242 



T^ 



EFFECT OF CAVITATION ON PRESSURE 

 The action of an exponen- 

 tial wave upon a plate is illus- 

 trated in Figures 10 and n, which 

 are drawn to represent very rough- 

 ly the action of the shock wave 

 from 300 pounds of TNT upon a plate 

 of steel 1 inch thick, or from 1 

 ounce of TNT upon a plate ^ /^'J inch 

 thick. 



Figure 10 shows the ex- 

 cess pressure on the plate itself, 

 above hydrostatic pressure, plotted 



^ 5000 



S 4000 



3000 



2000 



1000 



-1000 







2 



1.6 



04 06 08 10 1,2 

 Time in milliseconds 



Figure 10 - Pressure on a Plate, in the 



Absence of Cavitation, plotted 



on a Time Base 



14 



13 



12 



10 9 8 7 6 5 4 



Distance from Plote in feet 



4000 



3000 



2000 



000 





 -1000 



2000 



Figure 11 - Distributions of Pressure behind a Plate at Successive 

 Instants of Time, in the Absence of Cavitation 



The incident mave approaches from the left, hence distance from the plate is plotted in that direction. 



on a basis of time. The time scale is labeled to correspond to 300 pounds of 

 TNT; for 1 ounce the times would be l/l7 as great. One curve shows the inci- 

 dent pressure, or the pressure that would exist in the water at the location 

 of the plate if the plate were absent, as given by Equation [12]. The other 

 curve shows the actual pressure on the plate, as given by Equation [1^]. 

 This may be thought of as made up of the incident pressure p together with a 

 component of pressure p" due to a reflected wave that travels back into the 

 water. 



