THROUGH PIPES OR PASSAGES HAVING DIVERGENT BOUNDARIES. 105 
Percentage Loss of Head. 
6 Experimental 7964 530 (tan oe 
; (mean). coe 2 
10° 17°6 18:0 17°8 
Was 29°5 a7 31:3 
20° 475 475 46°7 
257 69°5 64°8 64:2 
30° 90-0 85-0 83°5 
35° 1030 104:0 103°5 
| 
A comparison with circular taper pipes of the same initial and final areas and having 
the same values of @ shows, as indicated in the following table, that the rectangular 
pipe gives a ereater loss of head, except for values of 9 between 10° and 15° :— 
Percentage Loss of Head. 
0. Circular Pipe (mean). Rectangular Pipe (mean). 
10° 17-5 17-6 | 
20° 43°5 47°5 
30° mc 90-0 
40° 89:0 108-0 
If pipes of the same length and same ratio of enlargement are compared, however, 
the rectangular pipe, having a greater value of 6 than the circular pipe, is much 
less efficient except for such lengths as would make 6, in the rectangular pipe, 
approximately 11°. 
Experiments on rectangular pipes having an enlargement ratio of 9 to 1, and having 
9 respectively 40°, 60°, and 90°, showed corresponding losses of 115, 122°3, and 119 
per cent. This indicates a maximum loss when @ is approximately 70°, or when it has 
sensibly the same value as gives maximum loss in the corresponding circular pipe. 
§ 5. Pipes or Square Section wira Unirormiy Divercent Bounparigs. 
Two pipes, having a smaller section 1°329 inch square and a larger section 2°658 
inches square and with @ respectively 7°5° and 30° were examined, these completing 
the series examined in the preceding experiments. ‘The results of the whole set of 
experiments are plotted in fig. 3. The percentage loss is a minimum for a value of @ 
in the neighbourhocd of 6°, practically the same as for a circular pipe, and has a value 
of about 14°5 per cent. 
For larger values of 6 the loss in a square pipe is considerably greater—85 per cent. 
TRANS. ROY. SOC. EDIN., VOL. XLVIII. PART I. (NO. 5). 17 
