Page 176 - Mechanical Engineer's Data Handbook

FLUID MECHANICS 165

Drag coefficients for various bodies (continued)

Shape L
Re
- - A Arrangement
d Cd 104
Hollow hemisphere flow on 0.80 0.1 lrd’
convex face 4

Hollow hemisphere flow on 1.42 0.1 lrd2
-
concave face 4

(a) High-drag car > 0.55 50 -
(b) d-b

(b) Medium-drag car 0.45 50 -

(c) Low-drag car <0.30 50 -

4.7 Fluid machines

4.7. I Centrifugal pump Fluid enters the impeller axially at its centre of
rotation through its ‘eye’and is discharged from its rim
A centrifugal pump consists of an impeller with vanes in a spiralling motion having received energy from the
rotating in a suitably shaped casing which has an inlet rotating impeller. This results in an increase in both
at the centre and usually a spiral ‘volute’ terminating pressure and velocity. The kinetic energy is mostly
in an outlet branch of circular cross-section to suit a converted to pressure energy in the volute and a
vipe. tapered section of the discharge branch.