Hydrodynamic loads and wake dynamics of ducted propeller in oblique flow conditions

2019 ◽  
Vol 15 (6) ◽  
pp. 645-660
Author(s):  
Jie Gong ◽  
Chun-yu Guo ◽  
Nhan Phan-Thien ◽  
Boo Cheong Khoo
Keyword(s):  
Flow Conditions ◽  
Hydrodynamic Loads ◽  
Oblique Flow ◽  
Ducted Propeller

scholarly journals Calculations of the Hydrodynamic Characteristics of a Ducted Propeller Operating in Oblique Flow

2017 ◽  
Vol 10 (20) ◽  
pp. 31
Author(s):  
Hassan Ghassemi ◽  
Sohrab Majdfar ◽  
Hamid Forouzan
Keyword(s):  
Stokes Equations ◽  
Open Water ◽  
Hydrodynamic Performance ◽  
Numerical Code ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Navier Stokes Equations ◽  
Oblique Flow ◽  
Ducted Propeller ◽  
Acceptable Agreement

The purpose of this paper is to calculate the hydrodynamic performance of a ducted propeller (hereafter Duct_P) at oblique flows. e numerical code based on the solution of the Reynolds-averaged Navier– Stokes equations (RANSE) applies to the Kaplan propeller with 19A duct. e shear-stress transport (SST)-k-ω turbulence model is used for the present results. Open-water hydrodynamic results are compared with experimental data showing a relatively acceptable agreement. Two oblique flow angles selected to analyze in this paper are 10 and 20 degrees. Numerical results of the pressure distribution and hydrodynamic performance are presented and discussed. 

Propeller wake evolution mechanisms in oblique flow conditions

2018 ◽  
Vol 845 ◽  
pp. 520-559 ◽  
Author(s):  
M. Felli ◽  
M. Falchi
Keyword(s):  
Operating Conditions ◽  
Wake Flow ◽  
Flow Conditions ◽  
Flow Measurements ◽  
Vortical Structures ◽  
Propeller Wake ◽  
Oblique Flow ◽  
Inclination Angles ◽  
Wake Instability ◽  
Underlying Mechanisms

In the present study the wake flow past an isolated propeller operating in oblique flow conditions is investigated experimentally. In particular, the investigation concerns a systematic topological comparison of the wake behaviour in axisymmetric and in oblique inflow conditions, for three inclination angles, and is focused on an analysis of the underlying mechanisms of wake evolution and instability. To this end, the experiment has been designed to investigate the dynamics of propeller vortical structures over a wide spatial extent covering the wake region from the propeller disk up to 4.5 diameters in the streamwise direction. Detailed flow measurements have been undertaken by particle image velocimetry (PIV), using a multicamera configuration with three cameras arranged side by side. This allowed simultaneous acquisition of a large flow extent at a spatial resolution adequate to resolve the smallest vortical structures involved in the process of propeller wake instability. The analysis has been based on both phase-locked averaged and instantaneous flow fields. The study extends the knowledge on the subject of propeller wake dynamics, highlighting the major hydrodynamic effects that non-axisymmetric propeller operating conditions exert on the mechanisms of wake evolution, instability and breakdown, such as asymmetric destabilization of the tip vortices on the leeward and windward sides of the wake, and the interference between the tip and the junction vortices, as well as the cause–effect relation between the breakdown of the blade trailing wake and the instability of the tip and hub vortices.

scholarly journals Computationally Efficient Force and Moment Models for Propellers in UAV Forward Flight Applications

Drones ◽  
2019 ◽  
Vol 3 (4) ◽  
pp. 77 ◽  
Author(s):  
Rajan Gill ◽  
Raffaello D’Andrea
Keyword(s):  
Taylor Series Expansion ◽  
Parametric Models ◽  
Lumped Parameter Model ◽  
Flow Conditions ◽  
Computationally Efficient ◽  
Forward Flight ◽  
Lumped Parameter ◽  
Oblique Flow ◽  
Moment Models ◽  
Thrust And Torque

Two low-order, parametric models are developed for the forces and moments that a rotating propeller undergoes in forward flight. The models are derived using a first-principles-based approach, and are computationally efficient in the sense of being represented by explicit expressions. The parameters for the models can be identified either using supervised learning/grey-box fitting from labelled data, or can be predicted using only the static load coefficients (i.e., the hover thrust and torque coefficients). The second model is a multinomial model that is derived by means of a Taylor series expansion of the first model, and can be viewed as a lower-order lumped parameter model. The models and parameter generation methods are experimentally tested against 19 propellers tested in a wind tunnel under oblique flow conditions, for which the data is made available. The models are tested against 181 additional propellers from existing datasets.

Hydrodynamic Performance of a FPSO in Highly Oblique Flow Conditions

2015 ◽  
Author(s):  
Mohammed Islam ◽  
Fatima Jahra ◽  
Ron Ryan ◽  
David Molyneux ◽  
Lee Hedd
Keyword(s):  
Cross Sections ◽  
Hydrodynamic Performance ◽  
Future Research ◽  
Flow Conditions ◽  
Local Flow ◽  
Hull Form ◽  
Flow Solver ◽  
Side Force ◽  
Oblique Flow ◽  
Yaw Moment

The capability of the viscous-flow solver Star-CCM+ to simulate the flow around a ship in steady oblique motion has been studied. To obtain insight into the reliability and accuracy of the results, grid dependency studies were conducted. Local flow quantities as well as integral variables were compared to measurement values. A FPSO hull form was considered for the simulations as well as experimental assessment of the resistance and flow field at multiple oblique flow conditions. The measurements and simulations have been completed at one draft, one Froude numbers and in 7 inflow conditions (0° to 180° with 30° increments). The measurements and predictions were made for the resistance in the inflow direction, side force and yawing moment. Additionally, the pressure and velocity distributions around the hull at multiple cross-sections are presented derived from the RANS predictions. Qualitatively, promising results are obtained. For practical purposes however, the accuracy of the results may require further improvement. For the current calculations, the predicted yaw moment is close to the measurements but the side force is under-predicted. Reasons for these discrepancies might be the neglect of trim and sinkage for the FPSO and of the insufficient grid resolution at the bow and stern. This should be studied in future research.

Velocities Induced by The Vortex Wake of a Propeller in a Duct

1963 ◽  
Vol 67 (635) ◽  
pp. 731-733
Author(s):  
Robert Hickling
Keyword(s):  
Radial Flow ◽  
Vortex Sheet ◽  
Flow Conditions ◽  
Propeller Blade ◽  
Vortex System ◽  
Vortex Sheets ◽  
Ducted Propeller ◽  
Lifting Line ◽  
Far Wake ◽  
Simple Flow

If it is assumed that the effect of radial flow can be neglected, then the vortices which are shed from the trailing edge of a propeller blade can be said to lie approximately on helical lines. These vortices form a vortex sheet which for practical purposes is assumed to extend unaltered downstream to infinity. If the propeller blade is approximated by a lifting-line of bound vorticity, then the velocities at the blade induced by the trailing vortex system can be derived from the simple flow conditions in the hypothetical far wake where the vortex sheets extend equally to infinity in both directions. Results are already well-known for the case where the vortex sheets exist in free space. It is the purpose here to examine the effect of adjacent boundaries, such as the hub and the duct wall of a ducted propeller. The results also relate to a test propeller in a tunnel.

scholarly journals Investigation on the Performance of a Ducted Propeller in Oblique Flow

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Qin Zhang ◽  
Rajeev K. Jaiman ◽  
Peifeng Ma ◽  
Jing Liu
Keyword(s):  
Open Water ◽  
Flow Dynamics ◽  
Navier Stokes ◽  
System A ◽  
Oblique Flow ◽  
Ducted Propeller ◽  
Blade Tip ◽  
Propeller Blades ◽  
Les Model ◽  
Thrust And Torque

In this study, the ducted propeller has been numerically investigated under oblique flow, which is crucial and challenging for the design and safe operation of the thruster driven vessel and dynamic positioning (DP) system. A Reynolds-averaged Navier–Stokes (RANS) model has been first evaluated in the quasi-steady investigation on a single ducted propeller operating in open water condition, and then a hybrid RANS/LES model is adapted for the transient sliding mesh computations. A representative test geometry considered here is a marine model thruster, which is discretized with structured hexahedral cells, and the gap between the blade tip and nozzle is carefully meshed to capture the flow dynamics. The computational results are assessed by a systematic grid convergence study and compared with the available experimental data. As a part of the novel contribution, multiple incidence angles from 15 deg to 60 deg have been analyzed with different advance coefficients. The main emphasis has been placed on the hydrodynamic loads that act on the propeller blades and nozzle as well as their variation with different configurations. The results reveal that while the nozzle absorbs much effort from the oblique flow, the imbalance between blades at different positions is still noticeable. Such unbalance flow dynamics on the blades, and the nozzle has a direct implication on the variation of thrust and torque of a marine thruster.

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