Waterjet Propulsion 



In the optimization process two methods may be used, for we can either (see 

 Table Al): 



(i) choose a value of the inlet area and so accept an established amount 

 of external losses, thereby minimizing the sum of E + u + I; or 



(ii) choose a value of the inlet velocity ratio and so accept an estab- 

 lished amount of internal losses. In this case we minimize the 

 sum of E + u + P. 



Table Al 

 Optimization Procedures 



E = residual jet energy 



I = energy due to the internal losses in suction duct 

 U = energy due to the internal losses in discharge duct 

 p = energy due to the parasitic drag 



Total thrust method 



Basic thrust method 



A - constant 

 /3. = variable 



P~ = constant 



T 



/3 



/O A , Vq' ( r - X 1 ) 



The sum E + u + I is minimized 



/3j = constant i^ = constant 

 A^ = variable 



The sum E + u + P is minized 



How the value of the optimum velocity ratio may be found 



(a) Prefixed displacement 



Minimum Power directly 



Maximum Payload directly 



Maximum Range iterative process 



Fuel Economy iterative process 



(b) No prefixed displacement 



Minimum Power iterative process 



Maximum Payload iterative process 



Maximum Range iterative process 



Fuel Economy iterative process 



(a) Prefixed displacement 



Minimum Power directly 



Maximum Payload directly 



Maximum Range directly 



Fuel Economy directly 



(b) No prefixed displacement 



Minimum Power directly 



Maximum Payload directly 



Maximum Range iterative process 



Fuel Economy iterative process 



The optimization procedures can be carried out with different objectives in 

 mind, that is, either the minimum power, the maximum payload with a fixed 

 range, the maximum range with a fixed payload, or the best utilization of fuel 

 per mile. 



1057 



