Abstract: Through the preparatory experiment conjecture of the light spherical object suspended

above the im- pact water column，it is judged that the stable suspension condition is related to

the impact point position of the water column. After decomposing the impact point of water column

in the direction of velocity，it is known from the Coanda effect that there is interaction force in

the process of fluid flowing through the curved object surface. Therefore，the boundary

layer theory is used to analyze the force on the object，and then the expression of the transverse

force on the object is given. The similar“recovery force”is explained when the impact point of water column

slightly deviates from the equilibrium impact position. The self-consistency of the theory is

verified by the experimental results.

Key words: suspended water wheel, Coanda effect, boundary layer theory, moment balance