Biomedical Engineering Reference
In-Depth Information
+60
8
−
60
8
Outlet to N
2
O
sensor B
Outlet to N
2
O
sensor A
Colon analogue with leak hole
Positioned at
−
90
8
Sensing ring
Air inlet
Fig. 14
Sensing ring and colon analogue details showing the relative positions of the leak and the
sensing system inlets and outlets
5
Computer Simulation
For the computational analysis, Solid Works was used to generate a model of
the actual physical experiment. To detect a ppm increase over the time FloWorks
(included in Solid Works) was used. FloWorks uses conservation laws (Navier-
Stokes equations). To replicate the same conditions presented as used in the
experimental tests, the same conditions as used in the actual experiments were
used. Because pumps are not included in the software toolbox the pump used was
represented by a fan with a volume flow rate of 1 l/min. This fan will pump out the
same amount of gas that was used in the experimental arrange from the test box.
The box is filled with air at atmospheric pressure, 101,325 Pa, at a temperature of
293.2 K. The CAD model used for the computer simulations is shown in Fig.
15
.
Analyses were performed for three different sized holes (1, 2 and 3 mm) on the
pipe's top position for both physical and computational experiments as shown in
Figs.
13
and
14
respectively. An average of results from the physical experiments
for each size of hole was compared to its computer simulation and are shown in
the figures below. For all the computational experiments the injection of N
2
Ogas
started after 5 s.
