Measurement of suction holes' discharge coefficients Cd in an internal passage with rib turbulators and suction holes are presented.The internal passage is a rectangular channel with two opposite ribbed walls

the aspect ratio is 0.5

and the rib turbulators are arranged in a staggered way on the two wider walls.The cylindrical suction holes are 45° inclined and perpendicularly oriented

they are placed on one ribbed wall.Tests were run by varying rib tubulators' angles as 45°

60°

90° and 120°

with Reynolds numbers Re changing from 40000 to 80000 and suction ratios (SR) changing from 0.30 to 0.60.Influences of rib tuburlators angles

Reynolds number and suction ratio on Cdare studied. Results indicate:(1) Cdincreases a little along the internal passage;(2) increasing rib turbulator's angle leads to higher Cd

and the maximum Cdis obtained when the rib angle is 120°;(3) varying suction ratio contributes no remarkable effect on changing discharge coefficients;(4) Reynolds number also has no obvious influence on discharge coefficients.