Computational study of incompressible turbulent flows with method of characteristics

Orang, Ali Atashbar; Razavi, Seyed Esmail; Pourmirzaagha, Hamoon

doi:10.1016/j.cam.2013.05.019

Cited by 3 publications

(3 citation statements)

References 22 publications

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“…Research has included multifluid flows [74,75], compressible flow [76], incompressible flow [77], shear-thickening and shear-thinning fluids [78], and a link-wise discretization similar to Lattice-Boltzmann methods [79]. Foundations for characteristic-based methods were developed as an an early part of this work [80][81][82], and have been studied for higher accuracy discretizations [83,84]. A relatively new addition has been an entropically-damped formulation [85], which substitutes a thermodynamic approximation for the simple artificial compressibility of Chorin [27].…”

Section: Recent Development Of the Artificial Compressibility Methodsmentioning

confidence: 99%

“…Indeed, a global γ = 1 is often a default in artificial compressibility studies (e.g., [30,56,122,123]), although higher values are also found (e.g., [62,78,124]). A wide range of studies fail to document the values used for γ; likely because it formally controls convergence rates rather than accuracy (e.g., [73,77,81,83,120])-although it can also affect the simulation result for upwind schemes [124]. Methods have been developed to select an optimum global γ based on flow characteristics and/or model time step (e.g., [63,64,[125][126][127]), or using mesh spacing [72], or as a preconditioning parameter for a solution matrix [128].…”

Section: Choosing An Artificial Speed Of Soundmentioning

confidence: 99%

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An Artificial Compressibility Method for 1D Simulation of Open-Channel and Pressurized-Pipe Flow

Hodges

2020

Water

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Piping systems (e.g., storm sewers) that transition between free-surface flow and surcharged flow are challenging to model in one-dimensional (1D) networks as the continuity equation changes from hyperbolic to elliptic as the water surface reaches the pipe ceiling. Previous network models are known to have poor mass conservation or unpredictable convergence behavior at such transitions. To address this problem, a new algorithm is developed for simulating unsteady 1D flow in closed conduits with both free-surface and surcharged flow. The shallow-water (hydrostatic) approximation is used as the governing equations. The artificial compressibility (AC) method is implemented as a dual-time-stepping discretization for a finite-volume solver with timescale interpolation used for face reconstruction. A new formulation for the AC celerity parameter is proposed such that the AC celerity matches the equivalent gravity wave speed for the local hydraulic head—which has some similarities to the classic Preissmann Slot used to approximate pressurized flow in conduits. The new approach allows the AC celerity to be set locally by the flow (i.e., non-uniform in space) and removes it as a free parameter of the AC solution method. The derivation of the AC method provides for only a minor change in the form of the solution equations when a computational element switches from free-surface to surcharged. The new solver is tested for both unsteady free-surface (supercritical, subcritical) and surcharged flow transitions in a circular pipe and is implemented in an open-source Python code available under the name “PipeAC.” The results are compared to laboratory experiments that include rapid flow changes due to opening/closing of gates. Results show that the new algorithm is satisfactory for 1D representation of unsteady transition behavior with two caveats: (i) sufficient grid resolution must be applied, and (ii) the shallow-water equation approximations (hydrostatic, single-fluid) limit the accuracy of the solution with regards to the celerity of the turbulent unsteady bore that propagates upstream. This research might benefit any piping network model that must smoothly handle unsteady transitions from free surface to surcharged flow.

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Section: Recent Development Of the Artificial Compressibility Methodsmentioning

confidence: 99%

Section: Choosing An Artificial Speed Of Soundmentioning

confidence: 99%

An Artificial Compressibility Method for 1D Simulation of Open-Channel and Pressurized-Pipe Flow

Hodges

2020

Water

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“…More progresses relating to the important influences caused by flow models on the AWJ characteristic determinations can be found from (Atashbar Orang, Razavi, & Pourmirzaagha, 2014;Cui, An, Mao, & Li, 2009;Kumar Pal & Choudhury, 2014;Lebar, Junkar, Poredoš, Cvjeticanin, 2010). After introducing the idea of fuzzy prediction, we can see that more researchers began paying their high attentions on this new method, since it returns an accurate and stable prediction result from miscellaneous data sets.…”

Section: Introductionmentioning

confidence: 99%

Fuzzy prediction of AWJ turbulence characteristics by using typical multi-phase flow models

Liang

Shan

Liu

et al. 2017

Engineering Applications of Computational Fluid Mechanics

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For the purpose of improving the working performance of AWJ (Abrasive waterjet) grinding in actual machining, and revealing the unknown influence mechanism of waterjet machining prediction, this research conducted a theoretical and experimental investigation concerning with the influences caused by multi-phase flow models, on the fuzzy prediction of turbulence characteristics. First, typical flow models describing the abrasive waterjet were presented and enunciated; Second, a series of turbulence characteristics were defined to quantitatively demonstrate the waterjet flow, which are responsible for the actual performances of AWJ grinding in the contact zone; Then a new fuzzy prediction system equipped with logic protocols was established and introduced to predict turbulence characteristics based upon the machining parameters by employing different flow models, therefore a set of quantified prediction results generated from the CFD (Computational Fluid Dynamics) simulation, orthogonal experiments and actual measurements can be obtained and distinguished systematically. Through a detailed performance analysis with benchmark indexes and prediction comparisons, the theoretical superiorities and specific applications of these flow models were fully discussed and then an integrated conclusion assessing their inherent influence mechanism was acquired. Based on these innovative achievements, the instantaneous machining inspection or parameter optimization in AWJ grinding process can be facilitated, simultaneously the new research ideas aimed at waterjet monitoring or grinding improvements can be presented as well. ARTICLE HISTORY

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Genuinely characteristic-based scheme for the incompressible turbulent flows

Orang

2014

Computers & Fluids

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Computational study of incompressible turbulent flows with method of characteristics

Cited by 3 publications

References 22 publications

An Artificial Compressibility Method for 1D Simulation of Open-Channel and Pressurized-Pipe Flow

An Artificial Compressibility Method for 1D Simulation of Open-Channel and Pressurized-Pipe Flow

Fuzzy prediction of AWJ turbulence characteristics by using typical multi-phase flow models

Genuinely characteristic-based scheme for the incompressible turbulent flows

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