Propeller-Induced Velocity Field Due to Thickness and Loading Effects

1975 ◽  
Vol 19 (01) ◽  
pp. 44-56
Author(s):  
W. R. Jacobs ◽  
S. Tsakonas
Keyword(s):  
Velocity Field ◽  
High Speed ◽  
Thickness Distribution ◽  
Numerical Procedure ◽  
Thickness Effect ◽  
Thin Body ◽  
Flow Disturbance ◽  
Blade Thickness ◽  
Resultant Velocity ◽  
Induced Velocity

Blade thickness plays a dual role, contributing to the lifting characteristics of the blade because of its nonplanar form as well as to its nonlifting characteristics due to the generation of a symmetrical flow disturbance. However, since the so-called "nonplanar thickness" has been shown to have little effect on the blade pressure distribution and thus presumably to have a negligible effect on the velocity and pressure fields around an operating propeller, the present investigation is limited to the so-called "symmetrical flow disturbance thickness." The effect of this thickness on the oscillatory velocity field around the propeller is studied by means of the "thin body" approach, where the blade section is represented by a source-sink distribution of strength proportional to the slope of the blade thickness distribution. A numerical procedure is devised and adapted to the CDC-6600 high-speed digital computer for the evaluation of the thickness effect on the velocity field. The total propeller-induced velocity field is then obtained by adding the computed velocity components due to thickness, with proper phase, to the results due to propeller loading calculated by means of the lifting-surface theory. Sets of calculations performed for a 3-blade propeller operating in a 3-cycle screen-generated wake and for a 5-blade propeller operating in a realistic hull wake reveal that the effect of thickness in forming the components of the resultant velocity varies from moderate to large, depending on the magnitude of the thickness distribution, on the location of the field point, and on the intensity of the nonuniformity of the inflow field.

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.

Propeller-Rudder Interaction Due to Loading and Thickness Effects

1975 ◽  
Vol 19 (02) ◽  
pp. 99-117
Author(s):  
S. Tsakonas ◽  
W. R. Jacobs ◽  
M. R. All
Keyword(s):  
Numerical Procedure ◽  
Thickness Effect ◽  
Thin Body ◽  
Propeller Blade ◽  
Blade Thickness ◽  
The Mean ◽  
Axial Clearance ◽  
Lifting Surfaces ◽  
Thrust And Torque ◽  
Interaction Problem

The previous analysis of the propeller-rudder interaction problem by means of the lifting-surface theory has been modified to include the effects of thickness of both surfaces. The effect of propeller blade thickness and rudder thickness on the "flow displacement" in the field is taken into account by the "thin body" approach. The blade thickness effect on the loading of the propeller blade due to its nonplanar form, being small, is neglected. The resulting onset velocities on both lifting surfaces due to the thickness effects on the flow field are incorporated, together with the onset velocities due to hull wake and camber and incident angle of the surfaces, into the existing iterative procedure. The numerical procedure, which has been adapted to the CDC 6600 high speed digital computer, furnishes the steady and time-dependent pressure distributions on both lifting surfaces and the resulting hydrodynamic forces and moments. From the limited number of calculations, it is seen that the thickness effect does not change the general conclusions reached in the previous study of the interaction problem. The interaction apparently is governed principally by the loading effects. The mean and blade-frequency thrust and torque and the mean rudder force and moment are very little affected by the inclusion of thickness even at the smallest possible axial clearance between propeller and rudder. The influence of thickness is greater on the propeller bearing forces and bending moments, on the steady-state values more than on the unsteady, and decreases with increase in axial clearance. The thickness effect is most pronounced in the case of unsteady rudder forces and moments at certain axial clearances, varying cyclically with clearance.

Propeller Blade Pressure Distribution Due to Loading and Thickness Effects

1979 ◽  
Vol 23 (02) ◽  
pp. 89-107 ◽  
Author(s):  
S. Tsakonas ◽  
W. R. Jacobs ◽  
M. R. Ali
Keyword(s):  
Pressure Distribution ◽  
High Speed ◽  
Computational Procedure ◽  
Thin Body ◽  
Operator Technique ◽  
Surface Integral ◽  
Flow Distortion ◽  
Cavitation Inception ◽  
Blade Thickness ◽  
Loading Effects

A theoretical approach is developed and a computational procedure adaptable to a high-speed digital computer is established for the evaluation of the blade pressure distribution of a marine propeller due to thickness and loading effects. The dual role of the blade thickness is considered. The contribution of the "non-planar thickness" to the propeller loading and pressure distribution and the effect of the "flow distortion thickness" are studied by means of the "thin body" approximation. The surface integral equation which relates the unknown loading to the known velocity distribution on the blades is solved by the mode approach in conjunction with the "lift operator" technique. The analysis treats both design and off-design conditions in steady-state and unsteady flows, and the proper chordwise modes are selected for each condition. The numerical solution yields the blade loading and resulting hydrodynamic forces and moments and blade bending moments, and, in addition, the blade pressure distributions on each blade face due to both loading and thickness effects, thus providing information necessary for the prediction of cavitation inception. Calculations have been performed for a set of three 3-bladed propellers of different EAR operating in a screen-generated wake, for comparison with experimental data.

Influence of rotating magnetic field on Maxwell saturated ferrofluid flow over a heated stretching sheet with heat generation/absorption

2019 ◽  
Vol 20 (5) ◽  
pp. 502 ◽  
Author(s):  
Aaqib Majeed ◽  
Ahmed Zeeshan ◽  
Farzan Majeed Noori ◽  
Usman Masud
Keyword(s):  
Magnetic Field ◽  
Temperature Field ◽  
Velocity Field ◽  
Differential Equations ◽  
Heat Transport ◽  
Viscous Dissipation ◽  
Heat Generation ◽  
Fluid Motion ◽  
Numerical Procedure ◽  
The Impact

This article is focused on Maxwell ferromagnetic fluid and heat transport characteristics under the impact of magnetic field generated due to dipole field. The viscous dissipation and heat generation/absorption are also taken into account. Flow here is instigated by linearly stretchable surface, which is assumed to be permeable. Also description of magneto-thermo-mechanical (ferrohydrodynamic) interaction elaborates the fluid motion as compared to hydrodynamic case. Problem is modeled using continuity, momentum and heat transport equation. To implement the numerical procedure, firstly we transform the partial differential equations (PDEs) into ordinary differential equations (ODEs) by applying similarity approach, secondly resulting boundary value problem (BVP) is transformed into an initial value problem (IVP). Then resulting set of non-linear differentials equations is solved computationally with the aid of Runge–Kutta scheme with shooting algorithm using MATLAB. The flow situation is carried out by considering the influence of pertinent parameters namely ferro-hydrodynamic interaction parameter, Maxwell parameter, suction/injection and viscous dissipation on flow velocity field, temperature field, friction factor and heat transfer rate are deliberated via graphs. The present numerical values are associated with those available previously in the open literature for Newtonian fluid case (γ 1 = 0) to check the validity of the solution. It is inferred that interaction of magneto-thermo-mechanical is to slow down the fluid motion. We also witnessed that by considering the Maxwell and ferrohydrodynamic parameter there is decrement in velocity field whereas opposite behavior is noted for temperature field.

Quantitative Analysis of Reynolds and Navier–Stokes Based Modeling Approaches for Isothermal Newtonian Elastohydrodynamic Lubrication

2021 ◽  
Vol 143 (12) ◽  
Author(s):  
Leoluca Scurria ◽  
Tommaso Tamarozzi ◽  
Oleg Voronkov ◽  
Dieter Fauconnier
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Thickness Distribution ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Shear Stresses ◽  
Low Viscosity ◽  
Fluid Film Thickness

Abstract When simulating elastohydrodynamic lubrication, two main approaches are usually followed to predict the pressure and fluid film thickness distribution throughout the contact. The conventional approach relies on the Reynolds equation to describe the thin lubricant film, which is coupled to a Boussinesq description of the linear elastic deformation of the solids. A more accurate, yet a time-consuming method is the use of computational fluid dynamics in which the Navier–Stokes equations describe the flow of the thin lubricant film, coupled to a finite element solver for the description of the local contact deformation. This investigation aims at assessing both methods for different lubrication conditions in different elastohydrodynamic lubrication (EHL) regimes and quantify their differences to understand advantages and limitations of both methods. This investigation shows how the results from both approaches deviate for three scenarios: (1) inertial contributions (Re > 1), i.e., thick films, high speed, and low viscosity; (2) high shear stresses leading to secondary flows; and (3) large deformations of the solids leading to inaccuracies of the Boussinesq equation.

Optimization and Investigation on the Impact of Centrifugal Impeller Blade Thickness Distribution on Hydro-Induced Vibration

2018 ◽  
Author(s):  
B. Qian ◽  
D. Z. Wu
Keyword(s):  
Secondary Flow ◽  
Thickness Distribution ◽  
Suction Side ◽  
Centrifugal Impeller ◽  
Impeller Blade ◽  
Streamwise Location ◽  
Unbalanced Rotor ◽  
Blade Thickness ◽  
Vibration Performance ◽  
The Impact

The vibration performance of centrifugal impellers is of great importance for pumps in some application areas such as automobiles and ships. Apart from mechanical excitations for instance, unbalanced rotor and misalignment, attentions should be concentrated on the hydraulic excitations. The complex internal secondary flow in the centrifugal impeller brings degradation on both hydraulic and vibration performances. On the purpose of repressing the internal secondary flow and alleviating vibration, an attempt of optimization by controlling the thickness distribution of centrifugal impeller blade is given. The vibration performances of the impellers are investigated numerically and experimentally. Meanwhile, further study on the mechanism of the influence of the thickness distribution optimization on vibration is conducted. There is a relative velocity gradient from suction side (SS) to pressure side (PS) due to the Coriolis force, which causes non-uniformity of energy distribution. By means of thickness distribution optimization, the impeller blade angle on the PS and SS along the blade-aligned (BA) streamwise location is respectively modified and therefore the flow field can be improved.

STAEBL/General Composites With Hygrothermal Effects (STAEBL/GENCOM)

1988 ◽  
Vol 110 (2) ◽  
pp. 301-305
Author(s):  
R. Rubinstein
Keyword(s):  
Composite Laminates ◽  
Fiber Composite ◽  
Thickness Distribution ◽  
Turbine Blades ◽  
Material Design ◽  
Computer Code ◽  
Forced Response ◽  
General Description ◽  
Blade Thickness ◽  
Design Variables

A computer code has been developed to perform structural optimization of turbine blades made from angle ply fiber composite laminates. Design variables available for optimization include geometric parameters such as blade thickness distribution and root chord, and composite material parameters such as ply angles and numbers of plies of each constituent material. Design constraints include resonance margins, forced response margins, maximum stress, and maximum ply combined stress. A general description of this code is given. Design optimization studies for typical blades are presented.

scholarly journals Improved convergence and stability properties in a three-dimensional higher-order ice sheet model

2011 ◽  
Vol 4 (3) ◽  
pp. 1569-1610
Author(s):  
J. J. Fürst ◽  
O. Rybak ◽  
H. Goelzer ◽  
B. De Smedt ◽  
P. de Groen ◽  
...  
Keyword(s):  
Velocity Field ◽  
Finite Difference ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Higher Order ◽  
Velocity Fields ◽  
Force Balance ◽  
Staggered Grid ◽  
Comparison Results ◽  
Resultant Velocity

Abstract. We present a novel finite difference implementation of a three-dimensional higher-order ice sheet model that performs well both in terms of convergence rate and numerical stability. In order to achieve these benefits the discretisation of the governing force balance equation makes extensive use of information on staggered grid points. Using the same iterative solver, an existing discretisation that operates exclusively on the regular grid serves as a reference. Participation in the ISMIP-HOM benchmark indicates that both discretisations are capable of reproducing the higher-order model inter-comparison results. This allows a direct comparison not only of the resultant velocity fields but also of the solver's convergence behaviour which holds main differences. First and foremost, the new finite difference scheme facilitates convergence by a factor of up to 7 and 2.6 in average. In addition to this decrease in computational costs, the precision for the resultant velocity field can be chosen higher in the novel finite difference implementation. For high precisions, the old discretisation experiences difficulties to converge due to large variation in the velocity fields of consecutive Picard iterations. Finally, changing discretisation prevents build-up of local field irregularites that occasionally cause divergence of the solution for the reference discretisation. The improved behaviour makes the new discretisation more reliable for extensive application to real ice geometries. Higher precision and robust numerics are crucial in time dependent applications since numerical oscillations in the velocity field of subsequent time steps are attenuated and divergence of the solution is prevented. Transient applications also benefit from the increased computational efficiency.

scholarly journals High-Speed Rotor Analytical Dynamics on Flexible Foundation Subjected to Internal and External Excitation

2016 ◽  
Vol 46 (4) ◽  
pp. 3-18
Author(s):  
Venelin S. Jivkov ◽  
Evtim V. Zahariev
Keyword(s):  
Gas Turbines ◽  
High Speed ◽  
Asymptotic Methods ◽  
Numerical Procedure ◽  
Rigid Bodies ◽  
Dynamics Simulation ◽  
Geometrical Approach ◽  
Rotating Machine ◽  
Exciting Frequency ◽  
Stiffness And Damping

Abstract The paper presents a geometrical approach to dynamics simulation of a rigid and flexible system, compiled of high speed rotating machine with eccentricity and considerable inertia and mass. The machine is mounted on a vertical flexible pillar with considerable height. The stiffness and damping of the column, as well as, of the rotor bearings and the shaft are taken into account. Non-stationary vibrations and transitional processes are analyzed. The major frequency and modal mode of the flexible column are used for analytical reduction of its mass, stiffness and damping properties. The rotor and the foundation are modelled as rigid bodies, while the flexibility of the bearings is estimated by experiments and the requirements of the manufacturer. The transition effects as a result of limited power are analyzed by asymptotic methods of averaging. Analytical expressions for the amplitudes and unstable vibrations throughout resonance are derived by quasi-static approach increasing and decreasing of the exciting frequency. Analytical functions give the possibility to analyze the influence of the design parameter of many structure applications as wind power generators, gas turbines, turbo-generators, and etc. A numerical procedure is applied to verify the effectiveness and precision of the simulation process. Nonlinear and transitional effects are analyzed and compared to the analytical results. External excitations, as wave propagation and earthquakes, are discussed. Finite elements in relative and absolute coordinates are applied to model the flexible column and the high speed rotating machine. Generalized Newton - Euler dynamics equations are used to derive the precise dynamics equations. Examples of simulation of the system vibrations and nonstationary behaviour are presented.

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.

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