Response of Propulsors to Turbulence 



In the case of the 4- inch- grid the theory predicts an rms thrust coefficient 

 of 0.0234, which is equal to 12.8% of the steady-state thrust coefficient. In the 

 case of the 6-inch grid the corresponding values are 0.0250 and 13.6%. In view 

 of the good agreement of the power spectral density at low frequencies, these 

 values appear to be reliable. 



REFERENCES 



1. Kemp, N.H., and Sears, W.R., "Aerodynamic Interference Between Moving 

 Blade Rows," J. Aeronautical Sciences 20, 585-598 (1953) 



2. Kemp, N.H., and Sears, W.R., "The Unsteady Forces Due to Viscous Wakes 

 in Turbomachines," J. Aeronautical Sciences 22, 478-483 (1955) 



3. Lewis, F.M., and Tachmindji, A.J. , "Propeller Forces Exciting Hull Vibra- 

 tion," Trans. SNAME 62, 1954 



4. Shioiri, J. and Tsakonas, S., "Three-Dimensional Approach to the Gust 

 Problem for a Screw Propeller," Stevens Institute of Technology, Davidson 

 Laboratory Report 940, Mar. 1963 



5. Boswell, R., "Measurement, Correlation with Theory, and Parametric In- 

 vestigation of Unsteady Propeller Forces and Moments," M.S. Thesis, De- 

 partment of Aerospace Engineering, The Pennsylvania State University, 

 Dec. 1967 



6. Stewart, R.W., and Townsend, A.A., "Similarity and Self- Preservation in 

 Isotropic Turbulence," Trans. Royal Soc. 243, 359-386 (1951) 



7. Sears, W.R., "Some Aspects of Non- Stationary Air Foil Theory and Its 

 Practical Application," J. Aeronautical Sciences 8(No. 3) (Jan. 1941) 



8. Lehman, A.F., "Garfield Thomas Water Tunnel," Ordnance Research Lab- 

 oratory Report NOrd 16597-56, The Pennsylvania State University, Sept. 

 1959 



DISCUSSION 



Paul Kaplan 



Oceanics, Inc. 



Technical Industrial Park, New York 



This paper presents an aspect of unsteady propeller forces that differs from 

 those discussed earlier: it covers a stochastic influence rather than a regular 



311 



