Encyclopaedia Britannica, 11th Edition, "Husband" to "Hydrolysis" / Volume 14, Slice 1

by Various

Coefficients of Discharge for Rectangular Orifices, Sharp-edged, in Vertical Plane Surfaces.

Head to Centre of Orifice.	Ratio of Height to Width.
	4	2	11⁄2	1	3⁄4	1⁄2	1⁄4	1⁄8
Feet.	4 ft. high. 1 ft. wide.	2 ft. high. 1 ft. wide.	11⁄2 ft. high. 1 ft. wide.	1 ft. high. 1 ft. wide.	0.75 ft. high. 1 ft. wide.	0.50 ft. high. 1 ft. wide.	0.25 ft. high. 1 ft. wide.	0.125 ft. high. 1 ft. wide.
0.2	..	..	..	..	..	..	..	.6333
.3	..	..	..	..	..	..	.6293	.6334
.4	..	..	..	..	..	.6140	.6306	.6334
.5	..	..	..	..	.6050	.6150	.6313	.6333
.6	..	..	..	.5984	.6063	.6156	.6317	.6332
.7	..	..	..	.5994	.6074	.6162	.6319	.6328
.8	..	..	.6130	.6000	.6082	.6165	.6322	.6326
.9	..	..	.6134	.6006	.6086	.6168	.6323	.6324
1.0	..	..	.6135	.6010	.6090	.6172	.6320	.6320
1.25	..	.6188	.6140	.6018	.6095	.6173	.6317	.6312
1.50	..	.6187	.6144	.6026	.6100	.6172	.6313	.6303
1.75	..	.6186	.6145	.6033	.6103	.6168	.6307	.6296
2	..	.6183	.6144	.6036	.6104	.6166	.6302	.6291
2.25	..	.6180	.6143	.6029	.6103	.6163	.6293	.6286
2.50	.6290	.6176	.6139	.6043	.6102	.6157	.6282	.6278
2.75	.6280	.6173	.6136	.6046	.6101	.6155	.6274	.6273
3	.6273	.6170	.6132	.6048	.6100	.6153	.6267	.6267
3.5	.6250	.6160	.6123	.6050	.6094	.6146	.6254	.6254
4	.6245	.6150	.6110	.6047	.6085	.6136	.6236	.6236
4.5	.6226	.6138	.6100	.6044	.6074	.6125	.6222	.6222
5	.6208	.6124	.6088	.6038	.6063	.6114	.6202	.6202
6	.6158	.6094	.6063	.6020	.6044	.6087	.6154	.6154
7	.6124	.6064	.6038	.6011	.6032	.6058	.6110	.6114
8	.6090	.6036	.6022	.6010	.6022	.6033	.6073	.6087
9	.6060	.6020	.6014	.6010	.6015	.6020	.6045	.6070
10	.6035	.6015	.6010	.6010	.6010	.6010	.6030	.6060
15	.6040	.6018	.6010	.6011	.6012	.6013	.6033	.6066
20	.6045	.6024	.6012	.6012	.6014	.6018	.6036	.6074
25	.6048	.6028	.6014	.6012	.6016	.6022	.6040	.6083
30	.6054	.6034	.6017	.6013	.6018	.6027	.6044	.6092
35	.6060	.6039	.6021	.6014	.6022	.6032	.6049	.6103
40	.6066	.6045	.6025	.6015	.6026	.6037	.6055	.6114
45	.6054	.6052	.6029	.6016	.6030	.6043	.6062	.6125
50	.6086	.6060	.6034	.6018	.6035	.6050	.6070	.6140

§ 21. Orifices with Edges of Sensible Thickness.—When the edges of the orifice are not bevelled outwards, but have a sensible thickness, the coefficient of discharge is somewhat altered. The following table gives values of the coefficient of discharge for the arrangements of the orifice shown in vertical section at P, Q, R (fig. 20). The plan of all the orifices is shown at S. The planks forming the orifice and sluice were each 2 in. thick, and the orifices were all 24 in. wide. The heads were measured immediately over the orifice. In this case,

Q = cb (H − h) √ { 2g(H + h)/2 }.

§ 22. Partially Suppressed Contraction.—Since the contraction of the jet is due to the convergence towards the orifice of the issuing streams, it will be diminished if for any portion of the edge of the orifice the convergence is prevented. Thus, if an internal rim or border is applied to part of the edge of the orifice (fig. 21), the convergence for so much of the edge is suppressed. For such cases G. Bidone found the following empirical formulae applicable:—

Table of Coefficients of Discharge for Rectangular Vertical Orifices in Fig. 20.

Head h above upper edge of Orifice in feet.	Height of Orifice, H − h, in feet.
	1.31			0.66			0.16			0.10
	P	Q	R	P	Q	R	P	Q	R	P	Q	R
0.328	0.598	0.644	0.648	0.634	0.665	0.668	0.691	0.664	0.666	0.710	0.694	0.696
.656	0.609	0.653	0.657	0.640	0.672	0.675	0.685	0.687	0.688	0.696	0.704	0.706
.787	0.612	0.655	0.659	0.641	0.674	0.677	0.684	0.690	0.692	0.694	0.706	0.708
.984	0.616	0.656	0.660	0.641	0.675	0.678	0.683	0.693	0.695	0.692	0.709	0.711
1.968	0.618	0.649	0.653	0.640	0.676	0.679	0.678	0.695	0.697	0.688	0.710	0.712
3.28	0.608	0.632	0.634	0.638	0.674	0.676	0.673	0.694	0.695	0.680	0.704	0.705
4.27	0.602	0.624	0.626	0.637	0.673	0.675	0.672	0.693	0.694	0.678	0.701	0.702
4.92	0.598	0.620	0.622	0.637	0.673	0.674	0.672	0.692	0.693	0.676	0.699	0.699
5.58	0.596	0.618	0.620	0.637	0.672	0.673	0.672	0.692	0.693	0.676	0.698	0.698
6.56	0.595	0.615	0.617	0.636	0.671	0.672	0.671	0.691	0.692	0.675	0.696	0.696
9.84	0.592	0.611	0.612	0.634	0.669	0.670	0.668	0.689	0.690	0.672	0.693	0.693

For rectangular orifices,

Cc = 0.62 (1 + 0.152 n/p);