scholarly journals Method for the Calculation of the Underwater Effective Wake Field for Propeller Optimization

Water ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 165
Author(s):  
Li Jianing ◽  
Zhao Dagang ◽  
Wang Chao ◽  
Sun Shuai ◽  
Ye Liyu
Keyword(s):  
Velocity Field ◽  
Hydrodynamic Performance ◽  
Actual Situation ◽  
Surface Panel Method ◽  
Design And Optimization ◽  
Wake Field ◽  
Iterative Calculation ◽  
Experimental Values ◽  
Induced Velocity ◽  
Effective Wake

A quasi-steady prediction model of propeller hydrodynamic performance was established here using the surface panel method to determine the effective wake field of a propeller. The apparent wake field was accurately determined in advance by CFD (Computational Fluid Dynamics). The average of the induced velocity near the front of the propeller was determined by coupling the steady calculation and the unsteady forecast to render the induced velocity field more consistent with the actual situation when the propeller works in a non-uniform flow field. By superimposing the induced velocity near the front of the propeller with the apparent wake field, the effective wake field was able to be determined. Then the induced velocity field was calculated again to determine the new effective wake. An iterative calculation method was used until the hydrodynamic performance converged. The case described here shows that the effective wake obtained by this method can better predict the hydrodynamic performance of the propeller, and it can provide a basis for the design and optimization of the propeller. It was found that the results of the prediction were consistent with the experimental values.

scholarly journals Experimental Investigation of propeller Wake Velocity Field for the Major Factors Affecting Propeller Wake Wash

2018 ◽  
Author(s):  
Md. Asif Amin ◽  
Bruce Colbourne ◽  
Brian Veitch
Keyword(s):  
Velocity Field ◽  
Axial Velocity ◽  
Significant Component ◽  
Factors Affecting ◽  
Wake Field ◽  
Propeller Wake ◽  
Axial Velocity Distribution ◽  
The Mean ◽  
Major Factors ◽  
Effective Wake

The propeller jet from a ship has a significant component directed upwards towards the free surface of the water, which can be used for ice management. This paper describes a comprehensive laboratory experiment where the influences of operational factors affecting a propeller wake velocity field were investigated. The experiment was done on a steady wake field to investigate the characteristics of the axial velocity of the fluid in the wake and the corresponding variability downstream of the propeller. The axial velocities and the variability recorded were time-averaged. Propeller rotational speed was found to be the most significant factor, followed by propeller inclination. The experimental results also provide some idea about the change of the patterns of the mean axial velocity distribution against the factors considered for the test throughout the effective wake field, as well as the relationships to predict the axial velocity for known factors.

Design and Performance Investigation of the Energy Recovering Rudder Bulb-Turbine Device

2017 ◽  
Author(s):  
Chunhui Wang ◽  
Ankang Hu ◽  
Fenglei Han
Keyword(s):  
Hydrodynamic Performance ◽  
Container Ship ◽  
Surface Panel Method ◽  
Iterative Calculation ◽  
Line Theory ◽  
And Performance ◽  
Large Container ◽  
Lifting Line ◽  
Lifting Line Theory ◽  
Bulb Turbine

This study presents the performance investigation of a rudder bulb-turbine device (RBTD), which is designed to recover the rotational energy into torque to drive a generator inside the rudder. The blade of turbine is designed first by using lifting line theory, which is modified by lifting surface theory. The induced velocities between the forward propeller and turbine are obtained through the surface panel method (SPM). Hydrodynamic performance for the system is predicted by using SPM. An iterative calculation method is used until the hydrodynamic performance of the system converges. Through the design of turbine behind propeller of a large container ship, the influence of rotational speed of turbine on hydrodynamic performance of propeller-turbine system is observed. Then the size of rudder bulb is determined by calculating the influence of rudder bulb geometry on the hydrodynamic performance of the propeller-rudder system. Based on CFD technology, the hydrodynamic performance of the propeller-rudder system without/with RBTD is also simulated, and velocity distribution is observed. The results show that RBTD is successfully designed and as a ship energy saving device is feasible.

Propeller Loading-Induced Velocity Field by Means of Unsteady Lifting Surface Theory

1973 ◽  
Vol 17 (03) ◽  
pp. 129-139
Author(s):  
W. R. Jacobs ◽  
S. Tsakonas
Keyword(s):  
Velocity Field ◽  
High Speed ◽  
Pressure Field ◽  
Numerical Procedure ◽  
Nonuniform Flow ◽  
Surface Theory ◽  
Loading Function ◽  
Lifting Surface ◽  
Space Function ◽  
Induced Velocity

An analysis based on the lifting surface theory has been developed for evaluation of the vibratory velocity field induced by the loading of an operating propeller in both uniform and nonuniform inflow fields. The analysis demonstrates that in the case of nonuniform flow the velocity at any field point is made up of a large number of combinations of the frequency constituents of the loading function with those of the space function (propagation or influence function). A numerical procedure has been developed adaptable to a high-speed digital computer (CDC 6600), and the existing program, which evaluates the steady and unsteady propeller loadings, the resulting hydrodynamic forces and moments, and the pressure field, has been extended to include evaluation of the velocity field as well. This program should thus become a highly versatile and useful tool for the ship researcher or designer.

Comments on Jacobs and Tsakonas: “Propeller Loading-Induced Velocity Field by Means of Unsteady Lifting Surface Theory”

1982 ◽  
Vol 26 (04) ◽  
pp. 266-268
Author(s):  
Theodore R. Goodman
Keyword(s):  
Velocity Field ◽  
Velocity Potential ◽  
Fourier Component ◽  
Surface Theory ◽  
Lifting Surface ◽  
Induced Velocity ◽  
Total Velocity

In the cited paper (2) a formula is given for the lth Fourier component of the velocity potential of an N-bladed propeller [equations (9) and (10) of the paper], (2). The total velocity potential is then, of course, given by the sum of all the components.

Effects of vortex-induced velocity on the development of a synthetic jet issuing into a turbulent boundary layer

2019 ◽  
Vol 870 ◽  
pp. 651-679 ◽  
Author(s):  
Tim Berk ◽  
Bharathram Ganapathisubramani
Keyword(s):  
Velocity Field ◽  
Momentum Transfer ◽  
Momentum Flux ◽  
Cross Flow ◽  
Measured Data ◽  
Velocity Fields ◽  
Synthetic Jet ◽  
Vortical Structures ◽  
The Cross ◽  
Induced Velocity

A synthetic jet issuing into a cross-flow influences the local velocity of the cross-flow. At the jet exit the jet is oriented in the wall-normal direction while the cross-flow is oriented in the streamwise direction, leading to a momentum transfer between the jet and the cross-flow. Streamwise momentum transferred from the cross-flow to the jet accelerates the pulses created by the jet. This momentum transfer continuous up to some point downstream where these pulses have the same velocity as the surrounding flow and are no longer blocking the cross-flow. The momentum transfer from the cross-flow to the jet leads to a momentum deficit in the cross-flow far downstream of the viscous near field of the jet. In the literature this momentum-flux deficit is often attributed to viscous blockage or to up-wash of low-momentum fluid. The present paper proposes and quantifies a third source of momentum deficit: a velocity induced opposite to the cross-flow by the vortical structures created by the synthetic jet. These vortical structures are reconstructed from measured data and their induced velocity is calculated using the Biot–Savart law. The three-dimensional three-component induced velocity fields show great similarity to the measured velocity fields, suggesting that this induced velocity is the main contributor to the velocity field around the synthetic jet and viscous effects have only a small influence. The momentum-flux deficit induced by the vortical structures is compared to the measured momentum-flux deficit, showing that the main part of this deficit is caused by the induced velocity. Variations with Strouhal number (frequency of the jet) and velocity ratio (velocity of the jet) are observed and discussed. An inviscid-flow model is developed, which represents the downstream evolution of the jet in cross-flow. Using the measured data as an input, this model is able to predict the deformation, (wall-normal) evolution and qualitative velocity field of the jet. The present study presents evidence that the velocity induced by the vortical structures forming a synthetic jet plays an important role in the development of and the velocity field around the jet.

Two-Phase Flow Model Applied in the Oxidation Ditch

2013 ◽  
Vol 838-841 ◽  
pp. 1659-1662
Author(s):  
Lin Chen ◽  
Qian Feng
Keyword(s):  
Close Relation ◽  
Phase Model ◽  
Hydrodynamic Performance ◽  
Oxidation Ditch ◽  
Two Phase ◽  
Good Correspondence ◽  
Design And Optimization ◽  
Numerical Tools ◽  
Computational Fluid Dynamics Cfd

The unique hydraulic characteristics in oxidation ditch have a close relation with the quality of treated water, the design and optimization of the oxidation ditch. The experimentally validated numerical tools, based on computational fluid dynamics(CFD), were proposed. Sewage- sludge two-phase model and liquid-gas two-phase model of an oxidation ditch were built through CFD numerical method. Meanwhile, a velocity field measurement was enforced on the ditch by Acoustic Doppler Velocimeter(ADV). The simulated results and experimental data were in good correspondence, which verify the simulation methods are reasonable and the simulation results are acceptable. The combination of simulation and experimrntal measurement has profound influence on the hydraulic optimization of oxidation ditch. 3D simulation could be a good supplement for improving the hydrodynamic performance in oxidation ditch designs.

Challenges in Modeling the Unsteady Aerodynamics of Wind Turbines

2002 ◽  
Author(s):  
J. Gordon Leishman
Keyword(s):  
Velocity Field ◽  
Wind Turbines ◽  
Unsteady Aerodynamics ◽  
Dynamic Stall ◽  
Experimental Measurements ◽  
Fundamental Limits ◽  
Unsteady Aerodynamic ◽  
Modeling Techniques ◽  
Induced Velocity

Many of the aerodynamic phenomena contributing to the observed effects on wind turbines are now known, but the details of the flow are still poorly understood and are challenging to predict accurately, issues discussed herein include the modeling of the induced velocity field produced by the vortical wake behind the turbine, the various unsteady aerodynamic issues associated with the blade sections, and the intricacies of dynamic stall. Fundamental limits exist in the capabilities of all models, and misunderstandings or ambiguities can also arise in how these models should be properly applied. A challenge for analysts is to use complementary experimental measurements and modeling techniques to better understand the aerodynamic problems found on wind turbines, and to develop more rigorous models with wider ranges of application.

Studies About Design of Rear Stator of Ducted Propeller Using CFD

2019 ◽  
Author(s):  
Dakui Feng ◽  
Hang Zhang ◽  
Yue Sun ◽  
Qing Wang ◽  
Xiaofei Hu
Keyword(s):  
High Efficiency ◽  
Design Method ◽  
Hydrodynamic Performance ◽  
Thrust Coefficient ◽  
Wake Field ◽  
Ducted Propeller ◽  
Total Thrust ◽  
Unsteady Rans ◽  
Simulation Results ◽  
Volume Method

Abstract Ducted propeller designs are becoming more popular because of their high efficiency, resistance to cavitation and low radiated noise. In this paper, unsteady RANS simulations are carried out for the design of rear stators for ducted propeller to improve its hydrodynamic performance. The design of rear stator is carried out based on the wake field behind propellers. The two-dimensional airfoil modified from NACA4603 is studied to obtain the angle of attack that makes thrust on stators maximum. The analyses are performed at different angles of attack, using commercial computational fluid dynamics (CFD) solver STAR-CCM+ to solve URANS equations. URANS equations are discretized by finite volume method and solved by PISO algorithm. Simulations have been made using unstructured grid with mesh moving technique. The simulation results indicate that the total thrust coefficient and efficiency of modified ducted propeller have been improved by 7.32% and 5.72% respectively compared with the parent one. The simulation results show that the design method is reasonable and feasible.

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