The /u/ vowel is usually spelled <oo>, <ew>, <u>, <ui> in bruise and <o> in who. The /aʊ/ diphthong is spelled <owCe> or <ou>. Notice the homograph wound.
This is a contrast between a long vowel and a diphthong, fairly well separated in starting position and distinguished by lip-rounding. It is not a problem for any learners.
The density figure is 2.49%. The set makes 61 semantic contrasts giving a loading of 51.7%.
allude allowed blues blouse boo bough boos boughs boo bow booing bowing booed bowed boos bows boot bout boots bouts booze boughs booze bows brew brow brews brows brewed browed bruise brows bruise browse bruised browsed bruises browses bruising browsing chew chow chews chows chute shout chutes shouts clewed cloud clued cloud coo cow cooed cowed cooing cowing coos cows cool cowl cooling cowling cools cowls crewed crowd croon crown crooned crowned crooning crowning croons crowns crude crowd do dhow do's dhows doer dower doers dowers flute flout fluted flouted flutes flouts fluting flouting fool foul fooled fouled fooling fouling fools fouls gnu now goon gown goons gowns Hoo how hula howler hulas howlers jewel jowl jewels jowls joule jowl joules jowls Julie jowly loose louse loot lout loots louts moo mow mooing mowing moos mows mooned mound moose mouse mooses mouses noon noun noose nous Pru prow prude proud rood rowed root rout rooted routed rooting routing roots routs Rudy rowdy rue row rued rowed rues rows ruing rowing rues rouse ruse rouse ruses rouses ruse rows school scowl schooled scowled schooling scowling schools scowls scoot scout scooted scouted scooting scouting scoots scouts shoot shout shooting shouting shoots shouts shrewd shroud slew slough slews sloughs sooth south sou sow sous sows strewed Stroud toot tout tooted touted tooting touting toots touts whoever however who'll howl who's house woo wow woos wows wound wound you'll yowl
Credit: John Higgins