*3.4. Cross Flow Velocity Distribution*

The flow near a blade's surface is three-dimensional, and the main flow should be along the derivative direction of the profiles mentioned above. If the cross-flow velocity *Wz* in the z-direction appears with a large value, it will interfere with the main flow greatly, and even large vortex fields and viscous loss form. Figure 11 shows the cross-flow velocity distributions of profiles near blade I under different flow rates. Compared with Figure 10, the amplitude of cross-flow velocity *Wz* was significantly smaller than the relative velocity *W*. The *Wz* of profiles on the suction side was generally negative, showing a tendency to flow to the back cover plate. The *Wz* of profiles on the pressure side was generally small and fluctuated near zero value. The amplitude of *Wz* on the suction side for Q = 7 m3/h and 20 m3/h was larger than that for Q = 13 m3/h. Under three flow rates, when *Wz* of profile lpI-2 is compared with *Wz* of profile lpI-0.5, and *Wz* of profile lsI-2 is compared with *Wz* of profile lsI-0.5, it can be found that the cross-flows were different.

**Figure 11.** Cross flow velocity distributions of profiles near blade I.
