Biomedical Engineering Reference
In-Depth Information
compared for different designs of rotor to determine the optimum design of the
rotor.
2.
A
NALYSIS OF
F
LUID
F
LOW
2.1. Assumptions
The following assumptions were considered for the numerical solution of
high-speed spindles (HSS) using computational fluid dynamics (CFD):
HSS rotor rotational speed depends on the pressure of the compressed
air entering from the compressor. The numerical simulation was
carried out by a considering de-coupled system, i.e., for a given inlet
pressure (60 psi), the rotating speed of the rotor was assumed as a
constant value such as half-million rpm, i.e., the current study deals
only with the fluid problem, not the fluid/structure problem;
Steady-state simulation was assumed for all numerical simulations.
2.2. CFD Geometry Model
The bearing component of the HSS was omitted in the CFD model. The
outer diameter of the rotor is 0.3 inches (7.6 mm), inner diameter of the rotor
is 0.092 inches (2.34 mm), the height along the z-direction is 0.1445 inches
(3.6 mm) and the angle between the rotor blades is 90 degrees. A cylindrical
housing with a diameter of 0.31 inches (7.8 mm) was modeled around the
rotor with a height of 0.1735 inches (4.4 mm) so that the rotor could rotate
freely inside the housing. The spindle is driven by compressed air. Three
inlets, with a diameter of 0.055 inches (1.4 mm), that make an angle of 120
degrees with each other, were created around the housing. The inlets were
created at an angle of 45 degrees. An outlet for the air was created at the center
of the housing.
2.3. Fluid Model
The air was considered as an ideal gas. The flow in HSS is turbulent. The
turbulence is described by k-ε turbulent model, in which k is the turbulence
