Japan Bulk Carrier Research Articles

Optimising ship principal dimensions with a Dung Beetle Optimizer and random forest proxy model

ABSTRACT Shipping serves as an important component of global trade, with speed being a key attribute closely tied to navigational resistance. Amid rising marine pollution, the International Maritime Organisation (IMO) requires shipowners to modify ships to comply with existing requirements. Herein, focusing on the static water sailing resistance, whole-ship hull line optimisation was conducted for Japan Bulk Carrier (JBC). The optimisation included the bulbous bow, inflow and outflow sections, and the parallel mid-body. Initially, a random forest resistance proxy model was introduced to replace traditional Computational Fluid Dynamics (CFD) methods. The model’s hyperparameters were optimised using the Dung Beetle Optimizer algorithm. Subsequently, this algorithm was employed to optimise ship design parameters. Finally, comparisons confirmed the proxy model’s high precision, and the optimisation yielded substantial outcomes, achieving a 4.7% decrease in resistance.

Propeller–hull interaction simulation for self-propulsion with sinkage and trim

This paper presents numerical simulations of propeller–hull interaction of a ship model for the dynamic condition, demonstrating the ability of the developed self-propulsion module in OpenFOAM. A dynamic motion class has been developed based on the sliding mesh method to simulate a rotating propeller with ship motions. A body-force method is also implemented to simulate propeller–hull interaction to reduce the computational cost of propeller modeling. Validation studies were carried out for the Japan Bulk Carrier (JBC) ship model. The bare-hull resistance, sinkage, and trim are verified against the experimental data. The propeller open-water hydrodynamic characteristics are then computed and validated using sliding mesh and body-force methods. Finally, the self-propulsion simulations are carried out for the JBC model in calm water with sinkage and trim at the design speed. Numerical predictions of the self-propulsion parameters and axial flow velocity distributions at different transverse locations are presented.

Experimental assessment of the hydrodynamic characteristics of a bulk carrier in off-design conditions

This paper presents an extensive experimental study on the resistance and propulsion characteristics of the Japan Bulk Carrier in off-design conditions. The experimental campaign is carried out for a ship model at a scale of 40.264 for three loading conditions. Resistance, open water, and self-propulsion tests were performed at the Brodarski Institute for a wide range of speeds. Four extrapolation methods, based on different assumptions, were applied to predict the resistance and propulsion characteristics of the full-scale ship from model-scale experiments. The differences between the results obtained by different extrapolation methods and the effect of loading conditions on ship resistance and propulsion characteristics are discussed. This study provides a benchmark database for the validation of Computational Fluid Dynamics simulations.

Turning circle tests with system-based simulations in irregular waves including wave drift and propeller side forces

Controlled motion in seas require mathematical modeling of ship motions under external disturbances. Waves are one of the most influential factors that undermine ship control. In this study, we investigate the maneuvering ability of the benchmark Japan Bulk Carrier (JBC) in calm water and in waves. Turning circle tests are conducted via system-based analysis and direct CFD method in calm water condition. Comparison of system-based analysis with experiments and direct CFD method have shown to be satisfactory. After validation of the mathematical model, empirical relations are used to include the ship drift in irregular wave conditions. Two different cases are considered. The first one is with constant significant wave height and changing wave angles. The second case is with constant wave angle but different significant wave height. The ship drift was observed to be in the direction of wave propagation, growing larger with increasing wave height. The maneuvering indices with changing wave directions were graphed and it revealed the maneuvering capability of JBC under the disturbance of waves.

Investigation of the Effects of the Pre-Duct in a Ship on Propeller–Hull Interactions Using the CFD Method

The power requirement of a ship propulsion system is directly proportional to the fuel consumption and the emissions released. By reducing the engine power, the fuel consumption and emissions can be reduced. One of the energy saving devices (ESDs) that is positioned in a region between the stern hull and propeller is the pre-duct. The ESD can improve the propulsive coefficient of the propulsion system. This research explains the effect of a circular pre-duct on the hull-propeller interaction. A numerical simulation uses the Japan bulk carrier (JBC) standard model for the hull and propeller. A circular pre-duct was applied to the ship with different diameters, stands, and lengths of the chord. The simulation has already been validated with the result of the resistance and self-propulsion test in the towing tank. The results show that the diameter of the pre-duct affects the water flow to the propeller. The model with 1Dp can make the positive value of the propulsive coefficient be about 1.72%. The size of the foil chord of the pre-duct can improve the performance until 2.88% at 1D 2S NS model. The stand of the pre-duct has a bad effect on the propulsive coefficient. The enlarged shape of the foil pre-duct can increase the water flow on the suction side. Also, making the diameter larger than the propeller diameter and eliminating the stand on the pre-duct make the incoming flow has no resistance or damages the rotary flow before the propeller. So that, the rampant flow to the propeller becomes larger and there are no significant obstacles until the propulsive coefficient value increases significantly.

Ship specific optimization of pre-duct energy saving devices using reduced order models

Hydrodynamic energy saving devices (ESD) have been widely explored as an effective alternative to improve energy efficiency of vessels by reducing losses across propellers, especially in the presence of strong interactions between hull and propellers. In this work, we propose a computational optimization framework for the design of pre-duct ESD for a specific hull form. For optimization of duct geometries, the framework is based on computational fluid dynamic (CFD) approach for prediction of hull resistance as well as propeller performance under changes in the design of pre-swirl duct geometrical parameters. We have implemented two improvements in the numerical procedure to speed up simulations; enabling the affordable computational design of the duct. First, an overset grid approach is used to realize a change in duct geometries on a background solution of flows over the hull and propeller only. This accelerates the convergence of RANS simulations for a specific design. For every single optimization loop, the propulsive energy efficiency was calculated using proper-orthogonal decomposition (POD) based reduced-order model for the hull, propeller, and duct. Using the POD interpolation technique it is possible to predict the resistance of hull and duct as well as propeller thrust at a particular design parameter using offline flow solutions pre-computed with a sample of design parameters. The accelerated CFD approach has been applied for design of pre-swirl duct on the Japan Bulk Carrier hull using the surrogate-based optimization approach. The performance of the propeller at the optimal design of the duct is simulated with CFD and compared with an earlier proposed duct design. The optimization framework demonstrates the potential of the approach for future applications for the design of ESDs for specific hulls, especially in retrofitting ships.

Multi-fidelity model and reduced-order method for comprehensive hydrodynamic performance optimization and prediction of JBC ship

The multi-fidelity Co-Kriging surrogate model can be applied to combine the accuracy advantage of high-fidelity sample evaluation with the efficiency advantage of low-fidelity sample evaluation. In this paper, the hull form optimization process for resistance and wake performance of a Japan bulk carrier (JBC) hull at design speed is given in detail, where the evaluation results from medium and coarse grids are regarded as the high- and low-fidelity data, respectively. 60 high-fidelity hydrodynamic evaluations have been done to construct the Kriging model, while the Co-Kriging model uses 30 high-fidelity and 60 low-fidelity evaluations with a 25% reduction of the total computation time. The optimization results show that, for the total drag, the Kriging-based optimal hull has a 4.57% reduction, while the Co-Kriging-based optimal hull has 5.67%; for the axial wake fraction reduction at the propeller disk, the Kriging-based optimal hull has a 7.20% reduction, while the Co-Kriging-based optimal hull has 10.37%. Furthermore, in the latter stage of hull form optimization, dimensionality reduction field learning can be performed to fully use the viscous-flow-based calculation results. An accurate and efficient viscous-flow-based wake field learning method is proposed based on the Kriging model and the Proper Orthogonal Decomposition (POD) method with qualitative and quantitative error analysis, which can guide the sensitivity analysis of the design variables, the selection of the design variables and spaces, and new flow field prediction for comprehensive hull form performance optimization.

CFD assessment of the wind forces and moments of superstructures through RANS

In addition to wind tunnel tests and regression formulae, numerical simulation has begun to be used at the design stage of ships as a method for estimating the wind force and moments of superstructures. However, no specific approach has been proposed to verify the grid dependence around superstructures, and the degree to which differences in computational conditions affect the results has not yet been systematically clarified. Therefore, a new approach to grid sensitivity analysis is carried out. The effect of some computational conditions on the computed result is investigated using an in-house solver with an overset grid technique with a Japan Bulk Carrier(JBC) model. The method that verifies the grid sensitivity of the hull and the superstructures separately can obtain equivalent results to the method of simultaneously verifying both of them. The grid sensitivity analysis of the superstructures can be performed separately from the hull. The comprehensive comparative study reveals five findings: the blockage effect of the tank size is slight, the steady-state computation is capable of estimating as well as unsteady computation, wall function can be applied to object surfaces, a difference of wind profiles of incident flow can be recovered by the normalization based on the momentum integration in a shear flow, and the Reynolds number effect does not need to be considered if it is greater then 1.0×106. The computations for other ship types are also performed. The computed results show good agreement with the measured data, while the regression formula shows differences from the measured data in some cases. The above study has shown that steady-state CFD analysis is capable and viable in estimating the wind forces and moments of superstructures of a ship model in a wind tunnel for various ship types.

Design of Energy-Saving Duct for JBC to Reduce Ship Resistance by CFD Method

The present work is to modify the stern duct of Japan bulk carrier (JBC) to reduce the ship total resistance for Froude number 0.142. The research method is to use the CFD (computational fluid dynamics) tool OpenFOAM to predict the total resistance and viscous flow field around the ship hull considering the free surface. First, the V&V (verification and validation) analysis was conducted to ensure our CFD method is reliable, and to estimate its error and uncertainty range for the original JBC with and without the original stern duct. Second, the angle of attack (AoA) of the foil section of the stern duct was adjusted, thus forming a series of different ducts axisymmetric along the propeller shaft axis. The CFD simulations were performed for each duct appended behind the ship hull. By comparing the total resistance with and without the duct, the ship hull resistance reduction effect caused by the duct would be obtained. Finally, the duct with 7° AoA achieved the best resistance reduction of 2.49%. The original duct (with 20° AoA) could only provide a 0.6~0.7% reduction. The nominal wake was also analyzed with the ducts, in order to understand the detailed flow phenomena which had an essential influence on propeller inflow.

Resistance and wake distortion optimization of JBC considering ship-propeller interaction

In this paper, the self-propulsion performance of a full formed hull is optimized by the in-house hull form optimization software OPTShip-SJTU 2.1. In the field of hull form optimization, complex hull optimizations such as hull-propeller interaction optimization have not launched a full investigation. To break through this limitation, the hull-propeller interaction module is brought into the software. We conduct a hull-propeller interaction design optimization of Japan Bulk Carrier (JBC) with an actual propeller (AP) based on CFD considering ship resistance and propeller wake distortion at Fr = 0.142. Hull form deformation module is applied to change the stern shape of the JBC. The in-house CFD software naoe-FOAM-SJTU is applied to calculate the hull resistance and wake fraction. The dynamic overset grid method is used to achieve the interaction between hull and propeller and obtain the high-fidelity flow field during the optimization processing. A multi-objective genetic algorithm (NSGA-II) is applied to obtain the optimized hull forms based on the Kriging surrogate model. The influences of propeller for the flow field around stern are also studied. Results indicate: (I) OPTShip-SJTU 2.1 can optimize the coupled hydrodynamic performance in complex hull form optimization. (II) The hull resistance and wake fraction have a strong positive correlation under the deformation setting in this paper. (III) Contraction of hull line at the stern can suppress the flow separation around the stern which is benefit for reducing the pressure resistance and improving the propeller wake distortion. (IV) It is necessary to consider the interaction between propeller and hull together in hull form optimization. The interactions between the shape of stern, propeller performance, and flow field around stern are discussed preliminary, which provide several references for the subsequent research.

Local flow assessment of the Japan Bulk Carrier using different turbulence models

Ship resistance and powering represent the most important aspects in the initial design stage of the ship. Based on their estimation the basic milestone for selecting the main engine and the propulsion system is established. The majority of ships in the international fleet nowadays rely on the screw propeller working in the wake zone behind the ship. The wake flow of the ship has a direct impact on the propeller performance and the propulsion efficiency. Accurate prediction of the nominal and effective wake is crucially important to provide a proper understanding of the flow where the propeller will perform. From this point of view, the wake flow of the Capesize Japan Bulk Carrier (JBC) is assessed using a viscous flow Computational Fluid Dynamics (CFD) method. Numerical simulations are performed to predict the nominal and effective wake of the ship by making use of the viscous flow solver ISIS_CFD of the FINETM/Marine software provided by NUMECA. The solver is based on the finite volume method to build the spatial discretization of the transport equation to resolve the Reynolds-Averaged Navier-Stokes (RANS) equations. Closure to turbulence is achieved using different turbulence models in order to investigate their accuracy in predicting the complex wake flow of the ship. Two-phase flow approach is used to model the air-water interface where the Volume of Fluid method is implemented to capture the free-surface. The results for both nominal and effective wake are assessed against the experimental data provided by the National Maritime Research Institute (NMRI) and Yokohama National University in Japan that were presented in the seventh Workshop on CFD in ship hydrodynamics (Tokyo2015). The results validation showed a reasonable agreement compared to the experimental data for both nominal and effective wake. As it was expected, some turbulence models showed to be more accurate in predicting ship wake, especially the Shear Stress Transport (K-ω SST) and Explicit Algebraic Reynolds Stress (EASM) Models. A special investigation of the flow vortices is also taken into consideration.

Surrogate model based uncertainty quantification of CFD simulations of the viscous flow around a ship advancing in shallow water

Usually, Computational Fluid Dynamics (CFD) simulations are carried out under deterministic conditions. However, there are actually many uncertain factors such as fluid properties, boundary conditions and working parameters that may have effects on the system response. It is critical to study the uncertainty propagation in the stochastic CFD model. In this paper, one of surrogate models for uncertainty quantification (UQ) problems, non-intrusive polynomial chaos (NIPC), is introduced. Stochastic two-dimensional cavity flow with uncertain lid velocity is taken as a study case to verify the effectiveness of NIPC method in comparison with Monte Carlo (MC) method. The results show that NIPC method can greatly improve the efficiency of UQ; the influence of velocity uncertainty has obvious directivity in the flow field and the fluid viscosity has retardation effect on uncertainty propagation. Then the NIPC method is applied to quantify the uncertainty of resistance, sinkage and trim of the Japan Bulk Carrier (JBC) model advancing with an uncertain speed in shallow water. Numerical simulations are carried out using the RANS-based CFD method. The UQ results indicate that the uncertainty of relevant variables can be evaluated accurately with small samples, and under the same sampling points, the higher the order of polynomial chaos expansion (PCE), the more accurate the UQ results.

CFD study of hull wakes in oblique flow at model and full scales

The characteristic of hull wake for a ship operating in oblique flow significantly affects the ship performance at off-design conditions. This paper presents a numerical study on the hull wakes under oblique flow conditions and analyzes the scale effect. RANS method combined with SST k-ω turbulence model is adopted and an international benchmark ship, Japan Bulk Carrier (JBC), is computed. Drift angles ranging from 0° to 20° with an interval of 5° are considered. Results show that the oblique flow considerably changes the hull wake field. Unlike a left-right symmetric pattern at zero drift angle, the nominal wake in oblique flow conditions shows a strong asymmetry since the flow at the windward side is close to the incoming flow whereas the flow at the leeward side is featured by the vortices detached from the hull. It is also revealed that the mean wake fraction decreases as the drift angle increases. Both model and full scales are simulated and the comparison between them shows significant differences in the wake pattern on the leeward side and the magnitude of the mean wake fraction. Compared with the model scale, the full scale has a stronger aft-body vortex and a smaller mean wake fraction.

Parametric study of added resistance and ship motion in head waves through RANS : Calculation guideline

A comprehensive parametric study concerning added resistance and ship motion in head waves is conducted with an overset approach based on a structured grid system using an in-house Navier-Stokes solver and recommended configurations are proposed as a guideline. The overset approach enables studying wave propagation separately from viscous flow around a hull by omitting the grid for the hull. The parametric study on computing wave propagation of different configurations without a hull in different wavelengths provides recommended domain size, grid resolution and computational conditions such as the time interval. Computations with a hull of Japan bulk carrier (JBC) are conducted to investigate interactions between incident waves and ship motions by using the overset approach. Surge motion can be fixed, and wall function can be applied to the near-wall region. The obtained configuration is applied to a different hull form, the Duisburg Test Case (DTC) and computed results show good agreement with measured data. The achieved configurations are validated and provide a common practice for computing the added resistance and ship motion in head waves by using the flow solver with the described numerical framework.

A Mesh Deformation Method for CFD-Based Hull form Optimization

Computational fluid dynamics (CFD) is an effective tool for ship resistance prediction and hull form optimization. A three-dimensional volume mesh is essential for CFD simulation, and mesh generation requires much time and effort. Mesh deformation can reduce the time for mesh generation and simulation. The radial basis function (RBF) and inverse distance weighted (IDW) methods are well-known mesh deformation methods. In this study, the two methods are compared and a novel mesh deformation method for hull form optimization is proposed. For the comparison, a circular cylinder polyhedral mesh was deformed to the National Advisory Committee for Aeronautics (NACA) 0012 mesh. The results showed that the RBF method is faster than the IDW method, but the deformed mesh quality using the IDW method is better than that using the RBF method. Thus, the RBF method was modified to improve the deformed mesh quality. The centroids of the boundary layer cells were added to the control points, and the displacements of the centroids were calculated using the IDW method. The cells far from the ship were aligned to the free surface to minimize the numerical diffusion of the volume of fluid function. Therefore, the deformable region was limited by the deformed boundary, which reduced the time required for mesh deformation. To validate its applicability, the proposed method was applied for varying the bow shape of Japan Bulk Carrier (JBC). The resistances were calculated with the deformed meshes. The calculation time was reduced to approximately one-third using the result of the initial hull form as the initial condition. Thus, the proposed mesh deformation method is efficient and effective enough for CFD-based hull form optimization.

Design of Wake Equalizing Ducts using RANSE-based SBDO

We propose a Simulation-Based Design Optimization (SBDO) approach for the design of an Energy Saving Device (ESD) based on the Wake Equalizing Duct (WED) concept. Pre-Ducts, like Wake Equalizing Ducts, reduce the wake losses, improve the propeller-hull interaction and generate an additional thrust. An integrated design approach, relying on a parametric description of the duct geometry of the WEDs and on a RANSE method, managed by a global convergence optimization algorithm, is developed to maximize the delivered thrust. The Japan Bulk Carrier (JBC) test case, for which model scale experimental data on the effectiveness of the WED are available in the literature, is considered as a baseline. Results obtained by using the adaptive, fully automated proposed design framework highlight significant improvements of the overall propulsive efficiency when the Pre-Duct design is tailored to the actual hull wake shape. In addition, off-design conditions are considered to verify the robustness of the proposed designs with respect to variations of the working point and discuss the opportunity of a robust optimization process.

The Improvement of the Powering Performance on the Japan Bulk Carrier (JBC) using Rudder Thrust Fin as a Post-Swirl Stator

Post Swirl Stator (PSS), also known as the 'Energy Saving Device (ESD) Behind the Propeller' operates within the slip stream of the propeller. The aim of this project is to investigate the powering performance of a JAPAN Bulk Carrier (JBC) upon the installation of PSS. The prediction of resistance and propulsive factors were conducted using CFD simulation using SHIPFLOW CFD code. In order to find the optimised design of the ESD, three parameters were laid out and studied. The parameters are the left side fin length, right side fin length and the orientation of the fins.The aim of this study are to improvise the thrust fin design by changing the parameters to get the optimum powering performance result, and to quantify the powering performance of the JBC upon the installation of PSS in model and full scale. There were 27 different post-swirl stator configurations. All the 27 different configurations were compared in terms of its performance in model and full scale. All the 27 different configurations were simulated using full RANSE. The free surface of the water were modelled using panel method. A grid dependence study was conducted to determine the best grid cell resolution and it was chosen at a total of 7 millions cells. The bare hull resistance of the JBC were validated with available published experiment results. All the thrust fins were modelled using appendage setting in SHIPFLOW. The best thrust fins design were selected in judging its minimum drag, minimum thrust deduction fraction, minimum wake fraction, and the delivered power. It was found that he thrust fins design for case study #20 by CFD is the most optimised configuration in terms of its performance criteria as mentioned earlier. The thrust fins design was able to reduce delivered power to 6.012%. Thrust deduction was also reduced to 2.927%. Total efficiency was increased to 6.709%

Design optimization for self-propulsion of a bulk carrier hull using a discrete adjoint method

Computational fluid dynamics (CFD) based optimization is becoming increasingly popular in hydrodynamic design of ship hulls because it provides a fully automatic framework with a shorter design cycle than a human-supervised design tool. Despite the above advantage, CFD-based optimization requires careful attention to relevant design considerations, such that the final design is useful in practice. These considerations include all relevant objectives (such as drag and wake distortion) and constraints (such as volume, thickness, and curvature). Although constraints have been included in previous hull shape optimization studies, these studies have typically considered only one objective. To address this shortcoming, we conduct design optimization for self-propulsion by simultaneously considering drag and propeller-wake distortion. We use a gradient-based optimization framework that includes a discrete adjoint method for efficient derivative computation, which allows us to use a large number of design variables to parameterize the complex hull shape and thus gain a large amount of freedom for geometric modification. We impose appropriate geometric constraints (volume, thickness, and curvature) on the hull surface to ensure a practical design. In addition, we use a weighted objective function that includes drag and wake distortion to construct a Pareto front with five optimizations. We also consider hull-propeller interaction by comparing optimization results with and without a propeller. We use the Japan bulk carrier (JBC) as the baseline model and focus on optimizing the stern region. We find that optimizing for only one objective results in a large penalty on the other objective, whereas a weighted objective balances the penalty and achieves simultaneous improvement in drag and wake distortion. Moreover, we observe that the suction effect of the propeller suppresses the flow separation near the bilge tube and smooths out the velocity distortion at the propeller plane; these are effects that would end up affecting the optimized shapes. Our results demonstrate that it is necessary to simultaneously consider drag and wake distortion in hull-shape-optimization studies, and that constrained shape optimization with a large number of design variables is possible with the discrete-adjoint method.

Application of a RaNS and PF-Based Method to Study the Resistance and Motion of a Bulk Carrier

Resistance prediction of ships using computational fluid dynamics has gained popularity over the years because of its high accuracy and low cost. This paper conducts numerical estimations of the ship resistance and motion of a Japan bulk carrier model using SHIP_Motion, a Reynolds-averaged Navier–Stokes (RaNS)-based solver, and HydroSTAR, a commercial potential flow (PF)-based solver. The RaNS solver uses an overset-structured mesh and discretizes the flow field using the finite volume method, while the PF-based solver applies the three-dimensional panel method. In the calm water test, the total drag coefficient, sinkage, and trim were predicted using the RaNS solver following mesh dependency analysis, and the results were compared with the available experimental data. Next, calm water resistance was investigated for a range of Froude numbers. The added resistance in short-wave cases was simulated using both RaNS and PF solvers, and the results were compared. The PF solver showed better agreement with the RaNS solver for predicting motion responses than for predicting added resistance. While the added resistance results could not be directly validated because of the absence of experimental data, considering the previous accuracy of the RaNS solver in added resistance prediction and general added resistance profile of similar hull forms (bulk carriers), the prediction results could be concluded to be reliable.

Using a PANS Simulation Approach for the Transient Flow Around the Japan Bulk Carrier

In this study, a partially averaged Navier-Stokes (PANS) modeling approach developed based on the k-ω turbulence model has been applied to the flow around the Japan Bulk Carrier. Three different meshes have been used for a fixed physical resolution for the PANS modeling. The results are encouraging, with small-scale flow dynamics being allowed to develop on reasonably small mesh sizes, but more studies are required before reliable predictive simulations can be performed. 1. Introduction Steady resistance and wake simulations in ship hydrodynamics are currently being performed with relatively high reliability using the Reynolds averaged Navier-Stokes (RANS) simulation approach. There are, however, a number of cases where RANS is not sufficient and a scale-resolving transient simulation approach is needed. This is well established in cases of flow around bluff bodies, e.g., vortex-induced vibrations and flow across cylinders (Pereira 2018), or for ship to ship interaction (Arslan et al. 2015), where the main interest is on global parameters, such as shedding frequency or force variation, but the transient separating flow is not well predicted by RANS simulation. It could also be that details of the transient flow behavior is part of the study, e.g. relating to propeller dynamics (Jang & Mahesh 2013; Bensow 2015; Guilmineau et al. 2017), vortex dynamics (Fureby et al. 2016; Visonneau et al. 2018), or in cavitation (Bensow 2011); in these cases, RANS modeling is inherently not able to capture the details of the governing flow physics because of the underlying averaging. However, it may also be the case where the flow is smoothly separating, or close to, as is the case for the Japan Bulk Carrier (JBC), see Visonneau et al. (2016) and further the discussion below. Using a wall-resolved large eddy simulation (LES) approach is computationally very expensive, with an unfavorable scaling toward full-scale Re numbers (Liefvendahl & Fureby 2017), thus the attention has rather turned toward hybrid RANS/LES approaches or wall-modeled LES; this was used in many of the studies referenced previously, e.g., Guilmineau et al. (2017); Pereira (2018); Visonneau et al. (2018). Grid size estimates for different modeling approaches for simulating the JBC in model scale are given by Liefvendahl and Johansson (2018), amounting to around 2•109 for the wall-resolved LES, 150•106 for the wall-modeled LES, 50•106 for the hybrid RANS/LES, and finally 30•106 for the RANS approach, where the distance between wall-resolved LES and the others will greatly increase with the Re number. In terms of computational effort, one needs to remember that the transient flow approaches, compared with RANS, further needs to include long time-series for sampling statistics.