810 PROF. A. H. GIBSON ON THE LOSS OF ENERGY AT OBLIQUE IMPACT 
as each of the single streams, and having a direction making an angle : with each of 
the latter. 
Under these conditions the loss per lb. of each of the impinging streams might be 
expected to be approximately the same as that experienced in an elbow having uniform 
area throughout with a deviation equal to S 
The pipes examined had values of 6 respectively, equal to 15°, 30°, and 60°, and 
cross-sectional areas $ inch x 1 inch, and within the limits of experimental error the 
above conclusion was found to be justified. 
6. CONCLUSIONS. 
The following are the conclusions to be drawn from the experimental results of the 
investigation :— 
(w) The friction loss per foot run of such rectangular passages as were used, — 
with sections varying from 1 inch x $ inch to 24 inches x 4 inch, is 
given by 
00360" 
~~ Yom'™ 
_ 0000560" 
nyo 
h feet 
feet, 
where m = area~+ perimeter in foot-units. 
2 
(b) The loss at plain elbows of uniform rectangular section is given by tS feet, 
where F = 00006760". Here @ is the angle of deviation of the elbow 
in degrees. 
(c) Where the elbow is formed by the junction of one pipe with a second, and — 
so has a dead end facing the final direction of flow, the loss is increased. 
In such a case 
z m—1\? , :00046,,. 
¥= 4( —*) + m7 a 
where m is the ratio of the areas of the outlet and inlet legs of the elbow. 
(d) The loss at impact of two confined streams, only one of which suffers 
deviation, is given by 
Fi aces 
loss = ant oy foot-lbs. per lb. of the impinging jet (2). 
By the impinging jet is meant that which is deviated on impact. The — 
velocity of this stream is v, and that of the primary or undeviated stream 
is 1, The values of the coefficients a and b in this formula are given in — 
Tables II. and I., and by the curves of figs. 4 and 5. — 
