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142 4 Optical Rotor
1,800
1,600
Rotation rate (rpm) 1,200
1,400
1,000
800
600
400
200
0
0 50 100 150 200 250 300
Laser power (mW)
Fig. 4.30. Shuttlecock rotor rotation rate dependence on a laser power

(a) (b)
A B

Rotation h = 10 mm

h = 4 mm

h = 0 mm

Fig. 4.31. Velocity vectors in the plane 0.5 µm before the center plane for the rotor
of a =45 , 2r =3 µmand h =10 µm(a), and streamlines around the rotor (b)
◦

(h =4 µm), and slightly inward at the bottom (h =0 µm). Arrows show the
startingpoint of the flow.

Pressure and Shearing Stress

Figure 4.32 shows pressure P (a), and shearingstress S (b), on the surface
of the rotor. A high pressure (1.24 pN µm −2 ) arises on the upper edge of the
slope where the fluid velocity is high.
Flow-in occurs near the side wall due to the negative pressure. The pressure
on the flat end is very low due to the tangential direction of the rotation axis.
On the other hand, the shearing stresses are large at the top of the edge
(2.24 pN µm −2 ). The shearingstress on the side surface is small, which leads
to a low fluid flow alongthe side surface.