Ana Lu´ısa Rocha, Lu´ıs E¸ca; Vaz, Guilherme
VII International Conference on Computational Methods in Marine Engineering, 2017.
@conference{Rocha2017,
title = {ON THE NUMERICAL CONVERGENCE PROPERTIES OF THE CALCULATION OF THE FLOW AROUND THE KVLCC2 TANKER IN UNSTRUCTURED GRIDS},
author = {Ana Lu´ısa Rocha, Lu´ıs E¸ca and Guilherme Vaz},
url = {http://www.marin.nl/web/Publications/Publication-items/On-The-Numerical-Convergence-Properties-Of-The-Calculation-Of-The-Flow-Around-The-KVLCC2-Tanker-In-Unstructured-Grids.htm},
year = {2017},
date = {2017-05-01},
booktitle = {VII International Conference on Computational Methods in Marine Engineering},
abstract = {This paper addresses the estimation of numerical errors in the calculation of the flow around the KVLCC2 tanker at model scale Reynolds number in unstructured grids. The flow solution is based on the Reynolds-Averaged Navier-Stokes equations supplemented by the k − ω SST two-equation eddy-viscosity model using the so-called double-body approach, i.e. free surface effects are neglected. Grid refinement studies are performed for sets of grids generated with the open source code SnappyHexMesh and with the HEXPRESSTM grid generator. Definition of grid refinement ratio in unstructured grids and its consequences for the estimation of numerical errors is discussed. Friction and pressure resistance coefficients and mean velocity components at the propeller plane are compared with reference solutions obtained in nearly-orthogonal multi-block structured grids with the same flow solver ReFRESCO.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
F.S. Pereira, Eça; Vaz, G.
Verification and Validation exercises for the flow around the KVLCC2 tanker at model and full-scale Reynolds numbers Journal Article
In: Ocean Engineering, vol. 129, no. DOI: 10.1016/j.oceaneng.2016.11.005, pp. 133-148, 2017.
@article{Pereira2017,
title = {Verification and Validation exercises for the flow around the KVLCC2 tanker at model and full-scale Reynolds numbers},
author = {Pereira, F.S., Eça, L. and Vaz, G.},
url = {http://www.marin.nl/web/Publications/Publication-items/Verification-and-Validation-exercises-for-the-flow-around-the-KVLCC2-tanker-at-model-and-fullscale-Reynolds-numbers.htm},
year = {2017},
date = {2017-01-02},
booktitle = {Ocean Engineering},
journal = {Ocean Engineering},
volume = {129},
number = {DOI: 10.1016/j.oceaneng.2016.11.005},
pages = {133-148},
abstract = {This paper presents the quantification of numerical and modelling errors for the solution of the flow around the KVLCC2 tanker at model-scale Reynolds number. Numerical errors are also quantified for full-scale Reynolds number simulations to address the numerical accuracy of the prediction of scale-effects. The calculations are performed with the solver ReFRESCO using fourteen distinct Reynolds-Averaged Navier-Stokes (RANS) equations models. The quantities of interest for the Validation exercises at model-scale are the resistance coefficient and the velocity and turbulence kinetic energy fields at the propeller plane. Modelling errors are estimated using the ASME V & V20 procedure which requires numerical and experimental data with their respective uncertainties. Numerical uncertainties are dominated by the contribution of the discretization error, which is determined by grid refinement studies. Scale-effects are also assessed for the wake-fraction and formfactor. The outcome shows that quantifying modelling errors is not a trivial exercise that depends on the quality and details of simulations and experiments. Nonetheless, it is also evident that a quantitative evaluation of modelling errors is more reliable than traditional graphical comparisons of simulations and experiments. Fullscale results show scale-effects larger than numerical uncertainties that are illustrated for the form-factor and wake-fraction.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
L. Eça, Klaij; Pereira, F. S.
On code verification of RANS solvers Journal Article
In: Journal of Computational Physics, 2016, vol. 310, pp. 418-439, 2016.
@article{Eça2016b,
title = {On code verification of RANS solvers},
author = {Eça, L., Klaij, C.M., Vaz, G., Hoekstra, M. and Pereira, F.S.},
url = {http://www.marin.nl/web/Publications/Papers/On-code-verification-of-RANS-solvers.htm},
doi = {10.1016/j.jcp.2016.01.002},
year = {2016},
date = {2016-04-01},
journal = {Journal of Computational Physics, 2016},
volume = {310},
pages = {418-439},
abstract = {This article discusses Code Verification of Reynolds-Averaged Navier Stokes (RANS) solvers that rely on face based finite volume discretizations for volumes of arbitrary shape. The study includes test cases with known analytical solutions (generated with the method of manufactured solutions) corresponding to laminar and turbulent flow, with the latter using eddy-viscosity turbulence models. The procedure to perform Code Verification based on grid refinement studies is discussed and the requirements for its correct application are illustrated in a simple one-dimensional problem. It is shown that geometrically similar grids are recommended for proper Code Verification and so the data should not have scatter making the use of least square fits unnecessary. Results show that it may be advantageous to determine the extrapolated error to cell size/time step zero instead of assuming that it is zero, especially when it is hard to determine the asymptotic order of grid convergence. In the RANS examples, several of the features of the ReFRESCO solver are checked including the effects of the available turbulence models in the convergence properties of the code. It is shown that it is required to account for non-orthogonality effects in the discretization of the diffusion terms and that the turbulence quantities transport equations can deteriorate the order of grid convergence of mean flow quantities.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2017
Ana Lu´ısa Rocha, Lu´ıs E¸ca; Vaz, Guilherme
VII International Conference on Computational Methods in Marine Engineering, 2017.
Abstract | Links | BibTeX | Tags: KVLCC2, Numerical Error, RANS, Unstructured Grids
@conference{Rocha2017,
title = {ON THE NUMERICAL CONVERGENCE PROPERTIES OF THE CALCULATION OF THE FLOW AROUND THE KVLCC2 TANKER IN UNSTRUCTURED GRIDS},
author = {Ana Lu´ısa Rocha, Lu´ıs E¸ca and Guilherme Vaz},
url = {http://www.marin.nl/web/Publications/Publication-items/On-The-Numerical-Convergence-Properties-Of-The-Calculation-Of-The-Flow-Around-The-KVLCC2-Tanker-In-Unstructured-Grids.htm},
year = {2017},
date = {2017-05-01},
booktitle = {VII International Conference on Computational Methods in Marine Engineering},
abstract = {This paper addresses the estimation of numerical errors in the calculation of the flow around the KVLCC2 tanker at model scale Reynolds number in unstructured grids. The flow solution is based on the Reynolds-Averaged Navier-Stokes equations supplemented by the k − ω SST two-equation eddy-viscosity model using the so-called double-body approach, i.e. free surface effects are neglected. Grid refinement studies are performed for sets of grids generated with the open source code SnappyHexMesh and with the HEXPRESSTM grid generator. Definition of grid refinement ratio in unstructured grids and its consequences for the estimation of numerical errors is discussed. Friction and pressure resistance coefficients and mean velocity components at the propeller plane are compared with reference solutions obtained in nearly-orthogonal multi-block structured grids with the same flow solver ReFRESCO.},
keywords = {KVLCC2, Numerical Error, RANS, Unstructured Grids},
pubstate = {published},
tppubtype = {conference}
}
F.S. Pereira, Eça; Vaz, G.
Verification and Validation exercises for the flow around the KVLCC2 tanker at model and full-scale Reynolds numbers Journal Article
In: Ocean Engineering, vol. 129, no. DOI: 10.1016/j.oceaneng.2016.11.005, pp. 133-148, 2017.
Abstract | Links | BibTeX | Tags: KVLCC2, Modelling error, Numerical Error, RANS, Turbulence modelling
@article{Pereira2017,
title = {Verification and Validation exercises for the flow around the KVLCC2 tanker at model and full-scale Reynolds numbers},
author = {Pereira, F.S., Eça, L. and Vaz, G.},
url = {http://www.marin.nl/web/Publications/Publication-items/Verification-and-Validation-exercises-for-the-flow-around-the-KVLCC2-tanker-at-model-and-fullscale-Reynolds-numbers.htm},
year = {2017},
date = {2017-01-02},
booktitle = {Ocean Engineering},
journal = {Ocean Engineering},
volume = {129},
number = {DOI: 10.1016/j.oceaneng.2016.11.005},
pages = {133-148},
abstract = {This paper presents the quantification of numerical and modelling errors for the solution of the flow around the KVLCC2 tanker at model-scale Reynolds number. Numerical errors are also quantified for full-scale Reynolds number simulations to address the numerical accuracy of the prediction of scale-effects. The calculations are performed with the solver ReFRESCO using fourteen distinct Reynolds-Averaged Navier-Stokes (RANS) equations models. The quantities of interest for the Validation exercises at model-scale are the resistance coefficient and the velocity and turbulence kinetic energy fields at the propeller plane. Modelling errors are estimated using the ASME V & V20 procedure which requires numerical and experimental data with their respective uncertainties. Numerical uncertainties are dominated by the contribution of the discretization error, which is determined by grid refinement studies. Scale-effects are also assessed for the wake-fraction and formfactor. The outcome shows that quantifying modelling errors is not a trivial exercise that depends on the quality and details of simulations and experiments. Nonetheless, it is also evident that a quantitative evaluation of modelling errors is more reliable than traditional graphical comparisons of simulations and experiments. Fullscale results show scale-effects larger than numerical uncertainties that are illustrated for the form-factor and wake-fraction.},
keywords = {KVLCC2, Modelling error, Numerical Error, RANS, Turbulence modelling},
pubstate = {published},
tppubtype = {article}
}
2016
L. Eça, Klaij; Pereira, F. S.
On code verification of RANS solvers Journal Article
In: Journal of Computational Physics, 2016, vol. 310, pp. 418-439, 2016.
Abstract | Links | BibTeX | Tags: Code verification, Manufactured solutions, Numerical Error, Order of grid convergence
@article{Eça2016b,
title = {On code verification of RANS solvers},
author = {Eça, L., Klaij, C.M., Vaz, G., Hoekstra, M. and Pereira, F.S.},
url = {http://www.marin.nl/web/Publications/Papers/On-code-verification-of-RANS-solvers.htm},
doi = {10.1016/j.jcp.2016.01.002},
year = {2016},
date = {2016-04-01},
journal = {Journal of Computational Physics, 2016},
volume = {310},
pages = {418-439},
abstract = {This article discusses Code Verification of Reynolds-Averaged Navier Stokes (RANS) solvers that rely on face based finite volume discretizations for volumes of arbitrary shape. The study includes test cases with known analytical solutions (generated with the method of manufactured solutions) corresponding to laminar and turbulent flow, with the latter using eddy-viscosity turbulence models. The procedure to perform Code Verification based on grid refinement studies is discussed and the requirements for its correct application are illustrated in a simple one-dimensional problem. It is shown that geometrically similar grids are recommended for proper Code Verification and so the data should not have scatter making the use of least square fits unnecessary. Results show that it may be advantageous to determine the extrapolated error to cell size/time step zero instead of assuming that it is zero, especially when it is hard to determine the asymptotic order of grid convergence. In the RANS examples, several of the features of the ReFRESCO solver are checked including the effects of the available turbulence models in the convergence properties of the code. It is shown that it is required to account for non-orthogonality effects in the discretization of the diffusion terms and that the turbulence quantities transport equations can deteriorate the order of grid convergence of mean flow quantities.},
keywords = {Code verification, Manufactured solutions, Numerical Error, Order of grid convergence},
pubstate = {published},
tppubtype = {article}
}