Tip leakage flow inside large tip clearances

Tip leakage flow inside the tip clearance for r/C = 3.45% is shown in fig. 3.15. Near the leading edge at X/Cx = 0.15, a separation bubble can be found near the pressure edge of the tip. Flow from the blade passage comes into the tip clearance from the suction side of blade and separates on the tip, as shown by the curved flow pattern near the suction side in the tip clearance (fig. 3.15(d)). At X/Cx = 0.45, a second much smaller separation bubble is formed near the suction edge of the tip, in addition to the separation bubble near the pressure edge on the tip surface as illustrated in fig. 3.15(h).

It is clear that the leakage flow inside the large tip clearance could be fairly complicated at large tip clearance levels. Near the leading edge, the leakage flow can comes from either the pressure side or the suction side. Around the middle tip surface, a double counter-rotating vortex is developed. From previous sections on the surface flow visualization, we can also observe the reverse flow and accumulation on the second half of tip surface.

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