Article
Computer Science, Interdisciplinary Applications
Wenyuan Chen, Shufan Zou, Qingdong Cai, Yantao Yang
Summary: In this study, a new technique is proposed to improve the calculation of the volume force representing the body boundary based on the moving-least-squares immersed boundary method. The error between the desired volume force and the actual force given by the original method is theoretically analyzed for boundaries with simple geometry. A spatially uniform coefficient is introduced to correct the force, and it can be determined by the least-square method over all boundary markers. The new method shows promising results in reducing boundary velocity residual and can be combined with the iterative method for further improvement.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Engineering, Multidisciplinary
Rafi Sela, Efi Zemach, Yuri Feldman
Summary: The extended immersed boundary methodology uses a semi-implicit direct forcing approach with a Schur complement method to enforce kinematic constraints for immersed surfaces in incompressible flow simulations. By utilizing parallel file systems for data handling, this methodology can be integrated into pressure-velocity segregated solvers for efficient computation. The methodology accurately meets the no-slip kinematic constraints on immersed oscillating bodies, as demonstrated in simulations of flows with out-of-phase oscillating spheres.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2021)
Article
Computer Science, Interdisciplinary Applications
Victor Cheron, Fabien Evrard, Berend van Wachem
Summary: A novel smooth immersed boundary method (IBM) based on a direct-forcing formulation is proposed for simulating incompressible dense particle-laden flows. This method uses a regularization technique to ensure the no-slip condition at particle surfaces by discretizing the transfer function between Eulerian grid points and Lagrangian markers. The approach, called hybrid IBM (HyBM), achieves more accurate results compared to classical IBM framework, especially at coarser mesh resolutions when particle surfaces or domain walls are close to Lagrangian markers.
COMPUTERS & FLUIDS
(2023)
Article
Computer Science, Interdisciplinary Applications
Panagiotis Tsoutsanis
Summary: This paper presents a family of stencil selection algorithms for WENO schemes on unstructured meshes. The paper focuses on evaluating the performance of various stencil selection algorithms and investigating the parameters that determine their robustness, accuracy, and computational efficiency. The goal is to develop efficient and robust stencil selection algorithms that can save computational resources while maintaining the non-oscillatory character of WENO schemes. Established test problems are used to assess the performance of the developed algorithms.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Computer Science, Interdisciplinary Applications
Rahul Bale, Amneet Pal Singh Bhalla, Boyce E. Griffith, Makoto Tsubokura
Summary: This paper introduces a one-sided immersed boundary (IB) method using kernel functions constructed via a moving least squares (MLS) method, which effectively reduces spurious feedback forcing and internal flows observed in traditional IB models. The method extends the original MLS methodology, proposes ways to construct one-sided kernel functions, and suggests strategies for constructing positive and monotone functions to enhance stability. Benchmark cases are used to test accuracy and verify simulations in both two and three spatial dimensions, demonstrating its applicability for modeling complex engineering flows.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Computer Science, Interdisciplinary Applications
Pedro M. P. Costa, Duarte M. S. Albuquerque
Summary: In this paper, a new operator is proposed to convert point values into mean ones, enabling simpler high-order spatial schemes for unsteady problems. The method is verified for different orders and grid types, and the numerical spatial error evolution, solver runtime, and memory requirement are compared as efficiency metrics. The results show that high-order schemes provide faster and more accurate results compared to second-order schemes.
JOURNAL OF COMPUTATIONAL PHYSICS
(2022)
Article
Mathematics, Applied
Joseph Lifton, Tong Liu, John McBride
Summary: Algorithms for linear and non-linear least squares fitting of Bezier surfaces to unstructured point clouds are derived, with a quantitative comparison made between fitting Bezier surfaces and polynomial surfaces, as well as using the fitting algorithm to remove the geometric form of complex engineered surfaces for evaluation of surface roughness.
Article
Computer Science, Interdisciplinary Applications
Benjamin Constant, Stephanie Peron, Heloise Beaugendre, Christophe Benoit
Summary: The paper presents recent improvements of an Immersed Boundary Method (IBM) for simulating turbulent compressible flows on Cartesian grids, showing its effectiveness through comparison with a body-fitted approach.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Computer Science, Interdisciplinary Applications
Xiang Zhao, Zhen Chen, Liming Yang, Ningyu Liu, Chang Shu
Summary: In this study, the original boundary condition-enforced immersed boundary method is improved with the use of conjugate gradient technique and explicit technique for simulating incompressible flows with moving boundaries. The computational efficiency of the improved IBM is demonstrated to be higher than other popular IBM methods, especially the explicit technique-based IBM with a linear computational complexity. Coupled with D1Q4 lattice Boltzmann flux solver, the IBM with conjugate gradient technique and explicit technique successfully simulate two-dimensional and three-dimensional flows with second order accuracy in space.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Computer Science, Interdisciplinary Applications
Marin Lauber, Gabriel D. Weymouth, Georges Limbert
Summary: Immersed boundary methods are widely used for simulating interactions between dynamic solid objects and fluids due to their computational efficiency and modeling flexibility. However, thin geometries often violate the boundary conditions in existing immersed boundary projection algorithms. This study proposes a minimal thickness modification for the Boundary Data Immersion Method (BDIM-sigma) to address this issue and improve the accuracy of high-speed immersed surface simulations.
JOURNAL OF COMPUTATIONAL PHYSICS
(2022)
Article
Computer Science, Interdisciplinary Applications
Shang-Gui Cai, Johan Degrigny, Jean-Francois Boussuge, Pierre Sagaut
Summary: An improved coupling method of immersed boundary method and turbulence wall models on Cartesian grids is proposed to generate smooth wall surface pressure and skin friction at high Reynolds numbers. Various modifications are presented to enhance the near wall solution, and the validity of the method is demonstrated through numerical benchmark tests.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Computer Science, Interdisciplinary Applications
Antoine Michael Diego Jost, Stephane Glockner
Summary: The article proposes linear/quadratic square shifting methods to improve the accuracy and convergence of ghost-cell immersed boundary methods for Cartesian grids. The methods aim to increase the order of convergence while maintaining a maximum stencil size of 2, and are evaluated through a comprehensive verification and validation process.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Computer Science, Interdisciplinary Applications
Simon Gsell, Julien Favier
Summary: The study analyzed the boundary slip error caused by the interpolation/spreading non-reciprocity of the direct-forcing immersed-boundary method, and proposed a correction method to improve the no-slip condition without requiring additional computational time or implementation effort. This a priori correction significantly enhanced the accuracy of the method.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Mathematics, Interdisciplinary Applications
Sambit Majumder, Arnab Ghosh, Dipankar Narayan Basu, Ganesh Natarajan
Summary: In this study, we investigate the accuracy and robustness of our in-house OpenMP parallelized direct-forcing immersed boundary-lattice Boltzmann (DF-IB-LB) solver. We find that the solver exhibits first and second-order spatial accuracy for velocity and pressure errors, respectively, for generic moving boundary problems. The method is Galilean invariant, and errors in discrete conservation and spurious force oscillations decay linearly and superlinearly, respectively, with grid refinement.
COMPUTATIONAL PARTICLE MECHANICS
(2023)
Article
Mathematics, Applied
Ashwani Assam, Ganesh Natarajan
Summary: A new second-order accurate finite volume scheme for diffusion equations with discontinuous coefficients on unstructured meshes is proposed in the paper. This scheme is based on least squares reconstruction and the concept of alpha damping for linear exactness, with two variants introduced for different conditions to improve the accuracy of the solution. Numerical experiments show that these schemes are capable of estimating the solution and fluxes accurately on generic polygonal meshes, and are discrete extremum preserving.
COMPUTERS & MATHEMATICS WITH APPLICATIONS
(2021)
Article
Energy & Fuels
Pablo Ouro, Paul Dene, Patxi Garcia-Novo, Tim Stallard, Yusaku Kyozuda, Peter Stansby
Summary: Tidal and wind energy projects primarily use horizontal axis turbines (HATs), while vertical axis turbines (VATs) have limited deployment due to their lower technology readiness level. This paper analyzes the power density of HATs and VATs with different height-to-diameter ratios and turbine spacing at three real tidal sites. The results show that HATs are more suitable for highly energetic sites, while VATs provide higher power densities at sites with low-to-medium velocities. Additionally, VATs with height-to-diameter ratios larger than three can significantly reduce wake effects and achieve high average power density.
JOURNAL OF OCEAN ENGINEERING AND MARINE ENERGY
(2023)
Article
Computer Science, Interdisciplinary Applications
Panagiotis Tsoutsanis, Xesus Nogueira, Lin Fu
Summary: This article proposes two techniques for computing consistent energy spectra for 3D unstructured meshes with different element types. These techniques are particularly useful for assessing dissipation characteristics and suitability of non-linear high-order methods for implicit large-eddy simulations (iLES). Numerical experiments show the performance of various element types for iLES of the Taylor-Green vortex, revealing significantly different dissipation and dispersion mechanisms for each element type. The energy spectra results depend on the selected technique, and a comparison with an established technique from the literature is included to analyze their similarities and differences. These techniques are integral for tuning and calibrating non-linear high-order methods in both explicit and implicit large-eddy simulations (LES).
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Physics, Fluids & Plasmas
Valentine Muhawenimana, Nadine Foad, Pablo Ouro, Catherine A. M. E. Wilson
Summary: The performance of cable flow-altering bed scour countermeasures was evaluated through experiments. The reduction of scour depth, changes in bed morphology, and effects on the flow field were assessed. Cables protected the pier from scour, reducing the scour depth by up to 52%. The presence of the cables also altered the flow within the scour hole and reduced vortex shedding frequency in the pier wake.
Article
Mathematics, Applied
Luis Ramirez, Laura Edreira, Ivan Couceiro, Pablo Ouro, Xesus Nogueira, Ignasi Colominas
Summary: In this paper, a new arbitrary-order Finite Volume method is proposed for the numerical solution of the Euler and Navier-Stokes equations on unstructured grids. The method achieves arbitrary order using a modified Moving Least Squares reconstruction, which preserves the mean values of the conservative variables. The proposed scheme's accuracy and performance are assessed using several benchmark problems, demonstrating the achievement of arbitrary order of convergence. Furthermore, the method is applied to simulate turbulent flows solved by the Navier-Stokes equations.
APPLIED MATHEMATICS AND COMPUTATION
(2023)
Article
Computer Science, Interdisciplinary Applications
Fawaz Alzabari, Catherine A. M. E. Wilson, Pablo Ouro
Summary: The turbulent wake generated by a horizontal circular cylinder in increasingly shallow free-surface flows is investigated using large-eddy simulation. The proximity of the cylinder to the bottom wall generates an asymmetric von-Karman vortex street, with the coherence of the vortex shedding affected by the drop in the free-surface downstream. The energy content and frequency of the turbulent structures shed in the cylinder wake are affected by the shallowness of the flow.
COMPUTERS & FLUIDS
(2023)
Article
Engineering, Civil
G. Garcia-Alen, R. Hostache, L. Cea, J. Puertas
JOURNAL OF HYDROLOGY
(2023)
Article
Meteorology & Atmospheric Sciences
Karim Ali, David m. Schultz, Alistair Revell, Timothy Stallard, Pablo Ouro
Summary: To simulate the large-scale impacts of wind farms, parameterizations of wind turbines were implemented in the Weather Research and Forecasting (WRF) Model v4.3.3. Simulation results were verified against various measurements for operational wind farms in the North Sea. The different parameterizations showed variations in the prediction of turbulence, wind speed deficits, and power generation, highlighting the need for improved prediction of near-surface wind speed, temperature, and turbulence in wind-farm parameterizations. The study also revealed that wakes from offshore wind farms can extend significant distances and reduce downwind power production.
MONTHLY WEATHER REVIEW
(2023)
Article
Green & Sustainable Science & Technology
M. Manolesos, L. Chng, N. Kaufmann, P. Ouro, D. Ntouras, G. Papadakis
Summary: Tidal energy can play a crucial role in the Net Zero transition, and the innovation of tidal turbine performance is important for its cost competitiveness. This proof-of-concept study demonstrates the potential of using passive Vortex Generators (VGs) to improve the performance of tidal turbine blades and reduce flow separation. The study includes wind tunnel experiments and numerical simulations, showing that low profile VGs shorter than the local boundary layer can successfully increase the blade profile performance and suppress flow separation. This study is the first to explore the inclusion of passive VGs in the design or retrofitting of tidal turbine blades.
Review
Environmental Sciences
J. Lofty, P. Ouro, C. A. M. E. Wilson
Summary: Current sampling approaches for quantifying microplastics (MP) in riverine systems are unstandardized and lack important river properties, hindering our understanding of MP behavior. In this study, we reviewed 36 field-based river studies and found that most studies did not meet quality criteria and omitted critical information. However, spatial information and sampling equipment were adequately documented in many studies. A standardized sampling approach is proposed to improve our understanding of MP behavior and transport in freshwater environments. Additionally, a meta-analysis revealed high variability in MP concentrations and identified commonly reported polymers and shapes in river studies.
SCIENCE OF THE TOTAL ENVIRONMENT
(2023)
Article
Multidisciplinary Sciences
Stephanie Mueller, Valentine Muhawenimana, Guglielmo Sonnino-Sorisio, Catherine A. M. E. Wilson, Joanne Cable, Pablo Ouro
Summary: Vertical axis turbines (VATs) can provide decentralized, clean, and sustainable energy for remote communities. This study investigates the effects of VATs on fish movement and finds that fish can swim around and through the turbine even under different flow rates, turbine operation states, and cross-sectional confinements. However, fish tend to avoid the turbine's vicinity and wake, indicating low-risk behavior. These findings contribute to the understanding of VATs as a renewable energy solution for remote communities in rivers, estuaries, or the sea.
SCIENTIFIC REPORTS
(2023)
Review
Computer Science, Interdisciplinary Applications
Antonio Eiris, Luis Ramirez, Ivan Couceiro, Javier Fernandez-Fidalgo, Jose Paris, Xesus Nogueira
Summary: This paper provides a review of the meshless-FV family of methods and analyzes the MLS-SPH-ALE method as a general formulation that relates to both particle-based and finite volume methods. The MLS-SPH-ALE method is a versatile approach that addresses consistency issues caused by kernel approximation.
ARCHIVES OF COMPUTATIONAL METHODS IN ENGINEERING
(2023)
Article
Engineering, Environmental
J. Lofty, D. Valero, C. A. M. E. Wilson, M. J. Franca, P. Ouro
Summary: Microplastic pollution poses a known threat to aquatic and terrestrial ecosystems, but the mechanisms of MP transport in rivers remain unknown. Laboratory experiments comparing MP and natural sediment transport dynamics reveal similarities and only a few differences in saltation trajectory and collision angles. Overall, spherical MP particles behave similarly to spherical natural sediments in aquatic environments under the examined conditions, providing a foundation for further studies on MP transport.
Article
Computer Science, Interdisciplinary Applications
Ashish Bhole, Herve Guillard, Boniface Nkonga, Francesca Rapetti
Summary: Finite elements of class C-1 are used for computing magnetohydrodynamics instabilities in tokamak plasmas, and isoparametric approximations are employed to align the mesh with the magnetic field line. This numerical framework helps in understanding the operation of existing devices and predicting optimal strategies for the international ITER tokamak. However, a mesh-aligned isoparametric representation encounters issues near critical points of the magnetic field, which can be addressed by combining aligned and unaligned meshes.
INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS
(2024)
Article
Computer Science, Interdisciplinary Applications
Federico Vismara, Tommaso Benacchio
Summary: This paper introduces a method for solving hyperbolic-parabolic problems on multidimensional semi-infinite domains. By dividing the computational domain into bounded and unbounded subdomains and coupling them using numerical fluxes at the interface, accurate numerical solutions are obtained. In addition, computational cost can be reduced by tuning the parameters of the basis functions.
INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS
(2024)
Article
Computer Science, Interdisciplinary Applications
Keigo Enomoto, Takato Ishida, Yuya Doi, Takashi Uneyama, Yuichi Masubuchi
Summary: We have developed a novel Moving Particle Simulation (MPS) method to accurately reproduce the motion of fibers in sheared liquids. By introducing the micropolar fluid model, we address the issue of fibers being aligned with the flow direction in conventional MPS simulations. Our method is capable of accurately reproducing the fiber motion predicted by Jeffery's theory.
INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS
(2024)
