scholarly journals Numerical Analysis of Hub Effect on Hydrodynamic Performance of Propellers with Inclusion of PBCF to Equalize the Induced Velocity

2012 ◽  
Vol 19 (2) ◽  
pp. 17-24 ◽  
Author(s):  
Hassan Ghassemi ◽  
Amin Mardan ◽  
Abdollah Ardeshir
Keyword(s):  
Numerical Analysis ◽  
Velocity Potential ◽  
Boundary Integral ◽  
The Body ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Body Effect ◽  
Quadrilateral Elements ◽  
Induced Velocity ◽  
Hub Effect

Numerical Analysis of Hub Effect on Hydrodynamic Performance of Propellers with Inclusion of PBCF to Equalize the Induced Velocity In this article the boundary element method (BEM) is applied to analyze the propeller hub as a non-lifting body and the blades in its vicinity as lifting bodies. In solver, the geometrical modeling of hub, blades are PBCF (Propeller Boss Cap Fin) constructed by quadrilateral elements. The velocity potential is determined on each element by discretized boundary integral equation. Iterative procedure is used to consider the adjacent body effect. In each step the body was independently analyzed with the influence of near body considered in inflow velocity. The induced velocity of propeller was calculated with and without PBCF in downstream. PBCF, an energy-saving device, reduces and uniforms the induced velocity of propeller in downstream. Numerical results of propeller hydrodynamic characteristics including hub effect, induced velocities, PBCF influence are presented.

Numerical Analysis of the Fluid Flow Behavior in the Plain Journal Bearing at Textured and Not Textured Surface

2021 ◽  
Vol 9 (1) ◽  
pp. 40-59
Author(s):  
Bendaoud Nadia ◽  
Mehala Kadda
Keyword(s):  
Fluid Flow ◽  
Numerical Analysis ◽  
Flow Behavior ◽  
Rotational Velocity ◽  
Operating Conditions ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Textured Surface ◽  
Plain Bearing ◽  
Rotating Machines

Hydrodynamic plain bearings are components that provide the guiding in rotation of rotating machines, such as turbines, the reactors. This equipment works under very severe operating conditions. In order to improve the hydrodynamic performance of these rotating machines, the industrialists specialized in the manufacture of hydrodynamic bearings have designed a bearing model with its textured interior surface. The numerical analysis is carried out to study the for both plain bearings types with a textured a non-textured surface thus to see the improvement of the plain bearing hydrodynamic performances, as well as the fluid flow behavior in motion. The analysis is performed by solving the continuity equation of Navier-Stokes, by the finite volume method, using CFD code. The numerical results show that the most important hydrodynamic characteristics such as pressure, minimal film thickness, friction torque, leakage flow, are significant for the textured plain bearing under rotational velocity of 6000rpm and radial load 10000N compared to obtained for a non-textured plain bearing.

scholarly journals Theoretical modeling of hydrodynamic characteristics of a compound column-plate structure based on a novel derivation of mean drift force formulation

2018 ◽  
Vol 233 (4) ◽  
pp. 1022-1036 ◽  
Author(s):  
Peiwen Cong ◽  
Yingyi Liu ◽  
Ying Gou ◽  
Bin Teng
Keyword(s):  
Theoretical Model ◽  
Velocity Potential ◽  
Wave Force ◽  
The Body ◽  
Hydrodynamic Characteristics ◽  
Linear Potential ◽  
Wave Runup ◽  
Plate Structure ◽  
The Mean ◽  
Drift Force

To improve the seakeeping capability, some devices, such as submerged plates, are often installed on floating structures. The attached plate can not only suppress the motion response but also provide an additional immersed body surface that receives fluid action, aggravating the wave loads. In this study, a theoretical model is developed within the context of linear potential theory to study the hydrodynamic characteristics of a floating column with a submerged plate attached at the bottom. The eigenfunction expansion matching method is applied to obtain the velocity potential, based on which the linear wave force and wave runup can be found immediately. A novel derivation of the mean drift force formulation is developed via the application of Green’s second identity to the velocity potential and its derivative in finite fluid volume surrounding the body. Mean drift force formulation that involves control surfaces is then obtained. With the availability of the velocity potential, semi-analytical solution of the mean drift force on the compound column-plate structure is developed based on, respectively, the derived and the classic far-field formulations. After conducting convergence tests and validating the theoretical model, detailed numerical analysis is performed thereafter based on the theoretical model. The influence of the plate size, such as the radius and height, on the wave force and the associated wave runup is assessed.

scholarly journals Theoretical Analysis of a Vertical Cylindrical Floater in Front of an Orthogonal Breakwater

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 135
Author(s):  
Dimitrios N. Konispoliatis ◽  
Spyridon A. Mavrakos
Keyword(s):  
Hydrodynamic Interaction ◽  
Velocity Potential ◽  
Cylindrical Body ◽  
The Body ◽  
Hydrodynamic Characteristics ◽  
Wave Forces ◽  
Linear Potential ◽  
Method Of Images ◽  
Linear Potential Theory ◽  
Exciting Wave

This study investigates the effect of an orthogonal-shaped reflecting breakwater on the hydrodynamic characteristics of a vertical cylindrical body. The reflecting walls are placed behind the body, which can be conceived as a floater for wave energy absorption. Linear potential theory is assumed, and the associated diffraction and motion radiation problems are solved in the frequency domain. Axisymmetric eigenfunction expansions of the velocity potential are introduced into properly defined ring-shaped fluid regions surrounding the floater. The hydrodynamic interaction phenomena between the body and the adjacent breakwaters are exactly taken into account by using the method of images. Results are presented and discussed concerning the exciting wave forces on the floater and its hydrodynamic coefficients, concluding that the hydrodynamics of a vertical cylindrical body in front of an orthogonally shaped breakwater differ from those in unbounded waters.

Hydrodynamic Analysis of Floating Bodies in General Bathymetry

2005 ◽  
Author(s):  
K. A. Belibassakis
Keyword(s):  
Near Field ◽  
Boundary Integral ◽  
The Body ◽  
Hydrodynamic Characteristics ◽  
Hybrid Technique ◽  
Floating Bodies ◽  
Hydrodynamic Analysis ◽  
Coupled Mode ◽  
Simple Geometry ◽  
Boundary Integral Representation

A hybrid technique, based on the coupled-mode theory developed by Athanassoulis & Belibassakis (1999) and extended to 3D by Belibassakis et al (2001) and Belibassakis & Athanassoulis (2004), which is free of any mild-slope assumption, is used, in conjunction with a boundary integral representation of the near field in the vicinity of the body, to treat the problem of hydrodynamic analysis of floating bodies in the presence of variable bathymetry. Numerical results are presented concerning floating bodies of simple geometry lying over sloping seabeds. With the aid of systematic comparisons, the effects of bottom slope on the hydrodynamic characteristics (hydrodynamic coefficients and responses) are illustrated and discussed.

The Supersonic Flow Past a Slender Ducted Body of Revolution with an Annular Intake

1950 ◽  
Vol 1 (4) ◽  
pp. 305-318
Author(s):  
G. N. Ward
Keyword(s):  
Supersonic Flow ◽  
Velocity Potential ◽  
Operational Calculus ◽  
The Body ◽  
Body Of Revolution ◽  
Internal Flows ◽  
Flow Past ◽  
External Forces ◽  
Internal Pressures ◽  
Slender Body Of Revolution

SummaryThe approximate supersonic flow past a slender ducted body of revolution having an annular intake is determined by using the Heaviside operational calculus applied to the linearised equation for the velocity potential. It is assumed that the external and internal flows are independent. The pressures on the body are integrated to find the drag, lift and moment coefficients of the external forces. The lift and moment coefficients have the same values as for a slender body of revolution without an intake, but the formula for the drag has extra terms given in equations (32) and (56). Under extra assumptions, the lift force due to the internal pressures is estimated. The results are applicable to propulsive ducts working under the specified condition of no “ spill-over “ at the intake.

Hydrodynamic characteristics of vertical and quadrant face pile supported breakwater under oblique waves

2021 ◽  
pp. 147509022110313
Author(s):  
T J Jemi Jeya ◽  
V Sriram ◽  
V Sundar
Keyword(s):  
Experimental Study ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Scattering Parameter ◽  
Oblique Waves ◽  
Test Conditions ◽  
Relative Water ◽  
Identical Test ◽  
Run Up ◽  
Water Depths

This paper presents the results from a comprehensive experimental study on the Quadrant Face Pile Supported Breakwater (QPSB) in two different water depths exposed to three different oblique wave attacks. The results are compared with that for a Vertical face Pile Supported Breakwater (VPSB) for identical test conditions. The paper compares the reflection coefficient, transmission coefficient, energy loss coefficient, non-dimensional pressure, and non-dimensional run-up as a function of the relative water depth and scattering parameter. The results obtained for QPSB are validated with existing results. The salient observations show that QPSB experiences better hydrodynamic performance characteristics than the VPSB under oblique waves.

scholarly journals Hovering performance of Anna's hummingbirds ( Calypte anna ) in ground effect

2014 ◽  
Vol 11 (98) ◽  
pp. 20140505 ◽  
Author(s):  
Erica J. Kim ◽  
Marta Wolf ◽  
Victor Manuel Ortega-Jimenez ◽  
Stanley H. Cheng ◽  
Robert Dudley
Keyword(s):  
Wing Length ◽  
Ground Effect ◽  
The Body ◽  
Plane Angle ◽  
Metabolic Power ◽  
Wingbeat Frequency ◽  
Body Angle ◽  
Induced Flow ◽  
Induced Velocity ◽  
Calypte Anna

Aerodynamic performance and energetic savings for flight in ground effect are theoretically maximized during hovering, but have never been directly measured for flying animals. We evaluated flight kinematics, metabolic rates and induced flow velocities for Anna's hummingbirds hovering at heights (relative to wing length R = 5.5 cm) of 0.7 R , 0.9 R , 1.1 R , 1.7 R , 2.2 R and 8 R above a solid surface. Flight at heights less than or equal to 1.1 R resulted in significant reductions in the body angle, tail angle, anatomical stroke plane angle, wake-induced velocity, and mechanical and metabolic power expenditures when compared with flight at the control height of 8 R . By contrast, stroke plane angle relative to horizontal, wingbeat amplitude and wingbeat frequency were unexpectedly independent of height from ground. Qualitative smoke visualizations suggest that each wing generates a vortex ring during both down- and upstroke. These rings expand upon reaching the ground and present a complex turbulent interaction below the bird's body. Nonetheless, hovering near surfaces results in substantial energetic benefits for hummingbirds, and by inference for all volant taxa that either feed at flowers or otherwise fly close to plant or other surfaces.

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