Flow Behavior Research Articles

Numerical Methods in Modelling of Red Blood Cellflow Behaviour Through a Specific Stacking Pattern

Abstract: The dynamics of red blood cells (RBCs) is one of the major aspects of the cardiovascular system that has been studied intensively in the past few decades. Using computational fluid dynamics, complex nonlinear fluid flows have been modeled. The dynamics of biconcave RBCs are thought to have major influences in cardiovascular diseases and other problems associated with cardiovascular flow behaviour, and the determination of blood rheology and properties. Most reported computational models have been confined to the behaviour of a single RBC in 2-dimensional domains, under physiological flow conditions. This work investigates a particular stacking pattern in analyzing the RBC flow behavior under physiological flow conditions, using the D2Q9 lattice Boltzmann numerical method created using Matlab. Prior to the analysis the Matlab script was benchmarked using the Poiseuille flow and the flow around the cross-section of a cylinder, after which the accuracy of the method used was determined. The benchmarks showed that the lattice Boltzmann code had minimal error. The accuracy was determined using the data obtained from Matlab and a created excel program. It also showed that the lattice Boltzmann method was of the first order, which corresponds with results existing in literatures. The analysis of the stacking pattern showed how RBC flows through the chosen stacking pattern, and the results are shown.

Flow and heat transfer characteristics of low water content jet fuel in U-bend tubes: A numerical study using LES and DPM approaches

This study provides an in-depth analysis of the flow and heat transfer behavior of low-water-content jet fuel (α ≤ 2 %) in U-bend tubes, utilizing Large Eddy Simulations (LES) and Discrete Phase Models (DPM). The research focus on the influence of radii of curvature ratio (r/D), flow rates (Qtp) and α on flow dynamics and heat transfer mechanisms. Flow fields for r/D = 1 and r/D ≥ 2.5, where distinct secondary flow structures, play a critical role in shaping internal flow behavior. These vortices significantly enhance flow mixing and heat transfer, especially on the inner wall, through complex multi-level vortex interactions. The local wall Nusselt number shows a close correlation with vorticity trends, initially increasing and then decreasing, with notable deviations near the inlet and outlet regions. This non-uniform heat transfer is primarily driven by the interaction of secondary flow structures and adverse pressure gradients near the inner wall, while higher Qtp and smaller r/D can improve heat transfer uniformity under certain flow conditions. The presence of droplets increases the total wall Nusselt number by 4 % to 60 % compared to single-phase jet fuel flow, due to two-phase interaction and boundary layer disruption. Finally, the study proposes modified correlations for pressure drop gradients and total wall Nusselt numbers, accounting for effects of r/D and multiphase heat transfer processes. These correlations, validated with RRMSEs of 3.54 % and 6.80 % respectively, provide valuable insights for improving heat transfer efficiency in fuel systems and form a theoretical foundation for real-time monitoring technologies in aircraft fuel lines.

A Comprehensive Methodology for Investigating Cocurrent Spontaneous Imbibition in Coal.

Visualizing and quantifying fluid distribution during spontaneous imbibition at the nanomicro scale is vital for understanding microfluid flow and dynamic wettability in coalbed methane (CBM) reservoirs, which could serve as a fundamental basis for optimizing the parameters of the hydraulic fracturing process. In this study, fluid distribution and flow behavior can be acquired by combining nuclear magnetic resonance (NMR) and in situ X-ray microcomputed tomography (μ-CT) technologies. Meanwhile, spontaneous imbibition stages were studied to analyze gas-water exchange efficiency. Additionally, dynamic wettability of gas-water was calculated during the process of spontaneous imbibition based on NMR. The results show that imbibition characteristics can be divided into three categories based on NMR. In type I, changes in imbibition fluid within nanopores are not obvious, while significant changes occur in micro pore-fractures, especially during the early stage of imbibition (0-2 h) for type I, which is almost the opposite of type II. Coal samples of type III exhibit low porosity and permeability, making it difficult for water to flow through the pores in coal due to capillary forces. The dynamic process of spontaneous imbibition can be divided into four stages using μ-CT equipment, with the third stage displaying the highest imbibition efficiency. This stage is characterized by frequent imbibition fluid exchange among various-scale fractures, which is related to the wettability and pore-fracture of the coal sample. A negative correlation between contact angle and T 2g was observed, where hydrophobic samples corresponded to a smaller geometric average of T 2g in the sample. In addition, the wettability of coal samples changed dynamically during the process of imbibition, with the contact angle gradually decreasing as imbibition time increased, which may be related to the formation of water film and hydration reactions.

Leak-Rate Through Carbon Brush Seals: Experimental Tests Versus Predictions From a Porous Medium Approach

Abstract This study presents a detailed comparative analysis between experimental leakage flow rates and numerical predictions for carbon brush seals with long bristles, utilizing a porous medium model approach. A series of tests were carried out on a static rig (without rotor rotation). The experimental setup allows tests under various interference conditions, revealing significant insights into the flow behavior through the brush seal. A numerical model based on the Darcy-Forchheimer equation is developed to interpret the complex flow dynamics within the brush seal, accounting for viscous, compressible and inertial effects. The study evaluates the impact of brush deformation and porosity on flow resistance, leveraging experimental data to refine the numerical model parameters. This investigation not only deepens the understanding of brush seal flow physics but also improves the predictive accuracy of the numerical model in simulating operational conditions.

Hemodynamic characteristics of pulsatile blood flow through bifurcated stenosed carotid artery

Purpose Carotid artery is often associated with plaque deposition because of its shape and associated flow features. The shape of stenosed bifurcation is characterised by bifurcation angle (ß), planarity angle (α) and severity of stenosis (b). In the present work, three-dimensional numerical computations have been performed to analyse the effect of these geometrical parameters of carotid bifurcation on the characteristics of flow. Design/methodology/approach Governing equations of this study were solved using ANSYS Fluent 20.1 and the blood flow was considered as laminar, pulsatile and non-Newtonian. Instantaneous flow behaviour has been illustrated using vorticity, velocity and helicity contours, whereas the time-averaged wall shear stress ( τw¯) and oscillatory shear index (OSI) quantify the time-averaged behaviour. Findings The recirculation zone and secondary flow are ascertained to be stronger for higher bifurcation angle as compared to the lower bifurcation angle. Strength of the secondary flow is found to reduce with increase in α from 0° to 10°, whereas it grows as α varies from 10° to 20°. For higher bifurcation angles, τw¯ is lower than 2 Pa and OSI is greater than 0.2 on the outer walls. Similar observations were made for τw¯ and OSI distribution on bottom wall in non-planar cases, which predicted atherogenic locations. Originality/value The values for ß were taken as 30°, 45°, 60° and 75°, whereas for α, range of 0°–20° was chosen. The stenosis was considered on the outer wall of internal carotid artery and its severity was considered within the range of 0%–60%.

Machine Learning-Based Predictions of Flow and Heat Transfer Characteristics in a Lid-Driven Cavity with a Rotating Cylinder

Machine learning-based predictions of heat transfer characteristics in lid-driven cavities are transforming the field of computational fluid dynamics (CFD). Lid-driven cavities are a fundamental problem in fluid mechanics, characterized by the motion of a fluid inside a square cavity driven by the motion of one of its walls. The goal of this study was to develop multiple machine-learning regression models and highlight the discrepancies between the predicted and actual average Nusselt numbers. Additionally, the study utilized physics-informed neural networks (PINNs) to model the flow and thermal behavior at both low and high Reynolds numbers. The results were compared among actual data from computational fluid dynamics (CFD) simulations, PINN models trained with CFD data, and purely PINN models created without any prior data input. The findings of this study showed that the random forest model exhibited an exceptional stability in its predictions, consistently maintaining low errors even as the Reynolds number increased compared with other machine-learning regression models. Further, the results of this study in terms of flow and thermal behavior within the cavity were found to depend significantly on the PINN method. The data-driven PINN exhibited a much lower mean average errors at both Reynolds numbers, while the physics-based PINN showed lower physics loss.

Couette flow of micropolar fluid in a channel filled with anisotropic porous medium

This paper presents a mathematical model for the flow of micropolar fluid in a horizontal channel filled with an anisotropic porous medium, bounded by two parallel plates—where the upper plate is stationary, and the lower plate moves at a constant velocity. The flow, driven by both a constant pressure gradient and the movement of the lower plate, is governed by the Darcy-Brinkman equation. Using no-slip and no-spin boundary conditions, we analytically derive expressions for the velocity, microrotational velocity, and stress distributions. The study provides a graphical analysis of the flow behavior influenced by key parameters such as the Darcy number, porous medium anisotropy, anisotropy angle, and the micropolar fluid’s material parameters. Furthermore, the effects of the material parameters and Darcy number on shear stress and couple stress are thoroughly investigated. The findings have applications in modeling fluid flow in striated or fractured rock formations.

Hydrodynamic analysis of core annular flow with a viscoplastic lubricant

Core annular flow (CAF) with viscoplastic lubrication (VPL) is an attractive proposition for pipeline transportation of high viscous oil, slurries and suspensions. Past studies have performed stability analysis to show that the unyielded zone at the liquid-liquid interface stabilizes CAF by suppressing interfacial instabilities. However, an in-depth investigation of the flow hydrodynamics and the conditions which reduce the pumping power within stable CAF range using VPL has not been reported till date. Moreover, most of the studies have considered a Bingham Plastic liquid in the annulus. Only a single study (Usha & Sahu, 2019) is reported with Herschel-Bulkley (HB) liquid in the annulus that considers the entire annulus to be in the shear zone. Another experimental study (Huen et al., 2007) has demonstrated stable core annular flow with a shear thinning core and a HB annulus. In the present work, we analyze viscoplastically lubricated CAF for a Newtonian core where the yield stress annular liquid is described by the generalized HB model. The simplified analysis can predict CAF stability and is further explored to (i) assess the efficacy of VPL for stable energy-efficient oil transportation, and (ii) enhanced throughput without clogging during suspension transportation. The analysis, validated against data from literature, unravels the influence of rheological properties on flow hydrodynamics. We note that an annular liquid with low flow behavior index, n and yield stress, τy lowers pumping power, but the yield stress should be sufficient to form a plug zone at the interface for suppressing instabilities and stabilizing CAF. For viscous oil, a phase diagram in dimensionless coordinates (Reynolds number of the oil core and Herschel-Bulkley number of the annular liquid, both expressed at the inlet conditions) suggests the range of operation where an available HB liquid can serve as an effective annular lubricant for energy-efficient transportation.

A peridynamics approach modeling gas flow in porous media with damaged regions

The study of gas flow within porous media, particularly those characterized by complex pore-fracture networks, is critical for applications in fields such as shale gas engineering, gas extraction, and hydrogeology. This paper proposes a convenient and novel peridynamics approach to describe gas flow behavior in fracture regions and transition regions between fractured and intact regions in porous media, where the bonds naturally describe the interactions between material points in damaged areas. For implementation, we interpolate the permeability of the bonds in the transition region by using local damage values, and adopt a meshfree discretization approach that does not require additional mesh refinement for damaged or fractured regions. Numerical examples are provided and compared with the traditional finite element method to verify the accuracy and effectiveness of the proposed method.

Dot-array porous medium model for windscreen and its simulation accuracy analysis

Porous medium models have long been prevalent numerical computation tools. Although they exhibit swift computational speed, their accuracy in simulating windscreen perforation structures is challenged. This paper introduces the innovative dot-array porous medium (DAPM) model, which accurately portrays the perforation structure and material characteristics of a windscreen by establishing virtual holes on the porous medium. Not only does it simplify modeling by eliminating complex perforation processes, but it also adeptly simulates the flow behavior of the windscreen. The comprehensive comparison between the DAPM model and the physical mesh model, traditional porous medium model, as well as wind tunnel test results, demonstrates that the DAPM model not only possesses rapid computational speed but also delivers outstanding precision in results. In terms of velocity distribution, vortex distribution, and flow intensity in the flow field, the model indicates a high level of accuracy, clearly exceeding that of the porous medium model. Moreover, the DAPM model showcases high versatility and adjustability in practical applications. By adjusting dimension parameters, it demonstrates the capability to precisely simulate any windscreen with holes arranged in a matrix pattern. This research provides an efficient and reliable tool for the numerical simulation of windscreens, with broad application prospects.

Deformation behavior of Gd alloyed CoCrFeNi high entropy alloy at high temperature under the influence of local nano-ordered structure and misorientation

The thermomechanical processing (TMP), which is an industrial process that includes deformation and heat treatment, represents a novel approach to enhancing the mechanical properties of metallic materials. However, it requires extensive research on the high-temperature deformation behavior of alloys during its application process. The present study conducts hot compression tests at 700 °C and 800 °C, as well as detailed microstructural characterization of the deformed material after hot deformation, to comprehensively discuss the mechanical properties and deformation behavior at high temperature of the (CoCrFeNi)100-xGdx (x = 0, 0.5, 1, 2, 3 at.%) HEAs. The (CoCrFeNi)100-xGdx HEAs exhibit an excellent combination of strength and plasticity in high temperature. The original dendritic microstructure in the (CoCrFeNi)100-xGdx HEAs was completely fractured and transformed into a mass of deformed structures during thermal deformation. The mechanical properties at high temperature of the alloy system originate from the misorientation in the microstructure. Dislocation slip is the main deformation mechanism of the alloy system at high temperature. The coordinated deformation of the soft orientation for FCC phase and the hard orientation for HS phase affects the dislocation morphology in the microstructure. Dynamic recovery (DRV) plays a dominant role in the flow behavior of the alloy at high temperature, and work hardening is the main strengthening mechanism during plastic deformation. The correlation between microstructure evolution and mechanical properties of Gd alloyed CoCrFeNi HEAs during hot deformation has been established through comprehensive studies on deformation behavior.

The pinning characteristics of droplets and the self-repair mechanism of lubricating film on nanoporous surface: A molecular dynamics perspective

The nanoscale pore gives rich dynamic information to the flow behavior of the droplets exuded on the SLIPS (Smooth Liquid-Infused Porous Surface). The key to realizing fast self-healing of lubricating film is to understand the dynamic law of droplets at nano-orifice. In this paper, a dynamics model of the exudation and spreading behavior is established by the non-equilibrium molecular dynamics simulation. The characteristics and the mechanism of pinning and spreading of nano-droplets were studied. We found that adjusting the wettability and pore diameter can change the liquid exudation and the pinning time of droplets at the orifice. The weaker wettability and larger pore diameter both can increase the exudation velocity and reduce the pinning time of the droplets, which then improves the spreading of exuded droplets and the self-repairing efficiency of the damaged liquid film. As the pore diameter increases, the spreading area of the droplets on the surface of the pore increases. The increase in the wettability also facilitates the spreading behavior, but the outflow rate of the liquid from the pore decreases. Under the combined effect of the two factors, the spreading area of droplets first increases and then decreases with the wettability increases. The results provide potential insights into the spreading mechanism of nanodroplets on porous surfaces.

Study on the preparation of magnetic Janus nanofluids and oil displacement mechanism

Magnetic nanomaterials, known for their eco-friendliness, low toxicity, strong magnetic response, and reusability, have seen significant advancements in enhancing oil recovery. In this study, the surfactant and magnetic Janus nanoparticles (MJNP) were evaluated and optimized through Fourier transform infrared spectroscopy, ζ potential test, scanning electron microscope, emulsion performance evaluation and other analysis, so as to develop magnetic Janus nanofluids (MJNF). Study the flow behavior and enhanced oil recovery mechanism of this nanofluid in porous media through nuclear magnetic resonance (NMR) and numerical simulation methods. The results showed that when the concentration of surfactant (LAD-30) was 0.08%, the maximum water content of emulsion was 80%, and the viscosity increased by more than 90000%. In addition, when the MJNP concentration is 400 ppm or higher, a stable emulsion is formed at 90 °C. NMR experiment shows that through MJNF oil displacement, the oil recovery of small and medium-sized pores is significantly improved by 25.9% and 18.3%, which indicates that high viscosity emulsion can be formed in situ after MJNF injection, thus achieving consistency control. In addition, the numerical simulation results also found that MJNF injection can improve the oil-water saturation in the pore volume and enhance oil phase flow. The research results provide a new understanding for EOR of emulsion flooding.

Impact of fiber diameter and surface substituents on the mechanical and flow properties of sonicated cellulose dispersions

This study investigates how sonication amplitude and time affect 2 wt% cationic nanofibrils (CCNF) and microfibrils (CCMF) dispersions, focusing on mechanical properties and flow behavior. Sonication reduces fiber diameter and increases the concentration of substituent groups available for hydrogen bonding. This effect becomes significant when diameters fall below 100 nm, leading to enhanced storage and loss moduli. CCNF achieves a maximum shear modulus of 600 Pa, whereas CCMF fibers do not undergo similar size reductions. CCNF's viscosity and critical stress follow a square root relationship with sonication amplitude, due to minimal fiber size reduction at high sonication levels (smaller than 20 nm), unlike CCMF (diameter reduction up to 50 nm), which exhibits a linear increase due to more pronounced fiber fragmentation. At high sonication levels, CCNF shows an exponential rise in critical stress (up to 800 Pa), suggesting tiny fibers infiltrate the hydrogel network, thereby improving its integrity and resistance to shear stresses. By integrating theoretical models with experimental findings, this work presents a unified view of sonication's essential role in fine-tuning the mechanical and flow properties of cellulose-based materials. This research enhances understanding of cellulose dispersion behavior under sonication and provides a foundation for designing optimized cellulose-based materials.

Interaction of microstructure evolution mechanism in Ti-0.3Mo-0.8Ni alloy with initial lamellar microstructure during isothermal compression below the β-transus

The flow behavior and interaction of microstructure evolution mechanisms for a near α Ti-0.3Mo-0.8Ni alloy with as-cast lamellar microstructure are investigated at temperatures of 800∼880 °C in the α+β region with wide strain rate range from 0.01s−1 to 30s−1 during isothermal compression. It is demonstrated that the main reasons of flow softening in the true stress-true strain curves are the kinking of lamellar α, dynamic α→β transformation (DT), dynamic spheroidization (DS), and dynamic recovery (DRV) of β grain. The instability phenomena such as adiabatic shear band (ASB) and flow localization (FL) are the main causes of the stress collapse in the curves at higher strain rate. The dislocation density at the kinking position of initial lamellar α is higher. With the increase of strain rate, the mechanism of the DS changes from flat separation to slat shear. The diffusion of the β-stabilizer results in starting the DT, promoted by the thermodynamic coupling. The interactions between different microstructure evolution mechanisms are extremely complex. In the early stage of hot deformation, the DT promotes the kinking of lamellar α. With the increase of deformation amount, the DT inhibits the DS at higher strain rates, and conversely, the DS promotes the DT. At lower strain rates, the DT and DS accelerate each other in the middle and late stages of hot deformation. The DT and DS are restricted by the process of lamellar α kinking in the middle and late stages of hot deformation.

A comparative study of finite difference approach and bvp4c techniques for water base hybrid nanofluid containing multiple walls carbon nanotubes and magnetic oxide

This study investigates the thermal behaviour of unsteady hybrid nanofluid flow on an infinite vertical plate. The investigation takes into account parameters such as magnetohydrodynamics and radiation effects, as well as the stratified medium. The systems of equations were solved by employing the explicit finite difference approach of Dufort-Frankel method. The main motivation of the study is to compare the performance of water, magnetic oxide, and multi-wall carbon nanotubes as working fluids. Additionally, velocity, temperature, and concentration outlines are visualized through plots, elucidating the fluid behaviour. Tables are provided for the Skin friction, Nusselt number, and Sherwood number, offering comprehensive insights crucial for optimizing performance in engineering applications ranging from thermal management systems to renewable energy technologies. The main finding of this study indicates that the quantitative result reveals that the temperature outline escalates among increasing values of radiation. In contrast, the outlines of a velocity and concentration show a decrease as the values of magnetohydrodynamics increase. In addition, multi-walled carbon nanotubes consume a larger outcome on temperature. A statistical study displays that the thermal stream rate of magnetic oxide-multi-wall carbon nanotubes-water increases from 1.7615 percentages to 7.4415 percentages, respectively, when the volume fraction of nanoparticles rises from 0.01 to 0.05. Future research is important to understanding hybrid nanofluid flows and their applications in thermal engineering systems such as energy systems, nuclear reactors, biomedical applications, electronics cooling, solar thermal systems, chemical processing, and other heat transfer applications where improved thermal performance is crucial.

Impact of surface tension, viscosity, pump settings, and nozzle size on filling process capability and accuracy in high-concentration biopharmaceuticals

Filling is the final critical unit operation in the manufacturing process of liquid biological drug products. This paper thoroughly investigates the influence and mechanisms of peristaltic pump settings, nozzle size, product surface tension and viscosity on the biopharmaceutical filling processes based on the established filling process model of surrogates. Our study highlights the significant role of pump settings in influencing filling process capability indexes, in addition to their primary function of regulating flow rate. Surface tension minimally impacts flow behavior but significantly regulates the final dropʼs behavior, with lower surface tension increasing dripping tendencies. Viscosity proves crucial; higher viscosity intensifies friction and head loss of filling flow in tube/nozzle, causing pressure and flow rate losses, more pronounced dripping, and worse filling accuracy. Furthermore, nozzle size moderates the impact of pump settings, surface tension, and viscosity on filling performance. Larger nozzles help mitigate these effects, contributing to enhanced stability in filling performance under challenging conditions. For high-concentration biopharmaceuticals with elevated viscosity during filling, utilizing larger nozzles and reducing pump speed could achieve enhanced Cpk values and improved filling accuracy. Understanding the complex interactions among these factors is vital for optimizing the biopharmaceutical industry, promoting cost-effective practices, and enhancing production efficiency.

Characterization and Inversion Method of Relative Permeability of Emulsion Flooding.

Relative permeability curves are one of the crucial factors that control the behavior of multiphase flow in petroleum reservoirs. Accurate prediction of the relative permeability curve involving emulsification and emulsion transport in emulsion flooding is vital to enhancing heavy oil recovery. In this study, a relative permeability characterization model including the emulsification mechanism and emulsion transport is developed, in which residual oil saturation and end-point permeability for water are parametrized as functions of emulsion concentration and capillary number. Based on the built characterization model, an inversion method (ensemble Kalman filter) is used to estimate the relative permeability curves of emulsion flooding. The inversion results of four sets of emulsion flooding experiments show that the errors of end points between the Johnson-Bossler-Neumann method and inversion method are less than 10%. For the continuous emulsification process in the in situ emulsion flooding tests, the inversed relative permeability curves shift between the upper and the inferior limits of the permeability. The error of residual oil saturation between the inversion and the experiment is less than 10%. In summary, this study demonstrates the feasibility of using the characterization model and inversion method to infer the relative permeability curves of emulsion flooding, which can aid in the predictions of multiphase flow in heavy oil reservoirs.

Effect of Fucoidan on Conformation of Xanthan Gum and Its Tribo-Rheological Properties.

This study sought to explore the rheological and tribological properties of fucoidan-xanthan gum (XG) mixtures at different fucoidan concentrations. A conformational transition of XG from disordered to ordered forms was observed with an increasing fucoidan concentration, as determined by intrinsic viscosity measurements and Fourier transform infrared analysis. All mixtures exhibited non-Newtonian flow behavior with the yield stress. The mixture sample with 0.5% fucoidan displayed higher apparent viscosity at 100 s-1, yield stress, and viscoelastic moduli values than XG alone, suggesting viscoelastic synergism between the two biopolymers. However, these values exhibited a decreasing trend with higher fucoidan concentrations (0.5-2.0%), indicating a nullification of synergism. While XG alone exhibited antithixotropic behavior, fucoidan-XG mixtures showed thixotropic behavior, most pronounced at 1.0% fucoidan. A decreasing trend was observed in the maximum friction coefficient as the fucoidan concentration increased, indicating better lubricant properties. Collectively, our findings may enable widespread adoption and application of fucoidan in various industries.

Wave basin investigation of floating wind turbine model using underwater particle image velocimetry: investigating hydrodynamic wake structures

This paper conducts a fundamental study on the hydrodynamic performance of a floating offshore wind turbine (FOWT). This includes investigating the impacts of platform motion, turbine operation, and environmental conditions on hydrodynamic wake development behind the FOWT. Using underwater particle image velocimetry in a wave basin, the fluid flow behaviour behind the floating wind substructure model is compared for different test configurations. The FOWT is examined in three configurations: I. Zero degrees of freedom (fixed), II. Six degrees of freedom (floating), and III. Floating with turbine in operation (full system). The results reveal significant hydrodynamic wake turbulence differences between fixed and floating systems, with 95% and 89% increases in turbulent kinetic energy (TKE) and turbulence intensity (TI), respectively. Turbine loading in configuration III results in additional damping and reduces eddy shedding, resulting in a 26% and 31% decrease in TKE and TI, compared to the floating configuration II. It is found that neglecting turbine operation overestimates substructure drag terms by at least 30%, while fixing the model underestimates drag terms by 54%. This study highlights a trade-off between model accuracy and dynamic complexity when estimating viscous effects on FOWT. It also provides a valuable set of high-fidelity validation data for the development of numerical tools for FOWT analysis.