Numerical Investigation on Large Scale Eddy Structure in Unsteady Pipe Elbow Flow at High Reynolds Number Conditions with Large Eddy Simulation Approach

Tanaka, Masaaki; Ohshima, Hiroyuki

doi:10.1299/jpes.6.210

Cited by 15 publications

(5 citation statements)

References 20 publications

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“…The above discussed process has in some degree a remote analogue. Those are the flows in tube turns [9][10][11]. But their studies touch circular tubes.…”

Section: Resultsmentioning

confidence: 99%

Acoustic signal control in disc vortex chamber of hydrodynamic cavitator

Ivanov

2021

20th International Scientific Conference Engineering for Rural Development Proceedings

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The use of acoustic cavitation processes permits to discover new ways to impact on product, to give unusual properties to liquids and their components, to create new technologies. In the vortex cavitators, which are used in this process, the acoustic field is created with a liquid whistle which looks like a disc vortex chamber. Though its design seems to be simple the liquid flows have a complicated structure. Some of these streams create the required acoustic field due to the competing interactions of two streams intersecting at an acute angle: the incoming stream and the peripheral stream. Peripheral flow is the earlier part of the incoming flow, which has completed almost a full revolution along the envelope. Another part of the flows interferes with the correct interaction and consumes energy. Moreover, when the flow from the tangential inlet pipe enters the cylindrical part of the vortex chamber, the effect the coming into corner takes place. Two conjugated toroidal vortices are formed along the shell. The parameters of the peripheral flow within the cycle are different; therefore, the nature of its interaction with the inlet flow is determined by the current phase of the cycle in the interaction zone. By adjusting the angle of ascent of the vortex components, their intensity, phase at the point of convergence of useful input and peripheral flows, it is possible to change the conditions of their interaction, the quality of the generated acoustic signal. The process of formation and development of vortex torus flows is shown, their intensity, both on a simplified analogue and on a disk-shaped vortex chamber. The places of interaction of the torus-shaped flow with the inner surface of the shell are determined, factors influencing the phase of the flow when it meets the inlet flow. The adequacy is proved by numerical methods based on solving the Navier-Stokes equations in the Flow vision software package.

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“…The above discussed process has in some degree a remote analogue. Those are the flows in tube turns [9][10][11]. But their studies touch circular tubes.…”

Section: Resultsmentioning

confidence: 99%

Acoustic signal control in disc vortex chamber of hydrodynamic cavitator

Ivanov

2021

20th International Scientific Conference Engineering for Rural Development Proceedings

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“…The capturing of these secondary flow features has been studied extensively by Takamura et al [98], Yuki et al [127], Tanaka and Ohshima [99] amongst others for the Japan Sodium cooled Fast Reactor (JSFR).…”

Section: Nuclear Applicationsmentioning

confidence: 99%

A Review of Embedded Large Eddy Simulation for Internal Flows

Holgate

Skillen

Craft

et al. 2018

Arch Computat Methods Eng

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When scale-resolving simulation approaches are employed for the simulation of turbulent flow, computational cost can often be prohibitive. This is particularly true for internal wall-bounded flows, including flows of industrial relevances which may involve both high Reynolds number and geometrical complexity. Modelling the turbulence induced stresses (at all scales) has proven to lack requisite accuracy in many situations. In this work we review a promising family of approaches which aim to find a compromise between cost and accuracy; hybrid RANS-LES methods. We place particular emphasis on the emergence of embedded large eddy simulation. These approaches are summarised and key features relevant to internal flows are highlighted. A thorough review of the application of these methods to internal flows is given, where hybrid approaches have been shown to offer significant benefits to industrial CFD (relative to an empirical broadband modelling of turbulence). This paper concludes by providing a cost-analysis and a discussion about the emerging novel use-modalities for hybrid RANS-LES methods in industrial CFD, such as automated embedded simulation and multi-dimensional coupling.

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“…On the contrary, there are very few studies available on pipe bend flow in the post-critical Reynolds numbers beyond R e = 4 Â 10 5 , where flow characteristics are likely to be independent of the Reynolds number (Iwamoto et al, 2012;Takamura et al, 2012;Dutta and Nandi, 2018). Numerical studies on bend flow at high Reynolds number condition have commenced recently (Tanaka and Ohshima, 2012;Kim et al, 2014;. These precedent studies were carried out on pipe bends of different bend curvature ratios (bend radius to diameter ratios) ranging from R c D = 1 to 5 and Reynolds numbers ranging from R e = (4.3 Â 10 4 to 10 Â 10 5 ).…”

Section: Introductionmentioning

confidence: 99%

PSO-tuned support vector machine metamodels for assessment of turbulent flows in pipe bends

Ganesh

Joshi

Dutta

et al. 2019

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Purpose Computational fluid dynamics (CFD) technique is the most commonly used numerical approach to simulate fluid flow behaviour. Owing to its computationally, cost-intensive nature CFD models may not be easily and quickly deployable. In this regard, this study aims to present a support vector machine (SVM)-based metamodelling approach that can be easily trained and quickly deployed for carrying out large-scale studies. Design/methodology/approach Radial basis function and ε^*-insensitive loss function are used as kernel function and loss function, respectively. To prevent overfitting of the model, five-fold cross-validation root mean squared error is used while training the SVM metamodel. Rather than blindly using any SVM tuning parameters, a particle swarm optimisation (PSO) is used to fine-tune them. The developed SVM metamodel is tested using various error metrics on disjoint test data. Findings Using the SVM metamodel, a parametric study is conducted to understand the effect of various factors influencing the behaviour of the turbulent fluid flow in the pipe bend with CFD simulation data set. Based on the parametric study carried out, it is seen that the diametric position has the most effect on dimensionless axial velocity, whereas Reynolds number has the least effect. Originality/value This paper provides an effective PSO-tuned SVM metamodelling approach, which may be used as a significant cost-saving approach to quickly and accurately estimate fluid flow characteristics that, in general, require the use of expensive CFD models.

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Numerical Investigation on Large Scale Eddy Structure in Unsteady Pipe Elbow Flow at High Reynolds Number Conditions with Large Eddy Simulation Approach

Cited by 15 publications

References 20 publications

Acoustic signal control in disc vortex chamber of hydrodynamic cavitator

Acoustic signal control in disc vortex chamber of hydrodynamic cavitator

A Review of Embedded Large Eddy Simulation for Internal Flows

PSO-tuned support vector machine metamodels for assessment of turbulent flows in pipe bends

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