| Summary: | 碩士 === 逢甲大學 === 機械工程學所 === 92 === The lift force and drag force of the sphere impinged by an inclined water jet were experimentally studied in this paper. Experiments show that the inclined water jet throws a ping-pong ball can make it spins and suspends in the air under the specific conditions, which specify the Reynolds numbers are ranged from 4500 to 6500 and the inclined angles of the water jet are ranged from 3.43 degree to 11.3 degree.
Results reveal that the inclined angle and the exit velocity of the water jet are two important factors to affect the rotation of the sphere which was impinged by an inclined water jet. Fixed the inclined angle of the water jet, the flow structure for the low exit velocity of the water jet is more organized than the flow structure for the high exit velocity of the water jet, the water strikes to the sphere with a higher velocity for the low exit velocity water jet, it ends up to rotate the sphere quickly.
On the other hand, fixed the exit velocity of the water jet, the angular speed of the sphere is increasing with the inclined angles, the sphere spins slowly for the water jet with small inclined angle and the sphere spins quickly for the water jet with large inclined angle. Results indicate that the drag coefficient decreases with the inclined angle of the water jet, it interesting to note out that the drag force on the fast spinning sphere reduced drastically because some of water was pulled out from the wake region. The lift coefficient increase proportionally with the inclined angle of the water jet, it evidently proves the Magnus effect of a rotating sphere.
|
|---|
