Prediction of high-amplitude forces during propeller crashback

Peter A. Chang, Michael P. Ebert, Jeremy Shipman, Krishnan Mahesh

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Scopus citations

Abstract

Propeller crashback, an emergency maneuver undertaken when a forward-moving vessel needs to stop quickly, involves reversing the propeller rotation and running the propeller in reverse into the oncoming flow. This maneuver generates low frequency, high amplitude forces on the blades which impart pitch and yaw moments on the vessel. The origins of these forces are uncertain and there are no tools based on first principles with which propeller designers can predict the maximum loadings during crashback. In order to better understand the origins of these phenomena and develop a loading prediction tool a large eddy simulation (LES) methodology using an unstructured, finite volume, incompressible LES code with a 2 nd-order accurate central difference (CD) flux reconstruction methodology, and a dynamic sub-grid scale model is being applied to crashback. In this paper, we compare results of this code with experimental data and a commercially-available unstructured finite volume LES code with upwind (UW) flux reconstruction without sub-grid scale model. Crashback simulations have been performed on the 0.3048 m diameter, zero-skew angle, 5-bladed Propeller 4381 operating at J=-0.5. We compare the mean, RMS higher order statistical moments for the integrated forces and moments to experimental data. Comparison to the experimental power spectral density (PSD) functions shows that both codes correctly predict the low-frequency blade loading and the blade rate energy concentrations. However, the CD code predicts a wider range of turbulence scales around the blade rate peak that may be important for loading dynamics. The CD LES data reveals that the flow has a bi-modal behavior that switches between vortex ring (VR) and axial jet (AJ) modes which are associated with minimum and maximum loadings, respectively.

Original languageEnglish (US)
Title of host publication2008 Proceedings of the Department of Defense High Performance Computing Modernization Program
Subtitle of host publicationUsers Group Conference - Solving the Hard Problems
Pages74-82
Number of pages9
DOIs
StatePublished - Dec 1 2008
Event2008 Department of Defense High Performance Computing Modernization Program: Users Group Conference - Solving the Hard Problems - Seattle, WA, United States
Duration: Jul 14 2007Jul 17 2007

Publication series

Name2008 Proceedings of the Department of Defense High Performance Computing Modernization Program: Users Group Conference - Solving the Hard Problems

Other

Other2008 Department of Defense High Performance Computing Modernization Program: Users Group Conference - Solving the Hard Problems
CountryUnited States
CitySeattle, WA
Period7/14/077/17/07

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