Abstract: The experimental investigation for turbulent separated flow in a 3-D 90°bend duct is reported.It is shown that,near the duct centre-lines,the turbulent flow can be ide-alized as local isotropy.The region between the separated bubble and the main region shows strong anisotropy.So the anisotropy of closure assumptions has to be taken into account in prediction methods.The Reynolds stress in the recirculation region is due to the turbulence structure,not the local mean velocity gradient.

Key words: separated flow, bend duct, hot- wireturbulent model