Question

fluid mechanica

1.67 A new computer drive is proposed to have a disc, as shown in Fig. P1.67. The dise is to rotate at 10,000 rpm, and the reader head is to be positioned 0.0005 in. above the surface of the disc. Estimate the shearing force on the reader head as result of the air between the dise and the head Hair = 18 x 10-6 N.s/m2 1.0 in-2.5 cm. Munson Stationary reader head 0.2-in.dia. , 10,000 rpm + 2 in 10.0005 in Rotating disc FIGURE P1.67

Answer 1

Solution - (1.67) aliven as ! speed of the disc (N) = 10,000 Apm Distance between the reader and the disc (4) = 0.0005 in. Diameter of the reader (d) = 0.2 in. Effective ladius (2) = 2 in. we know that, 11 inch = 0.0254 mette velocity (u) = ADN D = 2XL = 2x2 = 4 in = 0.1016 m. No 10,000 ipm. u= 7DN = 7x0.1016x10000 = 3191.89 60 60 u= 53.19 = 53,2 mlec. Ius 53.2 msec. 7- © 60 seal ba () - Max *( 3 ) * Mair = 18x10-6 Ns/m2 A = (0.00508)2 = I x 2.58 No-G A = 2,03x10-5 m2 u= 33.2 misec 1-27xlo-smi

put all values in er. ② - . Mair * A x y 18x10-6 x 2.034107 x 53.2 1.27X1025 1943.93x10=4 1-27 F = 1.531 X10-3 N.