﻿Instability of Gaseous Jets. 



373 



made a number of determinations of volumetric rates of flow, 

 through the gas-meter. In Table III. are given the dia- 

 meters, flaring-pressures, and volumetric rates of flow ; the 



Table III. 



Diam. of 

 Orifice in mm. 



Flaring Press, 

 in cm. water. 



Amount passed 

 per sec. when 



flaring, in 

 cubic inches. 



Linear Velocity 



of Flow 



X Constant. 



0-619 



31-0 



1152 



3006 



0643 



37-6 



1-271 



3073 



1-100 



37-0 



3-756 



3103 



1-107 



35-4 



3-526 



2914 



1-30 



13-4 



2-879 



1704 



2-00 



98 



5-759 



1440 



3-00 



5-8 



10-06 



1129 



quantity in the last column, called linear velocity, is obtained 

 by dividing the volumetric rate of flow by the square of the 

 diameter of the orifice. 



It is seen that the numbers in the last column show the 

 same sudden drop as the flaring-pressures in Table I. 



We have also made observations on the relation between 

 pressure and rate of flow, with a given orifice, for ignited 

 and unignited jets, and have found in every case that the 

 rate of flow for a given pressure is greater for an unignited 

 than for an ignited jet. " When a flame is lighted at the 

 burner there are further complications, of which it is difficult 

 to give an adequate explanation. The high temperature 

 leads indeed to increased viscosity, and this tends to explain 

 the higher pressures then admissible, and the graver notes 

 which then become operative. But it is probable that the 

 change due to ignition is of a still more fundamental 

 nature"*. 



The figure shows how the curve for the ignited jet lies 

 below that for the unignited jet. P is the pressure in cm. 

 of water and V is the volumetric rate of flow in cubic feel 

 per second. 



Rayleigh, 'Sound,' vol. ii. p. 409. 



