Do Propellers Sing?

Tuesday, February 01, 2011
The graphic shows the chamfering that goes from a 0.5 or 0.4 radius to the tip of suction side

By Leonardo Montoya, Rice Propulsion, in the January edition of MarineNews

Yes, sometimes they sing: Some propellers in service produce a high-pitched noise, often referred to as “singing.” This sound typically is a clear harmonic tone much like a humming or a ringing wine glass.

More of an annoyance than anything harmful, the causes of singing are not completely understood. Many theories have been put forward to account for the phenomenon of singing, but it appears to be affected by critical factors for which the theories make no allowance.

For instance, in some cases when a twin-screw vessel has one propeller that sings, the noise is eliminated just by switching the position of the propellers, or by replacing the propeller with an identical spare. Also, the fewer blades the propeller has, the less cases of singing are observed.

Mitigation of Singing: the Anti-Singing Edge
The singing is a function of propeller diameter and RPMs, boat speed and trailing-edge size (thickness) and roundness. In most of the cases, not much can be done on diameter, RPMs or speed, but we can modify the edge geometry. This has been the strategy for all efforts to eliminate singing.

Most propeller professionals (and others) are familiar with the anti-singing edge, a chamfering of the trailing edge, typically on the suction side. The intent of this shape is to avoid the creation of curving flow eddies by cleanly separating the flow off of the blade.

However the adoption of unduly thin edges can result in erosion or fracture of the blade near the edges. It is advised that an anti-sing edge be considered as a last resort to minimize the singing of an existing propeller.

Maritime Reporter August 2014 Digital Edition
FREE Maritime Reporter Subscription
Latest Maritime News    rss feeds

Marine Propulsion

ClassNK Update Design Support Tool for EEDI Verification

Minimum propulsion power evaluation software extended to calculate added resistance in irregular waves Classification society ClassNK has released the latest

Maersk CEO Appointed to UN Advisory

Morten Engelstoft, CEO of Services and Other Shipping, said CO2 issues will be on his agenda as a newly appointed member of a UN High-level Advisory Group for Sustainable Transport.

MN 100: ZF Marine Propulsion Systems

15351 SW 29th St. Ste 300 Miramar, FL 33027 Telephone: 786 417 3496 E-mail: edward.schwarz@zf.com Website: www.zfmarinecc.com CEO/President: Wolfgang Schmid Number

 
 
Maritime Careers / Shipboard Positions Maritime Contracts Naval Architecture Navigation Offshore Oil Pipelines Salvage Ship Repair Ship Simulators Shipbuilding / Vessel Construction
rss | archive | history | articles | privacy | terms and conditions | contributors | top maritime news | about us | copyright | maritime magazines
maritime security news | shipbuilding news | maritime industry | shipping news | maritime reporting | workboats news | ship design | maritime business

Time taken: 0.1364 sec (7 req/sec)