A Numerical study on the hydrodynamic performance of an immersed foil: Uncertainty quantification of RANS and SPH methods

Ayyıldız, Murat; Saydam, Ahmet Ziya; Özbulut, Murat

doi:10.1016/j.compfluid.2019.104248

Cited by 7 publications

(2 citation statements)

References 41 publications

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“…In our previous study [26], the effects of the time step size or the maximum number of iterations per time step were not investigated. When considering higher particle resolution requirements of the WCSPH method at higher Reynolds numbers [34][35][36], our results have also pointed out the advantage of the ALSPH method over WCSPH in terms of computational costs, even without optimizing these temporal and iterative discretization parameters [26].…”

Section: Introductionmentioning

confidence: 60%

The Effect of Iterative Procedures on the Robustness and Fidelity of Augmented Lagrangian SPH

2021

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The Augmented Lagrangian Smoothed Particle Hydrodynamics (ALSPH) method is a novel incompressible Smoothed Particle Hydrodynamics (SPH) approach that solves Navier–Stokes equations by an iterative augmented Lagrangian scheme through enforcing the divergence-free coupling of velocity and pressure fields. This study aims to systematically investigate the time step size and the number of inner iteration parameters to boost the performance of the ALSPH method. Additionally, the effect of computing spatial derivatives with two alternative schemes on the accuracy of numerical results are also scrutinized. Namely, the first scheme computes spatial derivatives on the updated particle positions at each iteration, whereas the second one employs the updated pressure and velocity fields on the initial particle positions to compute the gradients and divergences throughout the iterations. These two schemes are implemented to the solution of a flow over a circular cylinder at Reynolds numbers of 200 in two dimensions. Initially, simulations are performed in order to determine the optimum time step sizes by utilizing a maximum number of five iterations per time step. Subsequently, the optimum number of inner iterations is investigated by employing the predetermined optimum time step size under the same flow conditions. Finally, the schemes are tested on the same flow problem with different Reynolds numbers using the best performing combination of the aforementioned parameters. It is observed that the ALSPH method can enable one to increase the time step size without deteriorating the numerical accuracy as a consequence of imposing larger ALSPH penalty terms in larger time step sizes, which, overall, leads to improved computational efficiency. When considering the hydrodynamic flow characteristics, it can be stated that two spatial derivative schemes perform very similarly. However, the results indicate that the derivative operation with the updated particle positions produces slightly lower velocity divergence magnitudes at larger time step sizes.

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Section: Introductionmentioning

confidence: 60%

The Effect of Iterative Procedures on the Robustness and Fidelity of Augmented Lagrangian SPH

2021

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“…As stated by the review by Violeau and Rogers [19], there are many SPH application research works that do not report the process of spatial resolution refinement. Although length scale refinement documentation is becoming a required standard practice, research works such as Altomare, et al [27], Ayyildiz, et al [28], Cui, et al [29], Yang, et al [30], and Yang, et al [31] only reported the particle spacing refinement process but did not mention the size of smoothing length being used. The majority of SPH application research reported particle spacing refinement study but only stated the values of smoothing length ratio without explicitly displaying the effect of changing this ratio on the results.…”

Section: Introductionmentioning

confidence: 99%

Exploration of Two Different Length Scale Refinement Strategies on the Application of SPH Simulations on 3D Free-surface Flows

Tran,

Roberts,

Hastie

2024

Preprint

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A length scale refinement study is a standard practice to ensure the independence of a numerical model on spatial approximations. For smoothed particle hydrodynamics (SPH), the process of length scale refinement study tends to be conducted based on experience. A challenge of defining a universal length scale refinement strategy is the existence of two length scales – particle spacing and smoothing length. Despite the challenge, further investigations of the impact of different refinement strategies should be continually conducted to improve the reliability of practical SPH applications on 3D free-surface flows. In this study, a conventional strategy and a novel coupled refinement strategy are used to investigate the convergence of SPH simulations for free-surface flows using a standard SPH scheme available in an open-source framework. The two case studies are a dam break flow and a lesser-known stable regime water flow inside a rotating drum with lifters. Validations are conducted using existing literature data for the dam break flow and laser Doppler velocimetry (LDV) measurements for the rotating drum flow. The investigation shows that the proposed coupled length scale refinement strategy does not offer a significant improvement for the SPH model of the dam break flow comparing to the conventional strategy. On the other hand, the stable regime rotating drum fluid flow shows that both refinement strategies are not sufficient to tackle SPH’s on-going fundamental challenge of accurately predicting the flow field of complex 3D turbulent flows with free surfaces.

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Development of computationally efficient augmented Lagrangian SPH for incompressible flows and its quantitative comparison with WCSPH simulating flow past a circular cylinder

Kolukısa

Özbulut

Peşman

et al. 2020

Numerical Meth Engineering

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SummaryIn Lagrangian particle‐based methods such as smoothed particle hydrodynamics (SPH), computing totally divergence‐free velocity field in a flow domain with the smallest error possible is the most critical issue, which might be achieved through solving pressure Poisson equation implicitly with higher particle resolutions. However, implicit solutions are computationally expensive and may be particularly challenging in the solution of multiphase flows with highly nonlinear deformations as well as fluid‐structure interaction problems. Augmented Lagrangian SPH (ALSPH) method is a new alternative algorithm as a prevalent pressure solver where the divergence‐free velocity field is achieved by iterative calculation of velocity and pressure fields. This study investigates the performance of the ALSPH technique by solving a challenging flow problem such as two‐dimensional flow around a cylinder within the Reynolds number range of 50 to 500 in terms of improved robustness, accuracy, and computational efficiency. The same flow conditions are also simulated using the conventional weakly compressible SPH (WCSPH) method. The results of ALSPH and WCSPH solutions are not only compared in terms of numerical validation/verification studies, but also rigorous investigations are performed for all related physical flow characteristics, namely, hydrodynamic coefficients, frequency domain analyses, and velocity divergence fields.

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A Numerical study on the hydrodynamic performance of an immersed foil: Uncertainty quantification of RANS and SPH methods

Cited by 7 publications

References 41 publications

The Effect of Iterative Procedures on the Robustness and Fidelity of Augmented Lagrangian SPH

The Effect of Iterative Procedures on the Robustness and Fidelity of Augmented Lagrangian SPH

Exploration of Two Different Length Scale Refinement Strategies on the Application of SPH Simulations on 3D Free-surface Flows

Development of computationally efficient augmented Lagrangian SPH for incompressible flows and its quantitative comparison with WCSPH simulating flow past a circular cylinder

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