we 98is) 
XXVIII.—The Loss of Energy at Oblique Impact of Two Confined Streams of 
Water. By Professor A. H. Gibson, D.Sc., University College, Dundee. 
(With Five Diagrams. ) 
(MS. received June 26, 1912, Read December 2, 1912. Issued separately January 10, 1913.) 
CONTENTS. 
PAGE PAGE 
1. Introduction . : : : : 3 . 799 | 5. Loss at Impact of Two Converging Streams, 
2. Description of Apparatus—Fiction Loss . . 800 both of which are equally deflected . S09 
3. Loss at Elbows . : : . 801 | 6. Conclusions . : : ; ; 810 
4, Loss at Impact of Two Converging Streams, 
only One of which is deflected by Impact . 804 
1. LyTRODUCTION. 
When two jets or streams of water moving with equal or unequal velocities meet 
at an angle and combine to form one common stream, the impact is usually accompanied 
by loss of energy, which may be large if the velocities are high. If the jets are free 
(exposed to air on every side), the pressures are unaltered by impact, and the loss may 
be readily calculated in terms of the initial velocities and angle of inclination, by an 
application of the equations of energy and of momentum. Where the streams are 
confined before and after impavt—as, for example, where the streams outflowing from 
the impeller of a centrifugal pump impinge on the more slowly moving body of water 
in the volute, or where the two streams combine in the mixing chamber of a jet pump 
or injector,—both pressures and velocities are altered by the impact, and the available 
data are insufficient to enable the magnitude of the losses to be predetermined from 
@ priory reasoning. 
Where an attempt has been made to calculate such losses it has been usual to 
assume that the kinetic energy possessed by the impinging stream, in virtue of its motion 
normal to the primary, or undeflected, stream, is entirely dissipated by the shock of 
impact, and that, if 9 be the angle of incidence and if v, and v, be the velocities of the 
primary and impinging streams, the loss due to the parallel component (v, cos 6) of 
the velocity is given by (v, cos 6 —,)?+2g foot-lbs. per lb. of the impinging jet. The 
total loss per lb. of this jet is then 
(v, sin 0)? + @s COS 0-24) pt Ips — Ce ten seni COS 8 5 Ob Ibs. 
9 g 
This assumes that the loss accompanying admixture of two such streams at different 
TRANS. ROY. SOC. EDIN., VOL. XLVIII., PART IV. (NO. 28). , 115 © 
