| 1. |
- Andersson, Jennie, 1986, et al.
(författare)
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CFD Simulations of the Japan Bulk Carrier Test Case
- 2015
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Ingår i: NUMERICAL TOWING TANK SYMPOSIUM. 18TH 2015. (NUTTS 2015). - 9781510815858
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Konferensbidrag (refereegranskat)abstract
- This computational fluid dynamics (CFD) validation study is performed as a foundation for further studies with focus on the interaction effects between propulsor and hull. To be able to study the interaction effects, an appropriate CFD methodology need to be established and validated for a bare hull, for the propulsion unit and for the combined system, a self-propelled hull. The work to validate a CFD model is initiated through the use of the JBC, Japan Bulk Carrier, open test case. The JBC test case is developed for the 2015 workshop on CFD in Ship Hydrodynamics. The tested JBC only exists in model scale with scale factor 1:40 (LPP = 7 m). Model ship speed is 1.179 m/s, corresponding to Fn = 0.142 and 14.5 kn, only calm water conditions are tested. There are two variants of the hull, with and without an energy saving device, within this study the one without is used. Test data used for validation of the CFD results are from towing tank experiments at NMRI. The aim of further studies is to study propulsor hull interaction in full scale, but since detailed test data in full scale is limited, all computations will be performed in model scale. The commercial CFD package STAR-CCM+, a finite volume method solver, is employed for all studies. STAR-CCM+ is a general purpose CFD code used for a wide variety of applications. It solves the conservation equations for momentum and mass, turbulence quantities and volume fraction of water using a segregated solver based on the SIMPLE-algorithm. A 2nd order upwind discretization scheme in space is used. It is of interest to study how a general purpose code can perform for detailed ship hydrodynamic analyses and which limitations that could be identified.
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| 2. |
- Andersson, Jennie, 1986, et al.
(författare)
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Energy balance analysis of a propeller in open water
- 2018
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Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018. ; 158, s. 162-170
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a methodology based on control volume analysis of energy, applied on Computational Fluid Dynamics (CFD) results, for analyzing ship propulsion interaction effects as a complement to the well-established terminology, including thrust deduction, wake fraction and propulsive efficiency. The method, titled Energy Balance Analysis, is demonstrated on a propeller operating in open water. Through consideration of a complete energy balance, including kinetic energy flux, turbulent kinetic energy flux, internal energy flux (originating from dissipation) and pressure work, all possible hydrodynamic losses are included in the analysis, implying that it should be possible to avoid sub-optimized solutions. The results for different control volumes and grid refinements are compared. The deviation of the power obtained from the proposed energy balance analysis relative to the power based on integrated forces on the propeller is less than 1%. The method is considered promising for analyzing and understanding propulsor hull interaction for conventional, as well as novel propulsion configurations. The energy balance analysis is conducted as a post-processing step and could be used in automated optimization procedures.
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| 3. |
- Eslamdoost, Arash, 1982, et al.
(författare)
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Analysis of Propeller-Hull Interaction Phenomena on a Self-Propelled Axisymmetric Body
- 2017
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Ingår i: 5th Int. Symposium on Marine Propulsor.
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Konferensbidrag (refereegranskat)abstract
- The Reynolds Transport theorem for energy is used to study propeller-hull interaction effects by analyzing different components of energy flux through a control volume around a self-propelled vessel. These components are the axial kinetic energy, the transversal kinetic energy, the turbulent kinetic energy, the internal energy and the pressure work. This energy balance approach is here used to study the influence of propeller diameter on the propulsive power. To this end, propellers of different diameters have been studied in behind condition. In order to keep the incoming wake into the propellers as simple as possible, an axi-symmetric hull shape is employed. The energy fluxes are calculated employing a RANS approach to solve the momentum transport and continuity equations together with the energy equation (the heat transfer equation in fluid). The latter equation is solved to compute the internal energy. The results show a minor difference on interaction effects. However, analyzing the energy flux components and their contribution to the total energy provides an extra tool for better understanding of the interaction effects.
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| 4. |
- Eslamdoost, Arash, 1982, et al.
(författare)
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Waterjet Self-Propulsion Simulation: A Body-Force Approach for Modelling the Pump
- 2017
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Ingår i: 11th Symposium on High Speed Marine Vehicles (HSMV 2017).
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Konferensbidrag (refereegranskat)abstract
- The waterjet pump can be treated in different ways in a Reynolds Averaged Navier-Stokes based numerical simulation. The most accurate model is to resolve the complete pump geometry with rotating impeller (e.g. rigid body rotation). Alternatively, in order to reduce the computational cost, a frozen rotor approach or a body-force model can be employed. In this paper, different body-force models are utilized to simulate the waterjet pump in self-propulsion. Then the body-force models are evaluated through a quantitative comparison of the pump flow rate, head rise and the detailed flow at the nozzle exit with the results obtained from the more sophisticated rigid body rotation and frozen rotor techniques. This evaluation reveals that a body-force model for pump induces very similar effects on the flow in comparison to the more sophisticated methods and can reliably be used for modelling waterjet-hull interaction effects in self-propulsion.
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| 8. |
- Hyensjö, Marko, 1968-
(författare)
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Fibre Orientation Modelling Applied to Contracting Flows Related to Papermaking
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main goal of this work was to develop numerical models for studying the behaviour of fibres in an accelerated flow. This is of special interest for e.g. papermaking. The early stage of the paper manufacturing process determines most of the final properties of a paper sheet. The complexity of studying the flow of fibre suspensions both experimentally and numerically emphasises a need for new ideas and developments. By means of solving the evolution of a convective-dispersion equation, i.e. the Fokker-Planck equation, a fully 3D approach with respect to the position and the two fibre angles, polar and azimuthal angles, following a streamline is presented. As an input to the fibre orientation model the turbulent flow field is solved by Computational Fluid Dynamics (CFD) with second-order closure in the turbulence model. In this work two new hypotheses have been presented for the variation of the non-dimensional rotational diffusivity with non-dimensional fibre length, Lf /η and the Reynolds number based on the Taylor micro-scale of the turbulence, Reλ Parameters for the two new hy- potheses and earlier models are determined with the aim of achieving a general relation and a value of the rotational dispersion coeffcient of stiff fibres in an anisotropic turbulent fluid flow. Earlier modelling work has been focused on solving the planar approach, i.e. assuming all fibres to be in one plane. This planar approach is discussed and compared with the fully 3D approach and its validity is evaluated. The optimization of parameters for the different hypotheses correlated on a central streamline, showed a good agreement with an independent experimental result in the undisturbed region. Moreover, it is particularly interesting that the boundary layer region and the wake region are predicted fairly well and the phenomena are well described, which has not been the case earlier. It seems that the new hypothesis based on the variation of the non-dimensional fibre length, Lf /η gives the best correlation in these shear-layer regions. Further- more it was established that the planar approach fails to predict shear layers, i.e. the boundary layer and the wake regions. As emphasized in the theory section, the planar formulation is strictly valid only if all fibres are oriented in one plane, which is not the case in the shear layers. In the undisturbed region, the 3D and the planar approaches, agree in their results. This leads to the conclusion that both approaches are suitable when shear layers are not studied.
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| 9. |
- Hyensjö, Marko, et al.
(författare)
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Modelling a Turbulent Dilute Fibre Suspension in a Planar Contraction : Effect of Vane Types, Vane Position and Wall Boundary Layer on Fibre Orientation Distribution
- 2004
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Ingår i: Proceedings of the 5th International Conference on Multiphase Flow, ICMF’04 Yokohama, Japan.
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Konferensbidrag (refereegranskat)abstract
- A model of the effect of turbulence generating vanes and its location in a planar contraction for predicting fibre orientation distribution is proposed. Simultaneously with CFD simulations and with experimental data, the non-dimensional rotational dispersion coefficient has been determined for the extended 1D headbox model. Furthermore the behavior of turbulence generating vanes types, i.e. blunt and tapered, and the location of such has been studied. For different streamlines in the contracting channel, the one dimensional fibre orientation distribution model is solved, and the fibre orientation distribution is studied along streamlines near the vane wall and vane tip and further away. The model reveals the effect of the vane tip and the wall boundary layer on fibre orientation distribution. The boundary layer will for both in the plane of paper and in the plane of contraction wider the fibre orientation distributions, i.e the fibres will be less oriented. For the outlet profile of the contraction the fibre orientation distribution will be more effected by the blunt vane tip than the tapered vane tip. The model is validated with experimental results in literature and a good qualitatively agreement was archived.
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| 10. |
- Hyensjö, Marko, et al.
(författare)
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Modelling the effect of shear flow on fibre orientation anisotropy in a planar contraction
- 2007
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 22:3, s. 376-382
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Tidskriftsartikel (refereegranskat)abstract
- The effect of turbulence generating vanes and its location in a planar contraction on fibre orientation anisotropy was studied by mathematical modelling. We use single phase CFD (Computational Fluid Dynamic) modelling as an input for the fibre orientation dispersion model to study the effect of shear flow and turbulence in an accelerated fluid flow on fibre orientation anisotropy. For different streamlines in the contracting channel, the fibre orientation distribution model is solved, and the fibre orientation anisotropy could be studied along streamlines near the vane wall and vane tip and further away downstream. The boundary layer did decrease the fibre orientation anisotropy both in the plane of paper and in the plane of contraction, i.e the fibres were less oriented. For the outlet profile of the contraction the fibre orientation anisotropy was more effected by the blunt vane tip than the tapered one. Experimental results in the literature were used to validate this modelling approach and a good qualitative agreement was achieved.
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