Page 37: of Maritime Reporter Magazine (May 15, 1977)

Alfred Conhagen

Issues New Catalog

Alfred Conhagen, Inc., a lead- ing supplier of pump, turbine and compressor parts, has issued a new brochure covering their capa- bilities and products.

For a copy of the brochure, write to M.A. Graziano, Alfred

Conhagen, Inc., 172 Lynhurst Av- enue, Staten Island, N.Y. 10305.

Principals shown above at the SNAME Chesapeake Section meeting are, left to right: P. Van Oossanen, author; Dr. William Morgan, moderator; Robert F. Roddy

Jr., author; Frank Sellars, Section chairman; Dr. Marinus Oosterveld, NSMB; Phillip

Eisenberg, past president of SNAME, and Dr. John P. Breslin, discusser.

Chesapeake Section Of SNAME Hears Papers

On Propeller Cavitation And Unsteady Forces design in a straightforward man- ner. In the paper, this was dem- onstrated by showing some re- sults of parametric studies.

An extensive discussion period followed the presentation of the paper. The discussers included

D. Burke, R. Cummings, B. Cox,

T. Brockett, and T. Huang of the

David Taylor Naval Ship Re- search Development Center, and

O. Scherer of Hydronautics.

The Chesapeake Section of The

Society of Naval Architects and

Marine Engineers held its fifth meeting of the 1976-77 season at the Officers Club of the Wash- ington Navy Yard in Washing- ton, D.C. The meeting included the presentation of two papers on unsteady propeller hydrody- namics.

The presentation of the papers followed a social hour and dinner attended by about 70 members.

The technical session was mod- erated by Dr. William Morgan of the David Taylor Naval Ship Re- search Development Center. The first paper, entitled "A New Pro- cedure for the Calculation of Un- steady Forces on a Marine Pro- peller," was presented by Robert

F. Roddy Jr. of DTNSRDC. The paper described a relatively straightforward calculation pro- cedure for the unsteady forces acting on a propeller operating in a nonuniform wake. The actual velocity distributions in the wake are used in the calculation of forces on the propeller blade at incremental positions around the propeller disk. Simplifications are made in the calculation of the in- stantaneous forces acting on the propeller blade. The author pre- sented comparisons with experi- mental data which showed agree- ment which was comparable with that obtained using other calcu- lation procedures. Dr. John Bres- lin of the Davidson Laboratory discussed the paper.

The second paper, entitled "Theoretical Prediction of Cavi- tation on Propellers," was pre- sented by P. Van Oossanen of the

Netherlands Ship Model Basin.

In this paper, a method was de- scribed for the assessment of cavitation inception and for the calculation of the type and extent of cavitation on marine propellers.

The adopted theory is suitable for application to nonuniform flows such as exist behind ships. Some primary effects associated with viscosity are also included, in par- ticular the problem of Reynolds number scaling such as occurs when testing models in cavitation test facilities at speeds lower than at full-scale.

It was shown that the described theory leads to reasonable corre- lations with actual cavitation pat- terns for lightly—and moderately —loaded propellers. For heavily loaded propellers, such as those of tankers, tugs, etc., the calcu- lated results were less satisfac- tory. The argument was made that this is due to the lack of knowledge regarding the change in the wake flow into the propel- ler due to the propeller load.

For minimizing the occurrence of cavitation in subcavitating pro- peller design, a long-standing ex- perience in both the design and testing of propellers in cavitation test facilities is normally required.

With the use of the described theory, however, it is possible, by systematically varying design pa- rameters, to arrive at a successful

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May 15, 19 77 45