A marine propeller operating behind a vessel is exposed to a highly non-uniform and unsteady inflow. The hull, skeg, shaft and supporting structures modify the local wake field, while transient flow structures introduce additional variations in the instantaneous propeller inflow.
Coupled CFD and fluid–structure interaction are used to investigate how these hydrodynamic conditions translate into individual blade loads and elastic structural response.
The Vessel Wake
Before considering the rotating propeller, the nominal wake field provides a clear picture of the strongly non-uniform inflow encountered at the propeller plane.
The hull, skeg and shaft arrangement produce pronounced spatial variations across the propeller disc. A rotating blade therefore experiences continuously changing inflow conditions as it passes through different regions of the wake.
From Wake Field to Blade Loading
The non-uniform wake translates directly into time-dependent blade loading. In the sliding-mesh simulation, the actual propeller rotation is resolved and each blade successively passes through different regions of the vessel wake.
The resulting thrust histories show pronounced cyclic variations. Superimposed fluctuations reflect the transient character of the surrounding flow, so that successive blade passages are similar but not perfectly identical.
Successive Blade Passages
The relationship between successive blade passages becomes particularly visible when individual blades are compared. Similar loading characteristics reappear at different times as the blades pass through corresponding regions of the wake.
The signals are nevertheless not exact repetitions. The vessel wake itself evolves in time, adding transient variations to the periodic loading associated with propeller rotation.
Fluid–Structure Interaction
The transient hydrodynamic loads are coupled directly to a finite-volume solid model of the propeller within STAR-CCM+.
This allows the elastic response of the blades to be evaluated together with the surrounding flow solution. The resulting deformation pattern reflects the spatially varying hydrodynamic loading acting on the individual propeller blades.
From Vessel Wake to Structural Response
The analysis demonstrates how the complete vessel flow environment influences propeller operation. Rather than considering the propeller as an isolated component, the numerical model captures the interaction between vessel wake, rotating propeller and structural blade response.
The approach enables the assessment of wake–propeller interaction, transient blade loading, load fluctuations, elastic blade deformation and structural stresses under realistic vessel operating conditions.
Case Setup
| Parameter | Configuration |
| Scale | Full scale |
| Vessel speed | 10 kn |
| Propeller diameter | 2.9 m |
| Number of blades | 5 |
| Rotational speed | 121.5 rpm |
| Flow simulation | Transient CFD |
| Propeller modelling | MRF / Sliding Mesh |
| Structural coupling | One-way FSI |
| Structural model | Finite-volume solid |
| Propeller material | Nickel-Aluminium Bronze |