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Resistance coefficients for thin-walled perforated sheet or grid of strips with sharp edged orifices (according to
Fried & Idelchik). 
Conditions:
Range of sheet length to hole diameter ratio, 0 < l/Dh < 0.015
Reynolds number, Re > 105
Where:
for is the area of one orifice.
The resistance coefficient is given by:
| Open
Area |
Resistance Coefficient |
|
Open Area |
Resistance
Coefficient |
| 0.01 |
28677.936 |
|
0.51 |
3.729 |
| 0.02 |
7055.112 |
|
0.52 |
3.478 |
| 0.03 |
3085.115 |
|
0.53 |
3.245 |
| 0.04 |
1707.168 |
|
0.54 |
3.027 |
| 0.05 |
1074.657 |
|
0.55 |
2.824 |
| 0.06 |
733.924 |
|
0.56 |
2.635 |
| 0.07 |
530.188 |
|
0.57 |
2.458 |
| 0.08 |
399.066 |
|
0.58 |
2.293 |
| 0.09 |
309.930 |
|
0.59 |
2.138 |
| 0.10 |
246.716 |
|
0.60 |
1.993 |
| 0.11 |
200.347 |
|
0.61 |
1.858 |
| 0.12 |
165.385 |
|
0.62 |
1.731 |
| 0.13 |
138.414 |
|
0.63 |
1.613 |
| 0.14 |
117.203 |
|
0.64 |
1.501 |
| 0.15 |
100.243 |
|
0.65 |
1.397 |
| 0.16 |
86.487 |
|
0.66 |
1.299 |
| 0.17 |
75.190 |
|
0.67 |
1.207 |
| 0.18 |
65.810 |
|
0.68 |
1.121 |
| 0.19 |
57.944 |
|
0.69 |
1.040 |
| 0.20 |
51.291 |
|
0.70 |
0.964 |
| 0.21 |
45.620 |
|
0.71 |
0.892 |
| 0.22 |
40.751 |
|
0.72 |
0.825 |
| 0.23 |
36.544 |
|
0.73 |
0.762 |
| 0.24 |
32.888 |
|
0.74 |
0.703 |
| 0.25 |
29.693 |
|
0.75 |
0.647 |
| 0.26 |
26.888 |
|
0.76 |
0.595 |
| 0.27 |
24.413 |
|
0.77 |
0.546 |
| 0.28 |
22.221 |
|
0.78 |
0.500 |
| 0.29 |
20.273 |
|
0.79 |
0.457 |
| 0.30 |
18.534 |
|
0.80 |
0.416 |
| 0.31 |
16.976 |
|
0.81 |
0.378 |
| 0.32 |
15.578 |
|
0.82 |
0.343 |
| 0.33 |
14.318 |
|
0.83 |
0.309 |
| 0.34 |
13.181 |
|
0.84 |
0.278 |
| 0.35 |
12.150 |
|
0.85 |
0.249 |
| 0.36 |
11.215 |
|
0.86 |
0.221 |
| 0.37 |
10.364 |
|
0.87 |
0.196 |
| 0.38 |
9.589 |
|
0.88 |
0.172 |
| 0.39 |
8.880 |
|
0.89 |
0.150 |
| 0.40 |
8.232 |
|
0.90 |
0.129 |
| 0.41 |
7.637 |
|
0.91 |
0.110 |
| 0.42 |
7.091 |
|
0.92 |
0.093 |
| 0.43 |
6.589 |
|
0.93 |
0.076 |
| 0.44 |
6.126 |
|
0.94 |
0.062 |
| 0.45 |
5.700 |
|
0.95 |
0.048 |
| 0.46 |
5.305 |
|
0.96 |
0.036 |
| 0.47 |
4.941 |
|
0.97 |
0.025 |
| 0.48 |
4.603 |
|
0.98 |
0.015 |
| 0.49 |
4.290 |
|
0.99 |
0.007 |
| 0.50 |
3.999 |
|
1.00 |
0.000 |
An enclosure vent is an example where these coefficients are applicable.
REFERENCE:
Fried & Idelchik, Flow Resistance: A Design Guide for Engineers; Hemisphere Publishing Corporation, 1989; Diagram 8.1
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