B. Vink, Schot; Toxopeus, S. L.
A Verification and Validation Study of CFD Simulations for the Flow Around A Tug Conference
20th Numerical Towing Tank Symposium (NuTTS), Wageningen, The Netherlands, 2017.
@conference{Vink2017,
title = {A Verification and Validation Study of CFD Simulations for the Flow Around A Tug},
author = {Vink, B., Schot, J., Vaz, G. and Toxopeus, S.L.},
url = {http://www.marin.nl/web/Publications/Publication-items/A-Verification-and-Validation-Study-of-CFD-Simulations-for-the-Flow-Around-A-Tug.htm},
year = {2017},
date = {2017-10-03},
booktitle = {20th Numerical Towing Tank Symposium (NuTTS), Wageningen, The Netherlands},
abstract = {An important vessel for the operational process in a harbour is the tug, a vessel built for the specific purpose of quickly manoeuvring larger vessels in waterways. The key features of a tug are the towing and escorting performances under optimal conditions, which are often reached when sailing under drift at high Froude numbers. Potential users or buyers are comparing tugs on these key features. Thus, for tug designers it is of significant importance to correctly predict the performance of new designs, therewith enabling themselves to verify possible improvements. These predictions, based on lift and drag characteristics of the hull and appendages, are frequently performed using free running or captive model tests, which can be expensive, give no thorough insight in flow specifics and although large-scale models are used still suffer from scale effects. An alternative approach is the use of viscous flow computations, also called Computational Fluid Dynamics (CFD).
This present work will initially estimate the experimental uncertainties from captive model tests to obtain correct validation material. Thereafter a verification and validation exercise of free surface simulations with the KSKL turbulence model and a drift angle of 15 deg will be presented. These are followed by a turbulence sensitivity study of the KSKL, SST, EARSM and DDES turbulence model and finally simulations at other drift angles with the KSKL turbulence will be presented.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
This present work will initially estimate the experimental uncertainties from captive model tests to obtain correct validation material. Thereafter a verification and validation exercise of free surface simulations with the KSKL turbulence model and a drift angle of 15 deg will be presented. These are followed by a turbulence sensitivity study of the KSKL, SST, EARSM and DDES turbulence model and finally simulations at other drift angles with the KSKL turbulence will be presented.
A. Maximiano, Vaz; Scharnke, J.
CFD Verification and Validation Study for a Captive Bullet Entry in Calm Water Conference
OMAE ASME 36th International Conference on Ocean, Offshore and Arctic Engineering, Trondheim, Norway, 2017.
@conference{Maximiano2017,
title = {CFD Verification and Validation Study for a Captive Bullet Entry in Calm Water},
author = {Maximiano, A., Vaz, G. and Scharnke, J.},
url = {http://www.marin.nl/web/Publications/Publication-items/CFD-Verification-and-Validation-Study-for-a-Captive-Bullet-Entry-in-Calm-Water.htm},
year = {2017},
date = {2017-06-25},
booktitle = {OMAE ASME 36th International Conference on Ocean, Offshore and Arctic Engineering, Trondheim, Norway},
pages = {OMAE2017-61666},
abstract = {As a step towards complex impact loads cases, e.g. lifeboat drop tests or ship/platform slamming in waves, a verification and validation (V&V) study is carried out with an open-usage community based CFD code ReFRESCO for a simple impact load test case: a captive axisymmetric generic lifeboat shape (bullet) that penetrates the water surface at a constant velocity and angle of attack. The quantities of interest are the body fixed longitudinal force FX, vertical force FZ, and pitch moment MYY.
The influence of the iterative convergence level, domain size and free surface modelling are investigated. Seven different grids and four time steps were used to assess the grid and time step sensitivity, in a total of 28 calculations. For the tested grids and time steps it was found that the results are more sensitive to the grid resolution than to the time step. The pressure distribution on the hull is correlated with the trends observed in the loads, and the relation between between relative and static pressure is found to be important for the calculated loads. An experimental test campaign was previously carried out by MARIN, and its results are used to validate the simulations performed. A very good match between experiments and simulations is found.
A V&V study is performed for the quantities of interest at nine different time instants covering the impact phase. The numerical uncertainties are obtained from a solution verification procedure [1]. The experimental uncertainties are estimated, and a validation exercise carried out according to the ASME standards [2]. The outcome of the validation exercise is an estimated 95% confidence interval for the modelling error, M. For FX the modelling error is below 15 N, for 8 out of 9 time instants. For FZ the modelling error is below 14 N, except at the time instants where, due to vibrations in the experimental setup, a larger value (up to 23 N) is found. For MYY the modelling error is under 5Nm. These results provide confidence in ReFRESCO for the simulation of free surface impact flows.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
The influence of the iterative convergence level, domain size and free surface modelling are investigated. Seven different grids and four time steps were used to assess the grid and time step sensitivity, in a total of 28 calculations. For the tested grids and time steps it was found that the results are more sensitive to the grid resolution than to the time step. The pressure distribution on the hull is correlated with the trends observed in the loads, and the relation between between relative and static pressure is found to be important for the calculated loads. An experimental test campaign was previously carried out by MARIN, and its results are used to validate the simulations performed. A very good match between experiments and simulations is found.
A V&V study is performed for the quantities of interest at nine different time instants covering the impact phase. The numerical uncertainties are obtained from a solution verification procedure [1]. The experimental uncertainties are estimated, and a validation exercise carried out according to the ASME standards [2]. The outcome of the validation exercise is an estimated 95% confidence interval for the modelling error, M. For FX the modelling error is below 15 N, for 8 out of 9 time instants. For FZ the modelling error is below 14 N, except at the time instants where, due to vibrations in the experimental setup, a larger value (up to 23 N) is found. For MYY the modelling error is under 5Nm. These results provide confidence in ReFRESCO for the simulation of free surface impact flows.
M. Kerkvliet, Carette; Straten, O. van
Analysis of free surface anti-roll tank using URANS. Verification and validation Conference
13th International Symposium on Practical Design of Ships (PRADS), Copenhagen, Denmark, 2016.
@conference{Kerkvliet2016,
title = {Analysis of free surface anti-roll tank using URANS. Verification and validation},
author = {Kerkvliet, M., Carette, N. and Straten, O. van},
url = {http://www.marin.nl/web/Publications/Papers/Analysis-of-free-surface-antiroll-tank-using-URANS.-Verification-and-validation-1.htm},
year = {2016},
date = {2016-09-04},
booktitle = {13th International Symposium on Practical Design of Ships (PRADS), Copenhagen, Denmark},
pages = {ID055},
abstract = {To prevent excessive roll motion of ships operating in seas, damping systems are often required. Exterior systems can be used like, bilge keels or active stabilizer fins, or interior systems like anti-roll tanks (ARTs). There are mainly two sorts of ARTs, i.e. free surface tanks and Utype tanks. Both types have been studied extensively in the past, e.g. by Watts (1883), Frahm (1911) and Verhagen and Wijngaarden (1965), but also more recently, e.g. by Lee and Vassalos (1996), Kerkvliet et al. (2014) and Carette (2015). The content of this paper is restricted to the free surface type ART, which is nowadays often used to increase the roll damping of ships passively. The main advantages of such an ART are the large damping moment at small roll amplitudes and the ease to adapt the response by changing the water level. The response of the tank is highly frequency and amplitude dependent with a strong non-linear character (Carette et al., 2016). Also the shape of the interior geometry, e.g. additional struts, plates or other flow obstructions, will have an effect on the response, which makes it difficult to predict the response by analytical models. Therefore, systematic oscillation tests are often performed by model-scale experiments or by use of Computational Fluid Dynamics (CFD). This paper shows the response of a two-dimensional (2D) and three-dimensional (3D) model-scale free surface ART using the CFD code ReFRESCO (www.refresco.org). The objective of this paper is to show which issues are important when CFD is used as a research and design tool. A verification and validation study is performed to determine numerical settings to obtain a good trade-off between accuracy and computational costs. The CFD results are validated against model-scale experimental results, based on the work of Carette (2015). The results show that CFD can be used as a simulation driven design tool to accurately predict the response of an ART.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
2017
B. Vink, Schot; Toxopeus, S. L.
A Verification and Validation Study of CFD Simulations for the Flow Around A Tug Conference
20th Numerical Towing Tank Symposium (NuTTS), Wageningen, The Netherlands, 2017.
Abstract | Links | BibTeX | Tags: CFD, tugs, verification and validation
@conference{Vink2017,
title = {A Verification and Validation Study of CFD Simulations for the Flow Around A Tug},
author = {Vink, B., Schot, J., Vaz, G. and Toxopeus, S.L.},
url = {http://www.marin.nl/web/Publications/Publication-items/A-Verification-and-Validation-Study-of-CFD-Simulations-for-the-Flow-Around-A-Tug.htm},
year = {2017},
date = {2017-10-03},
booktitle = {20th Numerical Towing Tank Symposium (NuTTS), Wageningen, The Netherlands},
abstract = {An important vessel for the operational process in a harbour is the tug, a vessel built for the specific purpose of quickly manoeuvring larger vessels in waterways. The key features of a tug are the towing and escorting performances under optimal conditions, which are often reached when sailing under drift at high Froude numbers. Potential users or buyers are comparing tugs on these key features. Thus, for tug designers it is of significant importance to correctly predict the performance of new designs, therewith enabling themselves to verify possible improvements. These predictions, based on lift and drag characteristics of the hull and appendages, are frequently performed using free running or captive model tests, which can be expensive, give no thorough insight in flow specifics and although large-scale models are used still suffer from scale effects. An alternative approach is the use of viscous flow computations, also called Computational Fluid Dynamics (CFD).
This present work will initially estimate the experimental uncertainties from captive model tests to obtain correct validation material. Thereafter a verification and validation exercise of free surface simulations with the KSKL turbulence model and a drift angle of 15 deg will be presented. These are followed by a turbulence sensitivity study of the KSKL, SST, EARSM and DDES turbulence model and finally simulations at other drift angles with the KSKL turbulence will be presented.},
keywords = {CFD, tugs, verification and validation},
pubstate = {published},
tppubtype = {conference}
}
This present work will initially estimate the experimental uncertainties from captive model tests to obtain correct validation material. Thereafter a verification and validation exercise of free surface simulations with the KSKL turbulence model and a drift angle of 15 deg will be presented. These are followed by a turbulence sensitivity study of the KSKL, SST, EARSM and DDES turbulence model and finally simulations at other drift angles with the KSKL turbulence will be presented.
A. Maximiano, Vaz; Scharnke, J.
CFD Verification and Validation Study for a Captive Bullet Entry in Calm Water Conference
OMAE ASME 36th International Conference on Ocean, Offshore and Arctic Engineering, Trondheim, Norway, 2017.
Abstract | Links | BibTeX | Tags: CFD, ReFRESCO, verification and validation
@conference{Maximiano2017,
title = {CFD Verification and Validation Study for a Captive Bullet Entry in Calm Water},
author = {Maximiano, A., Vaz, G. and Scharnke, J.},
url = {http://www.marin.nl/web/Publications/Publication-items/CFD-Verification-and-Validation-Study-for-a-Captive-Bullet-Entry-in-Calm-Water.htm},
year = {2017},
date = {2017-06-25},
booktitle = {OMAE ASME 36th International Conference on Ocean, Offshore and Arctic Engineering, Trondheim, Norway},
pages = {OMAE2017-61666},
abstract = {As a step towards complex impact loads cases, e.g. lifeboat drop tests or ship/platform slamming in waves, a verification and validation (V&V) study is carried out with an open-usage community based CFD code ReFRESCO for a simple impact load test case: a captive axisymmetric generic lifeboat shape (bullet) that penetrates the water surface at a constant velocity and angle of attack. The quantities of interest are the body fixed longitudinal force FX, vertical force FZ, and pitch moment MYY.
The influence of the iterative convergence level, domain size and free surface modelling are investigated. Seven different grids and four time steps were used to assess the grid and time step sensitivity, in a total of 28 calculations. For the tested grids and time steps it was found that the results are more sensitive to the grid resolution than to the time step. The pressure distribution on the hull is correlated with the trends observed in the loads, and the relation between between relative and static pressure is found to be important for the calculated loads. An experimental test campaign was previously carried out by MARIN, and its results are used to validate the simulations performed. A very good match between experiments and simulations is found.
A V&V study is performed for the quantities of interest at nine different time instants covering the impact phase. The numerical uncertainties are obtained from a solution verification procedure [1]. The experimental uncertainties are estimated, and a validation exercise carried out according to the ASME standards [2]. The outcome of the validation exercise is an estimated 95% confidence interval for the modelling error, M. For FX the modelling error is below 15 N, for 8 out of 9 time instants. For FZ the modelling error is below 14 N, except at the time instants where, due to vibrations in the experimental setup, a larger value (up to 23 N) is found. For MYY the modelling error is under 5Nm. These results provide confidence in ReFRESCO for the simulation of free surface impact flows.},
keywords = {CFD, ReFRESCO, verification and validation},
pubstate = {published},
tppubtype = {conference}
}
The influence of the iterative convergence level, domain size and free surface modelling are investigated. Seven different grids and four time steps were used to assess the grid and time step sensitivity, in a total of 28 calculations. For the tested grids and time steps it was found that the results are more sensitive to the grid resolution than to the time step. The pressure distribution on the hull is correlated with the trends observed in the loads, and the relation between between relative and static pressure is found to be important for the calculated loads. An experimental test campaign was previously carried out by MARIN, and its results are used to validate the simulations performed. A very good match between experiments and simulations is found.
A V&V study is performed for the quantities of interest at nine different time instants covering the impact phase. The numerical uncertainties are obtained from a solution verification procedure [1]. The experimental uncertainties are estimated, and a validation exercise carried out according to the ASME standards [2]. The outcome of the validation exercise is an estimated 95% confidence interval for the modelling error, M. For FX the modelling error is below 15 N, for 8 out of 9 time instants. For FZ the modelling error is below 14 N, except at the time instants where, due to vibrations in the experimental setup, a larger value (up to 23 N) is found. For MYY the modelling error is under 5Nm. These results provide confidence in ReFRESCO for the simulation of free surface impact flows.
2016
M. Kerkvliet, Carette; Straten, O. van
Analysis of free surface anti-roll tank using URANS. Verification and validation Conference
13th International Symposium on Practical Design of Ships (PRADS), Copenhagen, Denmark, 2016.
Abstract | Links | BibTeX | Tags: anti-roll tank, ART, CFD, free surface, ReFRESCO, URANS, verification and validation
@conference{Kerkvliet2016,
title = {Analysis of free surface anti-roll tank using URANS. Verification and validation},
author = {Kerkvliet, M., Carette, N. and Straten, O. van},
url = {http://www.marin.nl/web/Publications/Papers/Analysis-of-free-surface-antiroll-tank-using-URANS.-Verification-and-validation-1.htm},
year = {2016},
date = {2016-09-04},
booktitle = {13th International Symposium on Practical Design of Ships (PRADS), Copenhagen, Denmark},
pages = {ID055},
abstract = {To prevent excessive roll motion of ships operating in seas, damping systems are often required. Exterior systems can be used like, bilge keels or active stabilizer fins, or interior systems like anti-roll tanks (ARTs). There are mainly two sorts of ARTs, i.e. free surface tanks and Utype tanks. Both types have been studied extensively in the past, e.g. by Watts (1883), Frahm (1911) and Verhagen and Wijngaarden (1965), but also more recently, e.g. by Lee and Vassalos (1996), Kerkvliet et al. (2014) and Carette (2015). The content of this paper is restricted to the free surface type ART, which is nowadays often used to increase the roll damping of ships passively. The main advantages of such an ART are the large damping moment at small roll amplitudes and the ease to adapt the response by changing the water level. The response of the tank is highly frequency and amplitude dependent with a strong non-linear character (Carette et al., 2016). Also the shape of the interior geometry, e.g. additional struts, plates or other flow obstructions, will have an effect on the response, which makes it difficult to predict the response by analytical models. Therefore, systematic oscillation tests are often performed by model-scale experiments or by use of Computational Fluid Dynamics (CFD). This paper shows the response of a two-dimensional (2D) and three-dimensional (3D) model-scale free surface ART using the CFD code ReFRESCO (www.refresco.org). The objective of this paper is to show which issues are important when CFD is used as a research and design tool. A verification and validation study is performed to determine numerical settings to obtain a good trade-off between accuracy and computational costs. The CFD results are validated against model-scale experimental results, based on the work of Carette (2015). The results show that CFD can be used as a simulation driven design tool to accurately predict the response of an ART.},
keywords = {anti-roll tank, ART, CFD, free surface, ReFRESCO, URANS, verification and validation},
pubstate = {published},
tppubtype = {conference}
}