BEKNOULLI'S THEOREM 



77 



Where the flow changes from steady to unsteady between (1) and (2) 

 the term iH 2 will then include the kinetic energy due to motion in 

 directions perpendicular to the axis of the pipe. 



ART. 31. EXPERIMENTAL VERIFICATION OF BERNOULLI'S 

 THEOREM. 



The apparatus shown (Fig. 35) consists of a horizontal passage having 

 parallel vertical sides of plate glass, the first half forming a converging, 

 and the second half a diverging channel. The passage connects two 

 reservoirs, A and B, and pressure tubes are erected at frequent intervals. 



FIG. 35. 



Water is fed into the tank A, which is of large area compared with the 

 passage, and is led away by the overflow C. By suitable regulation of the 

 flow into A, and of the height of the overflow C, the velocity of flow 

 through the channel and the pressure at any point may be regulated as 

 required. Aniline dye may be introduced into the incoming stream of 

 water by means of the capillary tube T. 



At very low speeds the motion throughout the passage is steady, and 

 the curve joining the tops of the pressure columns is as shown in (a). 

 At any point to the right of the throat the pressure head will be less than 

 that at the corresponding point to the left, because of viscous resistance, 

 so that, since the velocity head is the same at the two points, the total head 

 is less on the right. 



As the velocity is increased, the first indication of unsteady motion is 



