Scipedia

Green*, D.

Zormpa, M.

Vogel, C

XI International Conference on Computational Methods in Marine Engineering
Development and Validation of an Actuator Line
Method for Floating Turbines
Dylan Green1,∗, Markella Zormpa1 and Christopher Vogel1
1 Department of Engineering Science, University of Oxford,
Parks Road, Oxford, OX1 3PJ, UK
*dylan.green@eng.ox.ac.uk
ABSTRACT
The integration of wind energy into the global power
network has proven its capacity to deliver renew-
able and cost-effective energy. However, conventional
fixed-bottom turbines are limited by water depth and
cannot access the vast wind resources found in deeper
waters, estimated to constitute 80% of all practical
wind energy potential (GWEC. 2022). Floating Off-
shore Wind Turbines (FOWTs) can overcome these
challenges but introduce additional complexities and
unsteadiness into the system due to floating platform
motion. Understanding the dynamic wake system
poses a major challenge in FOWT farm optimisation
and requires high-fidelity yet computationally afford-
able models.
Figure 1: Vorticity contour of a model turbine during har-
monic surge.
In this study, an OpenFOAM-based actuator line
method, previously validated for fixed-bottom wind
(Wimshurst et al. 2017) and tidal (Willden et
al. 2023) turbines, is modified to allow for pre-
scribed six-degree-of-freedom motion representative
of a FOWT. Large eddy simulations combined with
the divergence-free synthetic eddy method of Polleto
et al. (2013) are used to reproduce experimental in-
flow turbulence characteristics. The methodology is
validated against open-source experimental datasets
(Fontanella et al. 2021; Fontanella et al. 2024) making
use of harmonic platform motions, allowing for high
interpretability and generalisability of results. Com-
parison of the rotor loads, near wake and far wake be-
haviours demonstrates good agreement. These find-
ings suggest the methodology is suitable for future
investigations, such as the interplay between inflow
turbulence and the platform-motion induced coherent
structures, multi-turbine interactions, and informing
dynamic corrections for lower-fidelity models.
References
GWEC. Global offshore wind report 2022. 2022
A. Wimshurst and R. H. J. Willden. Extracting lift and drag polars from blade-resolved computational fluid
dynamics for use in actuator line modelling of horizontal axis turbines. Wind Energy, 20:815–833, 2017.
R. H. J. Willden, et al. Tidal turbine benchmarking project: Stage I – Steady flow blind predictions. Volume
15, No. NREL/CP-5700-86715. National Renewable Energy Laboratory (NREL), Golden, CO (United States),
2023.
A. Fontanella, I. Bayati, R. Mikkelsen, M. Belloli, and A. Zasso. UNAFLOW: UNsteady Aerodynamics of
FLOating Wind turbines [Data set], 2021.
A. Fontanella, A. Fusetti, F. Menconi, S. Cioni, F. Papi, S. Muggiasca, G. Persico, V. Dossena, A. Bianchini,
and M. Belloli. NETTUNO Experiment 1 – Wake Development in Floating Wind Turbines [Data set], 2024.
R. Poletto, T. Craft, and A. Revell. A new divergence-free synthetic eddy method for the reproduction of inlet
flow conditions for LES. Flow Turbulence Combust, 91:519–539, 2013.


Development and Validation of an Actuator Line Method for Floating Turbines

Tezzele*, M.

XI International Conference on Computational Methods in Marine Engineering
Predictive digital twins of civil engineering structures
and adaptive planning to account for rare events
Marco Tezzele1
1 Department of Mathematics, Emory University, Atlanta, 30322, GA, United States.
e-mail: marco.tezzele@emory.edu
ABSTRACT
A digital twin is a virtualization of a physical asset built upon a set of computational models that dynamically
update to persistently mirror a unique asset of interest throughout its operational lifespan, enabling informed
decisions that realize value.
The talk covers the health monitoring, predictive maintenance, and management planning of civil structures [1],
with a focus on railway bridges. The asset-twin coupled dynamical system is encoded using a probabilis-
tic graphical model which provides a general framework for data assimilation, state estimation, prediction,
planning, and learning while accounting for the associated uncertainty. The time-repeating observations-to-
decisions flow is modeled using a dynamic Bayesian network. Real-time structural health diagnostics are
provided by assimilating sensed data with deep learning models.
The framework is then extended to increase the robustness to rare events of digital twins modeled with graphical
models. We incorporate probabilistic model-checking and linear programming into the Bayesian network to
enable the construction of risk-averse digital twins [2]. The key idea is to model with a random variable the
probability of the asset to transition from one state to another, thus defining a parametric Markov decision
process. We refine the optimal policy at every time step resulting in a better trade off between operational costs
and performances.
We showcase the capabilities of the proposed framework with a structural digital twin of a railway bridge and
an unmanned aerial vehicle and its adaptive mission replanning.
REFERENCES
[1] M. Torzoni, M. Tezzele, S. Mariani, A. Manzoni, and K. Willcox. A digital twin framework for civil
engineering structures. Computer Methods in Applied Mechanics and Engineering, vol. 418, p. 116584,
2024. doi: 10.1016/j.cma.2023.116584
[2] M. Tezzele, S. Carr, U. Topcu, and K. Willcox. Adaptive planning for risk-aware predictive digital twins.
In Physics-based and Data-driven Modeling for Digital Twins, Eds. K. Cherifi and I.V. Gosea, SEMA
SIMAI Springer Series, 2024. arXiv:2407.20490


Predictive digital twins of civil engineering structures and adaptive planning to account for rare events

Brito*, D.

Eça, L.

Baltazar, J.

 
 
XI International Conference on Computational Methods in Marine Engineering 
 
 
Development of a 2D Potential Flow Reduced-Order Numerical Method for the 
Analysis of Forces and Pressure Fields around Multiple Moving Objects or 
Cascades 
 
Duarte M. Brito1,*, Luís R. Eça1 and João M. Baltazar1 
 
1 Department of Mechanical Engineering, 
Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal. 
 
* duarte.brito@tecnico.ulisboa.pt 
 
ABSTRACT 
The hardware and numerical techniques developments 
of recent years have made potential flow simulations 
overlooked. However, these simulations remain 
valuable engineering tools. Their fast solution 
capabilities make them suitable for integration with 
mathematical optimizers, enabling efficient 
preliminary design processes. 
This paper presents a method for the solution of two-
dimensional, unsteady, ideal fluid flows surrounding 
multiple bodies or multiple cascades. The method is 
based on distributions of singularities (Hess and 
Smith, 1967) and it can handle relative movement 
between multiple bodies or cascades. An example with 
a pair of NACA0012 airfoils is present on Fig. 1 
(plunging amplitude: 
ℎ𝑚𝑎𝑥
𝑐
= 1.0, heave-pitch phase Ψ = 90º , St = 0.4, adimensionalized fore-aft distance 
𝑠
𝑐
= 4.0, fore-aft phase  ϕ𝑡 = 90º). In unsteady applications, the circulation is defined by an initial condition 
derived from a steady-state situation, where the starting vortex is positioned far downstream of the multiple 
bodies, as described in Katz and Plotkin (2021). 
Example applications include multiple flapping foils and subsonic axial ventilators. The results are compared 
with experimental data for pitching and plunging (Strangfeld et al., 2024) and theoretical results (Leishman 
and Gordon, 2006). 
References 
J. Hess and A. Smith. Calculation of Potential Flow about Arbitrary Bodies. Progress in Aerospace Sciences, 
8:1–138, 1967. ISSN 0376-0421. doi: https://doi.org/10.1016/0376-0421(67)90003-6. 
J. Katz and A. Plotkin. Low-Speed Aerodynamics. Cambridge University Press, 2nd edition, 2001. 
Leishman, J. Gordon. Principles of Helicopter Aerodynamics. 2nd ed, Cambridge University Press, 2006. 
C. Strangfeld, H.F. Müller-Vahl, C.N. Nayeri, C.O. Paschereit, and D. Greenblatt. Airfoil Synchronous Surging 
and Pitching. 2024. doi: 10.48550/arXiv.2408.10675. 
Figure 1: Coefficients of lift and drag for a pair of 
tandem flapping foils, one upstream (1) and one 
downstream (2). 
 


Development of a 2D Potential Flow Reduced-Order Numerical Method for the Analysis of Forces and Pressure Fields around Multiple Moving Objects or Cascades

Jensen, R.

Yang, J.

Stroh, A.

Frohnapfel, B.

Bagheri, S.

Foroo, P.

XI International Conference on Computational Methods in Marine Engineering
The path from homogeneous to heterogeneous roughness drag models
Rune M. Jensen1, Jiasheng Yang2, Alexander Stroh2, Bettina Frohnapfel2, Shervin Bagheri3 and
Pourya Forooghi1,∗
1 Deptartment of Mechanical & Production Engineering, Aarhus University, 8200 Aarhus, Denmark
2 Institute of Fluid Mechanics (ISTM), Karlsruhe Institute of Tech., 76131 Karlsruhe, Germany
3Division of Fluid Mechanics, KTH Mechanics, Royal Institute of Tech., 100 44 Stockholm, Sweden
∗ forooghi@mpe.au.dk
ABSTRACT
The question of how to determine the skin-friction
drag on an ’arbitrary’ rough surface merely based on
the roughness topography has received a great deal
of attention in the turbulent flow literature. Several
correlations and models have been proposed ranging
from empirical correlations to the recent data-driven
models with multiple inputs (see Chung et al. (2021)
for a comprehensive review).
While roughness in many real-world applications, in-
cluding on ship hulls, is strictly heterogeneous, the
vast majority of existing correlations and models are
developed for homogeneous (and isotropic) rough-
ness. This calls for an extension of the state of the art.
The present contribution is an attempt to discuss the
way ahead based on some recent results. Specifically
we are interested to identify the most suitable set of in-
puts for both homogeneous and heterogeneous rough-
ness models.
We begin with answering the question of what would
be an ideal input into a model for homogeneous
roughness. To this end, we introduce a recent data-
driven model (Yang et al., 2023) trained based on a
wide range of artificially generated irregular rough-
ness samples characeterized using direct numerical
simulation (DNS). The results show that a model with
the discretized PDF and power spectrum of roughness
height as inputs outperforms other forms of reduced
order input in terms of generalizabiliy.
Subsequently, we will discuss the case of heteroge-
neous roughness - specifically patches of roughness
on an otherwise smooth surface - using DNS data
in plane channels. Here the roughness topography
within the patches is simplified and the studied pa-
rameters are the patch shape, roughness coverage ra-
tio, and heterogeneity length-scale ΛP (defined as the
square root of the total area divided by the number of
patches). We show that, irrespective of the patch ge-
ometry, at roughly ΛP /δ > 10 the skin-friction coeffi-
cient virtually reaches an equilibrium value (δ is chan-
nel half height). Overall, the results suggest that the
friction coefficient of heterogeneous roughness may
be predicted by extending the existing homogeneous
roughness models with a minimal number of added
parameters including ΛP /δ.
References
D. Chung, N. Hutchins, M.P. Schultz, and K.A. Flack. Predicting the Drag of Rough Surfaces. Annu. Rev.
Fluid Mech. 53:439–71, 2021.
J. Yang, A. Stroh, S. Lee, S. Bagheri, B. Frohnapfel, and P. Forooghi. Prediction of equivalent sand-grain size
and identification of drag-relevant scales of roughness – a data-driven approach. J. Fluid Mech. 975, A34,
2023.


The path from homogeneous to heterogeneous roughness drag models

Hunsucker*, K.

Franklin, G.

Tate, M.

Schultz, M.

Hunsucker, T.

 
 
XI International Conference on Computational Methods in Marine Engineering 
 
 
Reducing Biofilms and the Associated Drag Penalties:  
Studies into the Impact of UVC Applications for Dynamically  
Grown Marine Biofilms 
 
Kelli Z. Hunsucker1*, Geligne Franklin1, Madison Tate1, Michael P. Schultz2, J. Travis Hunsucker3 
 
1 Center for Corrosion and Biofouling Control, Florida Institute of Technology,  
Melbourne Florida, USA 
2 Dept. of Naval Architecture & Ocean Engineering, United States Naval Academy,  
Annapolis, Maryland, USA 
3 Hydromechanics and Naval Architecture Lab, Florida Institute of Technology,  
Melbourne Florida, USA 
 
* khunsucker@fit.edu 
 
ABSTRACT 
 
The growth of marine biofilms can lead to functional and financial problems for the shipping industry. 
Application of ultraviolet light (UVC) is of growing interest for biofilm prevention. Most of the current 
research on UVC in the marine environment has focused on growth under static conditions, not taking into 
consideration the different communities and structure of biofilms which form under flow regimes. This 
experiment was designed to examine how biofilm which forms under flow can be reduced by the application 
of UVC and how these changes manifest in improvement of drag penalties for ships.  
 
Field biofilms were allowed to accumulate on epoxy-coated panels (10 cm wide x 75 cm long) in an open grow 
channel (10 cm wide x 300 cm long) for approximately one week. The panels were assessed for percent cover, 
thickness, chlorophyll a content, and microbial composition. Panels were then placed in a separate field 
deployed flow channel (Reτ ~ 2.5 x 103) to measure drag using streamwise pressure gradient. Drag penalties 
were determined from comparisons with the panel in the clean condition. After the initial drag measurements, 
panels were placed back in the grow channel for UVC treatment. A UVC dose (254 nm) was applied, with 
minimal flow in the grow channel to represent a pier-side ship. The biofilm assessment and drag measurements 
were repeated after the UVC treatment.  
 
The experiment was designed to mimic a ship duty cycle- dynamic biofilm growth while underway and then 
a UVC treatment while in port. This process was repeated at different time periods to account for seasonal and 
environmental changes that influence biofilm growth. Results demonstrate that UVC can significantly reduce 
biofilm formation under flow, which results in lower drag penalties. This presentation will also discuss the 
importance of understanding how ecological changes in biofilms can manifest in the frictional drag and how 
matching the correct UVC dose with these changes can improve biofouling management strategies.  
 


Reducing Biofilms and the Associated Drag Penalties:  Studies into the Impact of UVC Applications for Dynamically  Grown Marine Biofilms

Seshasayee*, M.

Attili, A.

Hamblett, P.

Viola, I.

XI International Conference on Computational Methods in Marine Engineering
RANS modelling of heterogeneous roughness
Mridu Sai Charan Arukalava Seshasayee1, Antonio Attili1, Michael P. Schultz2, Paul Hamblett3, and
Ignazio Maria Viola1,∗
1 School of Engineering, University of Edinburgh
The King’s Buildings, Robert Stevenson Road, Sanderson Building Edinburgh, EH9 3FB, UK
2 United States Naval Academy
3 International Paint Ltd
∗ i.m.viola@ed.ac.uk
ABSTRACT
Studying the growth of boundary layers over rough surfaces and the consequent effects on skin friction and
drag is essential for applications in fluid mechanics, such as the flow over ship hulls, aircraft wings, and atmo-
spheric boundary layers. In these applications, Reynolds-Averaged Navier-Stokes (RANS) models are com-
monly employed to predict the wall shear stress and the velocity profile over rough surfaces. However, while
it is established that RANS models can accurately predict the flow over smooth or uniformly rough walls, it is
unknown, whether these models can predict the flow over step changes in roughness height. To this end, RANS
is used to model previously conducted experimental studies of boundary layers over smooth and rough surfaces
and surfaces with a streamwise step change from rough to smooth and smooth to rough. Results demonstrate
good agreement with experimental data for velocity profiles and turbulent kinetic energy, both upstream and
downstream of the transition, as well as in the region near the transition. The simulations also accurately predict
the growth of the internal boundary layer, revealing how the boundary layer adapts to the new wall boundary.
Furthermore, although the availability of experimental data for the skin friction coefficient across the rough-to-
smooth transition is limited, the simulations show consistent results with those observed in other high-fidelity
numerical studies in comparable conditions. Overall, this study reveals that RANS can accurately predict the
mean flow field and kinetic energy over spanwise heterogeneous roughness and thus provides confidence in us-
ing these models for industrial applications. Further work is needed to verify the RANS accuracy in predicting
the wall shear stress in the region near the roughness step change.


RANS modelling of heterogeneous roughness

Carvalho, Gustavo

Hasan, U.

Pereyra, E.

Mesa*, J.

XI Conference on Computational Methods in Marine Engineering (MARINE 2025) 
June 23-17, 2025, Edinburgh, Spain 
 
 
DATA DRIVEN APPROACH TO DEVELOP A MULTIPHASE 
METER FROM THE FLOW INDUCED VIBRATION IN SUBSEA 
JUMPERS 
GUSTAVO CARVALHO, PH.D.1, SYED UMAIR HASAN, PH.D.1, EDUARDO 
PEREYRA, ASSOCIATE PROFESSOR1, JOSE D. MESA, PH.D.
2 
 
1 University of Tulsa, 
800 S Tucker Dr, Tulsa, OK 74104 
2 
Anaconda Inc., 
6335 Prairie Landing Blvd, Katy, TX 77493 
jmesa@anaconda.com 
 
 
ABSTRACT 
 
The measurement of the gas and liquid production from a subsea well is of the 
critical importance for the production optimization. This is usually done by installing 
multiphase meters or virtual flow meters that required calibration with certain 
frequency. 
 
All subsea wells are equipped with jumpers to absorb the deformation of the pipes 
due to temperature and pressure changes. Jumpers are flexible or rigid pipe sections 
that connect various subsea components, such as wells, manifolds, risers, and 
flowlines. The dynamics of the gas and liquid through the jumper generates structural 
vibrations which depend on the liquid and gas flowrates. 
 
Understanding the relationship between flowrates and their subsequent vibrations, it 
will be possible to estimate the well production from the vibration measurements. 
This study evaluates the possibility of creating an inverse model to estimate flow 
rates based on signals generated in an experimental facility. Signals acquired by 
different sensors are used to train a model capable of predicting the flow rate from 
the acquired signals.  
 
This session involves the use of technology and data driven approach to study the 
multiphase production techniques in an environment with high vibration response 
and strong structural integrity requirements. 
 
 


Data-Driven Approach To Develop a Multiphase Meter From The Flow Induced Vibration In Subsea Jumpers

Cook*, T.

Micklem, L.

Dong, H.

Yang, Y.

Mistry, M.

Giorgio-Ser, F.

XI International Conference on Computational Methods in Marine Engineering
Gust Estimation and Rejection for Underwater Crafts with Morphing Control
Surfaces.
Tobias Cook1, Leo Micklem1, Huazhi Dong1, Yunjie Yang1, Michael Mistry2 and Francesco
Giorgio-Serchi1,∗
1 School of Engineering, University of Edinburgh
The King’s Buildings, Alexander Crum Brown Road, Scottish Microelectronics Centre, EH9 3FF,
UK
2 School of Informatics, University of Edinburgh
Potterow, The Bayes Centre, EH8 9BT, UK
∗ f.giorgio-serchi@ed.ac.uk
ABSTRACT
Autonomous underwater vehicles are essential for sur-
veying and maintenance tasks at sea. However, dif-
ferently from deep-sea environments, operations in
shallow waters can be daunting or altogether unfea-
sible due to the occurrence of severe hydrodynamic
disturbances. Disturbances generated by waves, cur-
rents and turbulence vary across a broad spectrum
of temporal and length scales and can dramatically
impact the stability and performance of autonomous
self-propelled vehicles, critically hindering their op-
erational envelope.
In nature, the interaction with highly non-stationary
flows is dealt with by ocean dwelling organisms by
means of continuously deforming fins and tails which
can actively or passively mitigate the impact of the
unsteady flow patterns. Inspiration can be drawn
from such specimens in the design of morphing wings
and their control systems to enable engineered self-
propelled systems to better cope with unwanted dis-
turbances for improved maneuverability and propul-
sive efficiency.
Here we demonstrate a nonlinear controller and dis-
turbance estimator for the purpose of gust rejection of
morphing control surfaces. We make use of a propri-
oceptive underwater morphing wing (Micklem et al,
2022) which employs soft hydraulic actuators to ad-
just its own camber and which relies on a flexible e-
skin for real time shape estimation. We develop and
validate a dynamic model of the soft wing and derive
a non-linear observer that successfully estimates the
sudden change in angle of attack due to a gust and
corrects the wing camber accordingly to minimize un-
wanted deviations in the lift force.
Our results show excellent disturbance rejection performances, offering the chance to endow underwater craft
with superior stability and maneuverability during gliding and station keeping tasks even when subject to ag-
gressive environmental perturbations.
References
L.Micklem, G.D.Weymouth and B.Thornton. Energy-efficient tunable-stiffness soft robots using second mo-
ment of area actuation. In 2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS),
2022


Gust Estimation and Rejection for Underwater Craft with Morphing Control Surfaces

Shin*, K.

Kim, M.

Hong, J.

Ahn, B.

Nielsen, J.

 
 
XI International Conference on Computational Methods in Marine Engineering 
 
 
CFD Prediction of Tip Vortex Cavitation Inception on a Hydrofoil 
 
Keun-Woo Shin1,*, Mina Kim2, Ji-Woo Hong2, Byoung-Kwon Ahn2 and Jens R. Nielsen1 
 
1 Propeller & Aftship R&D Department, MAN Energy Solutions,  
Frederikshavn 9900, Denmark 
 
2 Department of Naval Architecture and Ocean Engineering; Chungnam National University, 
Daejeon 34134, Korea. 
 
* keun.shin@man-es.com 
 
ABSTRACT 
 
It is important to predict and delay the inception of tip vortex cavitation (TVC), that is, often the first cavitation 
type shown at the lowest inception speed on marine hydrofoils, propulsors and appendages because the levels 
of pressure pulses and underwater noise can be increased by more than an order of magnitude after the 
cavitation inception (Shin et al. 2021). 
 
TVC on a symmetric planform hydrofoil with a NACA16-020 cross-section is predicted by CFD simulations. 
The computational domain and condition are prepared by following the setup of the cavitation tunnel test 
conducted in CNU-CT (Nagarathinam et al. 2022). A discretized computational model is refined in process of 
validation against the experimental results of TVC trajectory, sheet cavitation variation and pressure pulses in 
conditions showing fully developed cavitation. CFD is carried out with an Eulerian multiphase flow model 
and a cavitation model based on the asymptotic Rayleigh-Plesset equation. Different CFD solvers such as LES 
and RANS with isotropic and anisotropic turbulence models are adopted for evaluating the suitability of 
numerical methods in terms of computational effort and accuracy as a practical tool in marine appendage 
design. 
 
The criterion for determining cavitation inception is established through an iterative process by adjusting the 
threshold value of cavity volume. The cavity volume within a certain wall distance is excluded due to 
discretization error. Diagrams for the inception cavitation number with respect to the incident angle are 
prepared for comparison with the experimental measurement. The effect of the seed density is investigated as 
a crucial factor calibrating cavitation inception. 
 
The high-fidelity CFD approach has advantage in reproducing dynamic behaviours of unsteady cavitation and 
predicting inception speeds of detached TVC. RANS with an isotropic turbulence model can be a practical 
approach as a computationally efficient method in predicting inception speeds of attached TVC in spite of 
underprediction of detached cavitation. 
 
 
Figure 1. Cavitation on the NACA16-020 planform hydrofoil:  
(a) Cavitation tunnel test (Shin et al. 2021), (b) LES 
 
References 
 
S. Shin, J.W. Hong, D. Nagarathinam, B.K. Ahn and S.G. Park. Tip vortex cavitation and induced noise 
characteristics of hydrofoils. Applied Sciences, 11, 5906, 2021. 
 
D. Nagarathinam, J.W. Hong, B.K Ahn, C. Park, G.D. Kim and I.S. Moon. Dynamics of tip vortex flow over 
three-dimensional hydrofoils by LDV measurements. Ocean Engineering, 266, 112748, 2022. 


CFD Prediction of Tip Vortex Cavitation Inception on a Hydrofoil

Ernesto, V.

Lee*, I.

 
 
XI International Conference on Computational Methods in Marine Engineering 
 
A CFD-based Performance Prediction of Roller Wing Sail for Wind-Assisted 
Ship Propulsion 
 
Vivar Levakova Armando Ernesto1 and Inwon Lee1,* 
 
1 Department of Naval Architecture & Ocean Engineering, Pusan National University 
Geumjeon-gu, Busan 46241, Republic of Korea. 
 
* Corresponding. inwon@pusan.ac.kr 
 
ABSTRACT 
In this study, a parametric study on the characteristics of a plain wingsail was carried out using numerical 
calculations. Later, in order to improve the aerodynamic performance, the plain wing was fitted with a rotary 
cylinder (denoted as “roller”) on the suction side. As the first step for the wingsail analysis, a cylinder is 
installed in a plain airfoil. Then, the cylinder location was systematically changed, aiming to find the optimal 
location of the cylinder. The simulations were performed using the same assumptions and mesh used in the 2D 
analysis of the plain wing. For the rotor to have a positive effect and help move the flow separation point, it is 
important to set the rotor before the flow separation occurs. The simulation results showed that the optimal 
location of the cylinder is located at one meter (x/C = 40%) from the leading edge (Fig. 1). As can be observed 
in Fig. 2 that the simulation results showed that the highest lift coefficient is obtained when the cylinder spin 
ratio is 4, improving the lift coefficient by almost 25% (Fig. 2).  
  
Fig. 1. Comparison of the wing sail lift with the 
stationary cylinder at variable locations 
Fig. 2. Comparison of wing sail lift with the rotating 
cylinder 
 
When employing wind propulsion systems within the framework of the Energy Efficiency Design Index (EEDI) 
regulations, users must utilize the global wind probability matrix to appropriately account for the impact of the 
wind propulsion system. However, recent years have witnessed substantial controversy concerning the 
precision of this wind probability matrix. Hence, it becomes necessary to conduct an investigation into the 
performance of the 3 rigs, plain wingsail, rotor sail, and the present optimized wing sail, excluding the 
utilization of the wind speed and direction probability matrix provided by the IMO. The calculation results are 
presented in the Table 1. This difference represents the 8% for the plain wing and 11% for the Roller wingsail.  
 
Table 1 Comparison of the available effective power for 1 unit 
 Plain wing sail Roller wing sail Rotor sail 
𝐹 ∙ 𝑃  (kW) 561.3 610.0 489.3 
References 
I. M. Viola, M. Sacher, J. Xu, and F. Wang. A numerical method for the design of ships with wind-assisted 
propulsion. Ocean Engineering, 105, 33-42, 2015 


A CFD-based Performance Prediction of Roller Wing Sail for Wind-Assisted Ship Propulsion

Not a member yet