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1
Construction of complex potentials for multiply connected domain
Ivanshin Pyotr N.
Journal of Applied Analysis
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2021
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Vol. 27, nr 2
209--217
EN
The method of reduction of a Fredholm integral equation to the linear system is generalized to construction of a complex potential - an analytic function in an unbounded multiply connected domain with a simple pole at infinity which maps the domain onto a plane with horizontal slits. We consider a locally sourceless, locally irrotational flow on an arbitrary given n-connected unbounded domain with impermeable boundary. The complex potential has the form of a Cauchy integral with one linear and n logarithmic summands. The method is easily computable.
2
Content available The prediction of hull gesture and flow around ship based on Taylor expansion boundary element method
Gong Jiaye, Li Yunbo
Polish Maritime Research
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2019
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nr 2
198--211
EN
Based on the potential flow theory and traditional boundary element method (BEM), Taylor expansion boundary element method (TEBEM) is introduced in this paper for the prediction of the flow field around ship, as a result, hull gesture and pressure distribution on hull surface are obtained. By this method, dipole strength of every field point is expanded in Taylor expansion, so that approximately continuous hull and free surface boundary condition could be achieved. To close the new equation system, the boundary condition of tangent velocity in every control point is introduced. With the simultaneous solving of hull boundary condition and free surface condition, the disturbance velocity potential could be obtained. The present method is used to predict the flow field and hull gesture of Wigley parabolic hull, Series 60 and KVLCC2 models. To validate the numerical model for full form ship, the wave profile, the computed hull gesture and hull surface pressure of KVLCC2 model are compared with experimental results.
3
Content available A Comparison of Simplified Two-dimensional Flow Models Exemplified by Water Flow in a Cavern
Prybytak D., Zima P.
Archives of Hydro-Engineering and Environmental Mechanics
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2017
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Vol. 64, nr 3-4
141--154
EN
The paper shows the results of a comparison of simplified models describing a two-dimensional water flow in the example of a water flow through a straight channel sector with a cavern. The following models were tested: the two-dimensional potential flow model, the Stokes model and the Navier-Stokes model. In order to solve the first two, the boundary element method was employed, whereas to solve the Navier-Stokes equations, the open-source code library OpenFOAM was applied. The results of numerical solutions were compared with the results of measurements carried out on a test stand in a hydraulic laboratory. The measurements were taken with an ADV probe (Acoustic Doppler Velocimeter). Finally, differences between the results obtained from the mathematical models and the results of laboratory measurements were analysed.
4
Content available remote The impact of the Dirichlet boundary conditions on the convergence of the discretized system of nonlinear equations for potential problems
Kucwaj J.
Computer Assisted Methods in Engineering and Science
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2016
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Vol. 23, no. 1
69--81
EN
The purpose of this paper is the analysis of numerical approaches obtained by describing the Dirichlet boundary conditions on different connected components of the computational domain boundary for potential flow, provided that the domain is a rectangle. The considered problem is a potential flow around an airfoil profile. It is shown that in the case of a rectangular computational domain with two sides perpendicular to the speed direction, the potential function is constant on the connected components of these sides. This allows to state the Dirichlet conditions on the considered parts of the boundary instead of the potential jump on the slice connecting the trail edge with the external boundary. Furthermore, the adaptive remeshing method is applied to the solution of the considered problem.
5
Content available Accuracy of Potential Flow Methods to Solve Real-time Ship-Tug Interaction Effects within Ship Handling Simulators
Jayarathne B. N., Ranmuthugala D., Fei J.
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
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2014
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Vol. 8 no. 4
497--504
EN
The hydrodynamic interaction effects between two vessels that are significantly different in size operating in close proximity can adversely affect the safety and handling of these vessels. Many ship handling simulator designers implement Potential Flow (PF) solvers to calculate real-time interaction effects. However, these PF solvers struggle to accurately predict the complicated flow regimes that can occur, for example as the flow passes a wet transom hull or one with a drift angle. When it comes to predicting the interaction effects on a tug during a ship assist, it is essential to consider the rapid changes of the tug’s drift angle, as the hull acts against the inflow creating a complicated flow regime. This paper investigates the ability of the commercial PF solver, Futureship®, to predict the accurate interaction effects acting on tugs operating at a drift angle during ship handling operations through a case study. This includes a comparison against Computation Fluid Dynamics (CFD) simulations and captive model tests to examine the suitability of the PF method for such duties. Although the PF solver can be tuned to solve streamline bodies, it needs further improvement to deal with hulls at drift angles.
6
Content available remote Zastosowanie metody panelowej do analizy hydrodynamicznej śruby okrętowej
Kulczyk J., Tabaczek T.
Inżynieria Maszyn
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2006
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R. 11, z. 2/3
114-148
PL
Autorzy zastosowali metodę panelową z powierzchniowym rozkładem wirowości do modelowania przepływu potencjalnego wokół śruby okrętowej. Powierzchnia skrzydła i piasty została zastąpiona panelami z wirowością. Ślad hydromechaniczny za skrzydłem modelowany był przy pomocy włókien wirowych o kształcie linii śrubowej. Wpływ lepkości został uwzględniony w sposób przybliżony, przez zastosowanie empirycznych współczynników oporu profilu. Model przeznaczony jest do analizy hydrodynamicznej śrub okrętowych pracujących w obwodowo niejednorodnym polu prędkości. Umożliwia obliczanie sił hydrodynamicznych działających na skrzydła i momentu na wale śrubowym, oraz rozkładu ciśnienia na powierzchni skrzydeł.
EN
In the paper the mathematical model of hydraulic system with accumulator was presented. The model was based on electrical analogy for laminar flow in second phase hydraulic cylinder starting. Calculations were done and diagrams were prepared: flow rate, pressure in accumulator and in hydraulic cylinder and piston stroke.
7
Content available remote Green water computed with a spline-based collocation method for potential flow
Trulsen K., Spjelkavik B., Mehlum E.
International Journal of Applied Mechanics and Engineering
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2002
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Vol. 7, no 1
107-123
EN
We present a fully nonlinear method for numerical simulation of the inundation of an arbitrary solid body in large waves. The method is based on potential flow and is therefore expected to break down when wave breaking sets in. The method is expected to be useful to predict the initial phase of inundation and can thus give the flow field as initial condition to some other method more appropriate for the later stages of green water. We employ an artificial tri-harmonic potential inside the solid body in order to avoid introducing singularities in the solution. Spline-based basis potentials are constructed and are used in a collocation spectral method. We illustrate the method for the special case of waves inundating a truncated cylinder.
8
Content available remote Remarks on Plane, Steady, Creeping Flows Generated by Singularities
Klonowska-Prosnak M.E., Cześnik P.
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2002
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Vol. 50, Nr 1
45--69
EN
Two properties of plane, steady, creeping flow generated in the infinite domain around a given contour by a single singularity are investigated in the paper. The first property concerns velocity field. It is shown, that stream uniform at infinity must occur automatically in this case, and formulae for velocity of the stream are derived. The second property concerns similarity of streamline pattern of such flow, and the potential one, generated around the same contour by the same singularity. Investigation of the both properties concerns - in particular: a disc, an ellipse and the airfoil sections NACA 0012, RAE 2822.
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