Propeller Pressure Field in a Nonuniform Flow 



2. On the basis of the calculations made it is seen that the space-variable 

 wake increases the pulsating pressures on a ship hull surface generated by a 

 propeller. The magnitude of this increase depends upon the degree of nonuni- 

 formity of the inflow at the propeller location. The maximum pressure ampli- 

 tudes at some points of the hull surface can be 1.2 to 1.6 times greater than 

 those calculated under the uniform inflow assumption. The lower limit corre- 

 sponds to the case of moderately nonuniform flow behind the hull of a twin-screw 

 ship; the upper limit corresponds to the case of a significantly nonuniform wake 

 behind a single-screw ship. 



Calculations made by the authors confirm the conclusion of earlier work by 

 Breslin and his colleagues that the space -variable inflow velocities are of 

 greater relative importance as the distance from the propeller increases. 



3. For a given wake distribution over the screw disk the smaller the pro- 

 peller loading is, the more pronounced will be the pressure amplitude increase 

 due to nonuniformity. .... . .,.. 



4. When calculating the pressures generated by a propeller in nonuniform 

 flow one may use the quasi-steady values of circulation instead of nonstationary 

 ones. The error involved by this substitution will be within the range of accu- 

 racy of the method based on the lifting-line representation of the propeller. 



5. To calculate the pressures generated by a ship propeller in a nonuniform 

 flow with greater accuracy it would be necessary to develop the method of cal- 

 culation based on the nonstationary lifting-surface theory of propellers. 



REFERENCES 



1. Breslin, J. P., "Review and Extension of Theory for Near-Field Propeller- 

 Induced Vibratory Effects," Fourth Symposium on Naval Hydrodynamics, 

 Washington, 1962 i ••,-.> .i 



2. Breslin, J. P., "Review of Theoretical Predictions of Vibratory Pressures 

 and Forces Generated by Ship Propellers," Proceedings of the International 

 Ship Structure Congress, Vol. 4, Delft, 1964 



3. Babaev, N. N., and Lentjakov, V. G., "Some Aspects Concerning General 

 Ship Vibration," Sudpromgiz, 1961 -r , - • ; • 



4. Pohl, K. H., "Das instationare Druckfeld in der Umgebung eines Schiffspro- 

 pellers und die von ihm auf Benachbarten Platten erzeugten periodischen 

 Krafte," Schiffstechnik, Vol. 32, June 1959 



5. Basin, A. M. and Miniovich, I. Y., "Theory and Design of Ship Propellers," 

 Sudpromgiz, 1963 



6. Tsakonas, S., Breslin, J. P., and Jen. N., "Pressure Field Around a Marine 

 Propeller Operating in a Wake," J. Ship Research 6, No. 4, 1963 



13 



