ▁of ▁the ▁val ve ▁is ▁a ▁result ▁of ▁the ▁pla que ▁formation ▁on ▁the ▁val ve . ▁ ▁The ▁W om ers ley ▁number , ▁or ▁alpha ▁parameter , ▁is ▁another ▁dimension less ▁parameter ▁like ▁the ▁Pr and tl ▁number ▁or ▁Reyn olds ▁number ▁that ▁has ▁been ▁used ▁in ▁the ▁study ▁of ▁fluid ▁dynamics . ▁This ▁parameter ▁represents ▁a ▁ratio ▁of ▁trans ient ▁to ▁vis c ous ▁forces , ▁just ▁as ▁the ▁Reyn olds ▁number ▁represented ▁a ▁ratio ▁of ▁in ert ial ▁to ▁vis c ous ▁forces . ▁A ▁characteristic ▁frequency ▁represents ▁the ▁time ▁dependence ▁of ▁the ▁parameter . ▁The ▁W om ers ley ▁number ▁may ▁be ▁written ▁as .: ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁ ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁ ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁ ▁▁▁▁▁▁▁▁▁▁ ▁Where ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁ ▁= ▁W om ers ely ▁Number ▁▁▁▁▁▁▁▁▁▁▁▁▁▁ ▁r ▁= ▁vessel ▁radius ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁ ▁= ▁fundamental ▁frequency ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁ ▁= ▁kin ematic ▁vis cos ity ▁= ▁▁ ▁The ▁flow ▁profile ▁becomes ▁bl unter ▁near ▁the ▁center line ▁of ▁the ▁vessel ▁in ▁high ▁frequency ▁flows , ▁ ▁because ▁the ▁in ert ia ▁forces ▁become ▁more ▁important ▁than ▁vis c ous ▁forces . ▁But ▁vis c ous ▁forces ▁are ▁still ▁important ▁near ▁the ▁wall ▁as ▁here ▁the ▁velocity ▁of ▁the ▁flow ▁is ▁almost ▁zero ▁due ▁to ▁the ▁effect ▁of ▁the ▁wall ▁and ▁the ▁no - s lip ▁condition . ▁Moreover ,