1,721,386 research outputs found
[Retrato ecuestre de Felipe V] [Material gráfico] / I Bap. "Ravanals F. Matriti 1708
No full textEstampa suelta de: Glorias de el Señor D. Felipe Quinto, rey de las Españas y emperador del nuevo mundo ... y fatales consequencias ... / predicado por ... Fr. Antonio Cabrera ... ; sale a luz a instancias ... del señor ... Bartolome Ruiz Contreras ... -- En Madrid : por Francisco Antonio de Villa-Diego, 170
Improving model scale propeller performance prediction using the k - kL - ω transition model in OpenFOAM
No full textThe effect of laminar to turbulent flow transition plays an important role for the prediction of model scale performance, which is of utmost interest for the development of scaling approaches entirely based on Computational Fluid Dynamics calculations. The recent inclusion of transition models (either based on local correlations, like the γ - Re θ, or on the concept of kinetic laminar energy, like the k - k L - ω) in many RANS codes fosters their application for improving the model scale prediction of propeller performance. In the present work the numerical results using the well-established SST k - ω and the k - k L - ω turbulence models available in OpenFOAM are presented and compared with towing tank experiments for three test case propellers. The influence of turbulence parameters (i.e. turbulence intensity and turbulent viscosity ratio at inlet) is discussed, at first for the ERCOFTAC T3A flat plate validation case, through which useful guidelines for propeller performance predictions using transition sensitive turbulence models are derived. By using these relationships, a significant improvement of numerical predictions of propeller forces is achieved, with discrepancies with respect to model scale measurements appreciably reduced if compared to usual fully turbulent calculations. At the same time the limitations of the adopted transitional model are discussed based on the systematic analyses carried out for three test cases
Steady cavitating propeller performance by using OpenFOAM, StarCCM+ and a boundary element method
No full textAccurate and reliable numerical predictions of propeller performance are a fundamental aspect for any analysis and design of a modern propeller. Prediction of cavitation and of cavity extension is another important task, since cavitation is one of the crucial aspects that influences efficiency in addition to propagated noise and blade vibration and erosion. The validation of the numerical tools that support the design process, including open-source codes, is, consequently, essential. The public availability of measurements and observations which cover not only usual thrust and torque in open water conditions (including cavitation) but also unsteady functioning with pressure pulse measurements in the case of
the Potsdam Propeller Test Case certainly represents an extremely useful source of information and an excellent chance for verification and validation purposes. In the present work, the prediction of the Potsdam Propeller Test Case propeller performance using the OpenFOAM computational fluid dynamics package is proposed. After a preliminary validation and calibration of the OpenFOAM native Schnerr–Sauer interphase mass transfer model for cavitating flow, based on the experimental results on a 2D NACA66Mod hydrofoil, open water propeller performance and cavitation predictions are carried out. The OpenFOAM results are finally compared both with the available experimental measurements and with calculations carried out with StarCCM+and with a proprietary boundary element method code, in order to assess
the accuracy and the overall capabilities of the open-source tools (from meshing to post-processing) available in the OpenFOAM package. The comparison, in addition to assessing the accuracy of the open-source approach, is aimed to verify its advantages and drawbacks with respect to widely used solvers and to further verify the reliability of traditional boundary element method approaches that are still widely adopted for design and optimization (thanks to their extremely higher computational efficiency) in a very demanding test case
Investigation on Nonlinear and Viscous Effects in Ship Motion Evaluated by CFD Methodologies
No full text
CFD Prediction of the Asymmetrical Shaft Unbalance During Ship Maneuvers
No full textAbstract. The paper explores the accuracy of a low-cost CFD based approach to
evaluate the propeller load variation experienced during manoeuvring conditions.
The proposed procedure is based on the inclusion, in the ship hydrodynamic analyses by RANS, of the propeller effect through a body-force approach calibrated on
BEM calculation to realize a computationally efficient method. Numerical results
have been compared with the literature available experimental data performed on
the well-known DTMB5415 benchmark test case, where the thrusts experienced by
both of her propellers during dedicated Captive Model Tests were recorded. Both
pure drift and pure yaw tests have been considered in the numerical campaign to
cover the entire kinematic conditions involved during standard IMO manoeuvres.
To prove the effectiveness of the method, also a severe turning circle condition
is evaluated. The comparison shows the maturity of these numerical calculations,
even if based on a simplified approach, to correctly evaluate the propeller unbalance, opening the way to the application of the proposed method to investigate the
causes of load variations in manoeuvre conditions and directly in manoeuvre simulations
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