1.
L. Eça, Vaz; Abreu, H.
OMAE ASME 36th International Conference on Ocean, Offshore and Arctic Engineering, Trondheim, Norway, 2017.
@conference{Eça2017b,
title = {Validation Exercises for the Calculation of the Flow Around a Squared Column With Rounded Corners at High Reynolds Numbers With the RANS Equations},
author = {Eça, L., Vaz, G., Koop, A.K., Pereira, F. and Abreu, H.},
url = {http://www.marin.nl/web/Publications/Publication-items/Validation-Exercises-for-the-Calculation-of-the-Flow-Around-a-Squared-Column-With-Rounded-Corners-at-High-Reynolds-Numbers-With-the-RANS-Equations.htm},
year = {2017},
date = {2017-06-25},
booktitle = {OMAE ASME 36th International Conference on Ocean, Offshore and Arctic Engineering, Trondheim, Norway},
pages = {OMAE2017-61937},
abstract = {This paper presents Validation studies, i.e. evaluation of the modelling error, for the ensemble averaged Navier-Stokes (RANS) equations supplemented by eddy-viscosity models (SST k-omega and Spalart & Allmaras). The selected test case is the flow around a squared column with rounded corners at Reynolds number ranging from 1E5 to 1E7. Selected flow quantities include time-averaged quantities of drag and lift coefficients, base pressure coefficient, Strouhal number and the standard deviation of the lift coefficient. For this latter quantity, ensemble (phase) averaging must also be applied to the experimental data to obtain quantities with the same physical meaning, as illustrated in this work.
Even for the simple assumption of two-dimensional flow of the present simulations, the level of grid refinement and iterative convergence criteria required to obtain acceptable numerical uncertainties is more demanding than those typically observed in the open literature. However, the most important result obtained in this study is that the use of turbulence models developed for statistically steady flows may lead to flow fields that physically are at least questionable. From the three Reynolds numbers tested using three eddy-viscosity models, statistically periodic solutions with zero lift were only obtained with the SST k-omega at Re = 1E5. However, in that case, it is possible to numerically (including statistical, iterative and discretization errors) converge two different flow fields for the same space boundary conditions, but different solution strategies (start up of the vortex shedding).},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
This paper presents Validation studies, i.e. evaluation of the modelling error, for the ensemble averaged Navier-Stokes (RANS) equations supplemented by eddy-viscosity models (SST k-omega and Spalart & Allmaras). The selected test case is the flow around a squared column with rounded corners at Reynolds number ranging from 1E5 to 1E7. Selected flow quantities include time-averaged quantities of drag and lift coefficients, base pressure coefficient, Strouhal number and the standard deviation of the lift coefficient. For this latter quantity, ensemble (phase) averaging must also be applied to the experimental data to obtain quantities with the same physical meaning, as illustrated in this work.
Even for the simple assumption of two-dimensional flow of the present simulations, the level of grid refinement and iterative convergence criteria required to obtain acceptable numerical uncertainties is more demanding than those typically observed in the open literature. However, the most important result obtained in this study is that the use of turbulence models developed for statistically steady flows may lead to flow fields that physically are at least questionable. From the three Reynolds numbers tested using three eddy-viscosity models, statistically periodic solutions with zero lift were only obtained with the SST k-omega at Re = 1E5. However, in that case, it is possible to numerically (including statistical, iterative and discretization errors) converge two different flow fields for the same space boundary conditions, but different solution strategies (start up of the vortex shedding).
Even for the simple assumption of two-dimensional flow of the present simulations, the level of grid refinement and iterative convergence criteria required to obtain acceptable numerical uncertainties is more demanding than those typically observed in the open literature. However, the most important result obtained in this study is that the use of turbulence models developed for statistically steady flows may lead to flow fields that physically are at least questionable. From the three Reynolds numbers tested using three eddy-viscosity models, statistically periodic solutions with zero lift were only obtained with the SST k-omega at Re = 1E5. However, in that case, it is possible to numerically (including statistical, iterative and discretization errors) converge two different flow fields for the same space boundary conditions, but different solution strategies (start up of the vortex shedding).
2.
J. Baltazar, Rijpkema; Falcão de Campos, J. A. C.
Fifth International Symposium on Marine Propulsors (SMP), Espoo, Finland, 2017.
@conference{Baltazar2017,
title = {On the Use of the γ−Re˜ θ Transition Model for the Prediction of the Propeller Performance at Model-Scale},
author = {Baltazar, J., Rijpkema, D. and Falcão de Campos, J.A.C.},
url = {http://www.marin.nl/web/Publications/Publication-items/On-the-Use-of-the-gReth-Transition-Model-for-the-Prediction-of-the-Propeller-Performance-at-ModelScale.htm},
year = {2017},
date = {2017-06-01},
booktitle = {Fifth International Symposium on Marine Propulsors (SMP), Espoo, Finland},
abstract = {The goal of the present work is to improve the prediction of propeller performance at model-scale using a local correlation transition model. Results are presented for two marine propellers for which paint-tests have been conducted and experimental open-water data is available. The numerical results using the k − ω SST turbulence model and the γ − Re˜ θ transition model are compared with the experiments. In order to distinguish between numerical and modelling errors in the comparison with experimental results, a verification study using a range of geometrically similar grids with different grid densities is made. The influence of the turbulence inlet quantities on the numerical results is discussed and boundary-layer characteristics are presented. Finally, the numerical predictions are compared with the experimental results. An improvement in the flow pattern is achieved with the transition model. However, the model strongly depends on the turbulence inlet quantities for the prediction of the transition location. Both propellers show an increase in thrust of 2% to 4% and similar torque when using the transition model.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
The goal of the present work is to improve the prediction of propeller performance at model-scale using a local correlation transition model. Results are presented for two marine propellers for which paint-tests have been conducted and experimental open-water data is available. The numerical results using the k − ω SST turbulence model and the γ − Re˜ θ transition model are compared with the experiments. In order to distinguish between numerical and modelling errors in the comparison with experimental results, a verification study using a range of geometrically similar grids with different grid densities is made. The influence of the turbulence inlet quantities on the numerical results is discussed and boundary-layer characteristics are presented. Finally, the numerical predictions are compared with the experimental results. An improvement in the flow pattern is achieved with the transition model. However, the model strongly depends on the turbulence inlet quantities for the prediction of the transition location. Both propellers show an increase in thrust of 2% to 4% and similar torque when using the transition model.
2017
L. Eça, Vaz; Abreu, H.
OMAE ASME 36th International Conference on Ocean, Offshore and Arctic Engineering, Trondheim, Norway, 2017.
Abstract | Links | BibTeX | Tags: Calculation, RANS Equations, Validation studies
@conference{Eça2017b,
title = {Validation Exercises for the Calculation of the Flow Around a Squared Column With Rounded Corners at High Reynolds Numbers With the RANS Equations},
author = {Eça, L., Vaz, G., Koop, A.K., Pereira, F. and Abreu, H.},
url = {http://www.marin.nl/web/Publications/Publication-items/Validation-Exercises-for-the-Calculation-of-the-Flow-Around-a-Squared-Column-With-Rounded-Corners-at-High-Reynolds-Numbers-With-the-RANS-Equations.htm},
year = {2017},
date = {2017-06-25},
booktitle = {OMAE ASME 36th International Conference on Ocean, Offshore and Arctic Engineering, Trondheim, Norway},
pages = {OMAE2017-61937},
abstract = {This paper presents Validation studies, i.e. evaluation of the modelling error, for the ensemble averaged Navier-Stokes (RANS) equations supplemented by eddy-viscosity models (SST k-omega and Spalart & Allmaras). The selected test case is the flow around a squared column with rounded corners at Reynolds number ranging from 1E5 to 1E7. Selected flow quantities include time-averaged quantities of drag and lift coefficients, base pressure coefficient, Strouhal number and the standard deviation of the lift coefficient. For this latter quantity, ensemble (phase) averaging must also be applied to the experimental data to obtain quantities with the same physical meaning, as illustrated in this work.
Even for the simple assumption of two-dimensional flow of the present simulations, the level of grid refinement and iterative convergence criteria required to obtain acceptable numerical uncertainties is more demanding than those typically observed in the open literature. However, the most important result obtained in this study is that the use of turbulence models developed for statistically steady flows may lead to flow fields that physically are at least questionable. From the three Reynolds numbers tested using three eddy-viscosity models, statistically periodic solutions with zero lift were only obtained with the SST k-omega at Re = 1E5. However, in that case, it is possible to numerically (including statistical, iterative and discretization errors) converge two different flow fields for the same space boundary conditions, but different solution strategies (start up of the vortex shedding).},
keywords = {Calculation, RANS Equations, Validation studies},
pubstate = {published},
tppubtype = {conference}
}
This paper presents Validation studies, i.e. evaluation of the modelling error, for the ensemble averaged Navier-Stokes (RANS) equations supplemented by eddy-viscosity models (SST k-omega and Spalart & Allmaras). The selected test case is the flow around a squared column with rounded corners at Reynolds number ranging from 1E5 to 1E7. Selected flow quantities include time-averaged quantities of drag and lift coefficients, base pressure coefficient, Strouhal number and the standard deviation of the lift coefficient. For this latter quantity, ensemble (phase) averaging must also be applied to the experimental data to obtain quantities with the same physical meaning, as illustrated in this work.
Even for the simple assumption of two-dimensional flow of the present simulations, the level of grid refinement and iterative convergence criteria required to obtain acceptable numerical uncertainties is more demanding than those typically observed in the open literature. However, the most important result obtained in this study is that the use of turbulence models developed for statistically steady flows may lead to flow fields that physically are at least questionable. From the three Reynolds numbers tested using three eddy-viscosity models, statistically periodic solutions with zero lift were only obtained with the SST k-omega at Re = 1E5. However, in that case, it is possible to numerically (including statistical, iterative and discretization errors) converge two different flow fields for the same space boundary conditions, but different solution strategies (start up of the vortex shedding).
Even for the simple assumption of two-dimensional flow of the present simulations, the level of grid refinement and iterative convergence criteria required to obtain acceptable numerical uncertainties is more demanding than those typically observed in the open literature. However, the most important result obtained in this study is that the use of turbulence models developed for statistically steady flows may lead to flow fields that physically are at least questionable. From the three Reynolds numbers tested using three eddy-viscosity models, statistically periodic solutions with zero lift were only obtained with the SST k-omega at Re = 1E5. However, in that case, it is possible to numerically (including statistical, iterative and discretization errors) converge two different flow fields for the same space boundary conditions, but different solution strategies (start up of the vortex shedding).
J. Baltazar, Rijpkema; Falcão de Campos, J. A. C.
Fifth International Symposium on Marine Propulsors (SMP), Espoo, Finland, 2017.
Abstract | Links | BibTeX | Tags: Marine Propeller, RANS Equations, Transitional Flow, Turbulence and Transition Models.
@conference{Baltazar2017,
title = {On the Use of the γ−Re˜ θ Transition Model for the Prediction of the Propeller Performance at Model-Scale},
author = {Baltazar, J., Rijpkema, D. and Falcão de Campos, J.A.C.},
url = {http://www.marin.nl/web/Publications/Publication-items/On-the-Use-of-the-gReth-Transition-Model-for-the-Prediction-of-the-Propeller-Performance-at-ModelScale.htm},
year = {2017},
date = {2017-06-01},
booktitle = {Fifth International Symposium on Marine Propulsors (SMP), Espoo, Finland},
abstract = {The goal of the present work is to improve the prediction of propeller performance at model-scale using a local correlation transition model. Results are presented for two marine propellers for which paint-tests have been conducted and experimental open-water data is available. The numerical results using the k − ω SST turbulence model and the γ − Re˜ θ transition model are compared with the experiments. In order to distinguish between numerical and modelling errors in the comparison with experimental results, a verification study using a range of geometrically similar grids with different grid densities is made. The influence of the turbulence inlet quantities on the numerical results is discussed and boundary-layer characteristics are presented. Finally, the numerical predictions are compared with the experimental results. An improvement in the flow pattern is achieved with the transition model. However, the model strongly depends on the turbulence inlet quantities for the prediction of the transition location. Both propellers show an increase in thrust of 2% to 4% and similar torque when using the transition model.},
keywords = {Marine Propeller, RANS Equations, Transitional Flow, Turbulence and Transition Models.},
pubstate = {published},
tppubtype = {conference}
}
The goal of the present work is to improve the prediction of propeller performance at model-scale using a local correlation transition model. Results are presented for two marine propellers for which paint-tests have been conducted and experimental open-water data is available. The numerical results using the k − ω SST turbulence model and the γ − Re˜ θ transition model are compared with the experiments. In order to distinguish between numerical and modelling errors in the comparison with experimental results, a verification study using a range of geometrically similar grids with different grid densities is made. The influence of the turbulence inlet quantities on the numerical results is discussed and boundary-layer characteristics are presented. Finally, the numerical predictions are compared with the experimental results. An improvement in the flow pattern is achieved with the transition model. However, the model strongly depends on the turbulence inlet quantities for the prediction of the transition location. Both propellers show an increase in thrust of 2% to 4% and similar torque when using the transition model.