Schmiechen 



INFLOW OTHER THEN WITH THE FLUID 

 FL 



Fig. 2 - General conservation principal 



while the energy principle reads 



Ej - Ej < P , (9) 



due to the dissipation of mechanical energy in the system, the energy flows be- 

 ing defined as 



Ei = f J / [P(euin + Sot) -^C + t, ] dS, dt 



l/f Sj ^ ' 



^kinj ^pot> 3^"^ *c denoting the mass-specific kinetic and potential energies and 

 the diffusive energy transport, respectively. 



Further on only integral magnitudes will be dealt with and, as we are mainly 

 interested in the principles, the tensor notation will be dropped. 



3, DEFINITIONS OF EFFICIENCIES 



3.1 Propeller Efficiency 



From the basic concepts introduced, various performance parameters may 

 be derived, in particular if a reference length L and cross section A of the pro- 

 peller are introduced. The definitions of the advance number 



J = v/(fL) . (11) 



the thrust number 



Kp = T/(pf2L2A) , (12) 



and the power number 



Kp = P/(pi'L'A) , (13) 



according to the rules of dimensional analysis are very similar to those known 

 for screw propellers; Schmiechen, 1960. If one set of parameters is defined it 

 may be transformed into any other suitable set. 



1088 



