Three-Dimensional Approach to the Gust Problem for a Screw Propeller

1964 ◽  
Vol 8 (02) ◽  
pp. 29-53 ◽  
Author(s):  
J. Shioiri ◽  
S. Tsakonas
Keyword(s):  
Three Dimensional ◽  
Marine Propeller ◽  
Dimensional Approach ◽  
Nonstationary Flow ◽  
Surface Integral ◽  
Surface Approach ◽  
Surface Integral Equation ◽  
Screw Propeller ◽  
Blade Area ◽  
Unsteady Lift

The unsteady lifting-surface approach is utilized for the hull-induced gust problem in the marine propeller case and the corresponding surface integral equation is solved under the Weissinger approximation. The applicability of the Weissinger method to the nonstationary flow case is studied. The kernel function is evaluated after some mathematical simplification. From numerical calculations of unsteady lift due to the gust, which are restricted to a four-bladed propeller of sector form blade with different blade-area ratios and various pitch-diameter ratios, conclusions are drawn as to the dependence of unsteady lift on such important parameters as the blade-area and pitch-diameter ratios, and the nature of the three-dimensional effects in the unsteady gust problem is clarified.

Unsteady Lifting Surface Theory for a Marine Propeller of Low Pitch Angle With Chordwise Loading Distribution

1965 ◽  
Vol 9 (03) ◽  
pp. 79-101 ◽  
Author(s):  
S. Tsakonas ◽  
W. R. Jacobs
Keyword(s):  
Incidence Angle ◽  
Three Dimensional ◽  
Weighted Average ◽  
Marine Propeller ◽  
Surface Integral ◽  
Dimensional Solution ◽  
Surface Theory ◽  
Lifting Surface ◽  
Blade Area ◽  
Thrust And Torque

This study is third in a series of investigations applying the unsteady lifting-surface theory to the marine propeller case. In the present investigation, the surface integral equation is solved for a mathematical model where the chordwise loading is taken as the first term of Birnbaum's lift distribution (flat-plate chordwise distribution), in conjunction with Glauert's lift operator, which, in essence, satisfies the chordwise boundary conditions by a weighted average. It is shown that this model is an improvement over the modified Weissinger model used previously in this series, because it contains as a nucleus the exact two-dimensional solution, and thus it provides a sounder basis for determining the three-dimensional effects. The blade-loading is determined for a propeller operating in flow disturbances induced by the presence of a hull and by the blade-camber and incidence-angle effects. The stationary loading obtained by the present model is less than that obtained by the modified Weissinger model, whereas the nonstationary loading is slightly larger. The results of numerical calculations are applied to the problem of propeller vibratory thrust and torque, and comparison is made with previous theoretical and experimental values. Conclusions of the earlier studies as to the dependence of loading on the important parameters—blade-area ratio, aspect ratio and pitch—are confirmed by the present results.

The Unsteady Loading on a Marine Propeller in a Nonuniform Flow

1964 ◽  
Vol 8 (05) ◽  
pp. 29-38
Author(s):  
Michael D. Greenberg
Keyword(s):  
Free Stream ◽  
Marine Propeller ◽  
Nonuniform Flow ◽  
Surface Integral ◽  
Practical Applications ◽  
Vortex Model ◽  
Surface Integral Equation ◽  
Lifting Surface ◽  
Finite Wing ◽  
Unsteady Loading

The lifting-surface integral equation governing the unsteady loading on a marine propeller in a nonuniform free stream is derived using a classical vortex model. The induced downwash is split into a part corresponding to a locally tangent flat finite wing and wake, plus parts corresponding to the effects of the "helicoidal deviation" from this, of the true blade and wake, and the interference from the other blades and their wakes. Strip-type approximations are tolerated on these terms while a lifting-surface formulation is retained for the dominant finite flat-wing portion. A simple numerical example is carried out and these effects are indeed found to be quite small; so small, in fact, that it may suffice to retain only the flat finite-wing terms in practical applications.

scholarly journals SURFACE INTEGRAL EQUATION FORMULATION FOR THE ANALYSIS OF SINGLE AND MULTI-LAYER DIELECTRIC ANTENNAS

2020 ◽  
Author(s):  
John Stevenson
Keyword(s):  
Integral Equation ◽  
Electromagnetic Scattering ◽  
Fast Multipole Method ◽  
Three Dimensional ◽  
Dielectric Materials ◽  
Layered Composite ◽  
Surface Integral ◽  
Dielectric Resonator Antennas ◽  
Surface Integral Equation ◽  
Integral Equation Formulation

This article studies numerically the electromagnetic scattering properties of three dimensional (3D), arbitrary shaped dielectric resonator antennas which are composed of single and multi-layered (composite) dielectric materials. Using the equivalence principle and the integral equation techniques, we first derive a surface integral equation (SIE) formulation which produces well-conditioned matrix equation. We then develop an algorithm to speed up the matrix-vector multiplications by employing the well-known method of moments (MoM) and the multilevel fast multipole method (MLFMM) on personal computer (PC) clusters. To solve the obtained integral equations, we apply a Galerkin scheme and choose the basis and testing functions as Rao-Wilton-Glisson (RWG) defined on planar patches. Finally, we present some 3D numerical examples to demonstrate the validity and accuracy of the proposed approach.

Coupled BEM and FDM Conjugate Analysis of a Three-Dimensional Air-Cooled Turbine Vane

2009 ◽  
Author(s):  
Zhenfeng Wang ◽  
Peigang Yan ◽  
Hongyan Huang ◽  
Wanjin Han
Keyword(s):  
Heat Transfer ◽  
Integral Equation ◽  
Conjugate Heat Transfer ◽  
Analytic Solution ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Surface Integral ◽  
Surface Integral Equation ◽  
Commercial Code ◽  
Good Agreement

A coupled boundary element method (BEM) and finite difference method (FDM) are applied to solve conjugate heat transfer problem of a three-dimensional air-cooled turbine blade. A loosely coupled strategy is adopted, in which each set of field equations is solved to provide boundary conditions for the other. In the fluid region, computation code (HIT-NS CODE) adopts the FDM to solve the Navier-Stokes equations. In the solid region, the BEM is adopted to resolve the conduction heat transfer equations. An iterated convergence criterion is the continuity of temperature and heat flux at the fluid-solid interface. The solid heat transfer computation code (3D-BEM CODE) is validated by comparing with the results of an analytic solution and the results of commercial code, the results from 3D-BEM CODE have a good agreement with the analytic solution and commercial code results. The BEM uses a weighted residual method to make the Laplace equation convert into a surface integral equation and the surface integral equation is discretized. The BEM avoids the complicated mesh needed in other computation methods and saves the computation time. In addition, the BEM has the characteristic of a combination of an analytic and a discrete solution. So the BEM solutions of heat conduction problems are more accurate. The results of the coupling computation code (HIT-NS-3DBEM CODE) have a good agreement with the experimental results. The adiabatic condition result is different from the results of experiment and code calculation. So the results from conjugate heat transfer analysis are more accurate and they are closer to realistic thermal environment of turbines. Four turbulence models are applied: K-epsilon model, K-omega model, K-omega (SST-Gamma Theta) model, and B-L model adopted by computation code. Different turbulence models gives different the results of vane wall temperature. Comparing the four turbulence models, the different turbulence models can exactly simulate the flow field, but they can not give exact values for the heat conduction simulation in the boundary layer. The result of K-Omega (SST-Gamma Theta) turbulence model is closer to the experimental data.

scholarly journals Homogenization of three-dimensional metamaterial objects and validation by a fast surface-integral equation solver

2013 ◽  
Vol 21 (19) ◽  
pp. 21714 ◽  
Author(s):  
Xing-Xiang Liu ◽  
Jackson W. Massey ◽  
Ming-Feng Wu ◽  
Kristopher T. Kim ◽  
Robert A. Shore ◽  
...  
Keyword(s):  
Integral Equation ◽  
Three Dimensional ◽  
Surface Integral ◽  
Surface Integral Equation

scholarly journals Electromagnetic Scattering Analysis of SHDB Objects Using Surface Integral Equation Method

Photonics ◽  
2020 ◽  
Vol 7 (4) ◽  
pp. 134
Author(s):  
Beibei Kong ◽  
Pasi Ylä-Oijala ◽  
Ari Sihvola
Keyword(s):  
Boundary Condition ◽  
Integral Equation ◽  
Electromagnetic Scattering ◽  
Three Dimensional ◽  
Circular Disk ◽  
Integral Equation Method ◽  
Surface Integral ◽  
Three Dimensional Objects ◽  
Surface Integral Equation ◽  
Scalar Equations

A surface integral equation (SIE) method is applied in order to analyze electromagnetic scattering by bounded arbitrarily shaped three-dimensional objects with the SHDB boundary condition. SHDB is a generalization of SH (Soft-and-Hard) and DB boundary conditions (at the DB boundary, the normal components of the D and B flux densities vanish). The SHDB boundary condition is a general linear boundary condition that contains two scalar equations that involve both the tangential and normal components of the electromagnetic fields. The multiplication of these scalar equations with two orthogonal vectors transforms them into a vector form that can be combined with the tangential field integral equations. The resulting equations are discretized and converted to a matrix equation with standard method of moments (MoM). As an example of use of the method, we investigate scattering by an SHDB circular disk and demonstrate that the SHDB boundary allows for an efficient way to control the polarization of the wave that is reflected from the surface. We also discuss perspectives into different levels of materialization and realization of SHDB boundaries.

Shifting perspectives: method, media and the complex image

1998 ◽  
Vol 10 (1-3) ◽  
pp. 100-108 ◽  
Author(s):  
Alicia Colson ◽  
Ross Parry
Keyword(s):  
Image Processing ◽  
Three Dimensional ◽  
Geographical Location ◽  
Spatial Relationship ◽  
Two Dimensional ◽  
Dimensional Approach ◽  
Complex Image ◽  
Cultural Resonance

This article argues that the analysis of a threedimensional image demanded a three-dimensional approach. The authors realise that discussions of images and image processing inveterately conceptualise representation as being flat, static, and finite. The authors recognise the need for a fresh acuteness to three-dimensionality as a meaningful – although problematic – element of visual sources. Two dramatically different examples are used to expose the shortcomings of an ingrained two-dimensional approach and to facilitate a demonstration of how modern (digital) techniques could sanction new historical/anthropological perspectives on subjects that have become all too familiar. Each example could not be more different in their temporal and geographical location, their cultural resonance, and their historiography. However, in both these visual spectacles meaning is polysemic. It is dependent upon the viewer's spatial relationship to the artifice as well as the spirito-intellectual viewer within the community. The authors postulate that the multi- faceted and multi-layered arrangement of meaning in a complex image could be assessed by working beyond the limitations of the two-dimensional methodological paradigm and by using methods and media that accommodated this type of interconnectivity and representation.

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