* Flexible membrane thickness
* External fluid velocity
Internal pressure causes the pretension forces in the flexible membrane tubes. The
pretension forces are also based on the area of the tube opening and so are functions of
the tube diameter. Drag on a given member is a direct function of tube length and tube
diameter. Drag is also a function of the flowing fluid velocity squared. Three of the five
independent variables are combined using data from commercially available materials.
Table 5.1 presents Vinyl-Flow data including tube diameter, thickness, and working
pressure for a given series number. Simulation results make convenient the grouping of
VF-Series' by pressure to show approximately constant pressure trends. The three
pressure range groups are indicated in Table 5.1. The following simulations vary Vinyl-
Flow series number, tube length, and external fluid velocity to determine effects on cage
performance.
Table 5.1 Manufacturer data for Vinyl-Flow commercial drainage tubing
Nominal Hose Approximate Working Coil Approx. Pressure
Series Size ID Wall Thickness Pressure Length Weight Group
No. (in.) (in.) (in.) (psi) (ft.) (lbs.lcoil) (psi)
VF 150 111, 1.673 .0669 80 300 48
VF 200 2 2.165 .0669 80 300 69 70-80
VF 250 2'/ 2.598 .0787 80 300 87
VF 300 3 3.130 .0787 70 300 117
VF 400 4 4.134 .0827 70 300 156
VF 500 5 5.039 .0866 40 300 204
VF 600 6 6.181 .0866 50 300 258 40-50
VF 800 8 8.169 .1063 45 100/300 130/390
VF1000 10 10.118 .1181 35 100 181
VF1200 12 12.126 .1181 30 100 195 30-35
VF1400 14 14.134 .1181 30 100 262
VF1600 16 16.142 .1181 30 100 310
5.2 Failure Criteria
The failure criteria for both flow cases are the points when wrinkling occurs
anywhere in the fabric tubing and when stress exceeds the ultimate strength of the