Unsteady Flow Characteristics in a 90 Degree Elbow Affected by Developed, Undeveloped and Swirling Inflow Conditions

Iwamoto, Yukiharu; Kondo, Manabu; Minamiura, Hirotaka; Tanaka, Masaaki; Yamano, Hidemasa

doi:10.1299/jfst.7.315

Cited by 12 publications

(4 citation statements)

References 18 publications

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“…The difference probably is caused by whether the flow separation occurs or not. Our previous LDV velocity measurements under the case of R e = 3.2 × 10 5 has shown the flow separation in the downstream region of the elbow (Iwamoto, et al, 2012). Fig.…”

Section: Experimental Methodsmentioning

confidence: 68%

“…Comparison with results of the 1/3 scale model shows that all the data but at the elbow inside (ϕ = 0˚) have spectral peaks with S t = 0.5, and all the magnitude with respect to these peaks are the same. The spectral peaks with S t = 0.5 are excited by vortices shed from circumferential edges of the boundary layer at the elbow inside (Iwamoto, et al, 2012). Values of this phenomenon can be summarized as one when nondimensionalized by the bulk velocity and elbow inner diameter.…”

Section: Experimental Methodsmentioning

confidence: 99%

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Unsteady wall pressure characteristics of a 90 degree elbow in high Reynolds numbers

Iwamoto

Yamano

2014

JFST

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Section: Experimental Methodsmentioning

confidence: 68%

Section: Experimental Methodsmentioning

confidence: 99%

Unsteady wall pressure characteristics of a 90 degree elbow in high Reynolds numbers

Iwamoto

Yamano

2014

JFST

Self Cite

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“…1. There have been several investigations on the flow inside and downstream of a 90 • bend, ranging from CFD [18][19][20][21][22][23][24][25] to experimental studies [26][27][28][29][30]. Most of the investigations mainly focus on the flow inside or in the vicinity of the bend.…”

Section: Introductionmentioning

confidence: 99%

Hybrid LES/RANS simulations of a 90° pipe bend using different CFD solvers

Ekat,

Weissenbrunner,

Straka

et al. 2023

OpenFOAM J

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In this study, the performance of several RANS and hybrid LES/RANS turbulence models along with different CFD solvers (ANSYS Fluent, OpenFOAM and RapidCFD) is tested in terms of their ability to reproduce the flow downstream of a 90° pipe bend. The focus is on the temporal mean profiles downstream of the bend up to approximately 31 times the pipe's diameter D. The turbulence models' accuracy is evaluated by means of performance indicators and flow profiles in comparison to LDA measurements. The results demonstrate that the use of RANS models is suitable as long as the location of interest is in the vicinity of the bend up to approximately 10 D downstream of the bend. With increasing distance, the accuracy of the RANS models decreases, and the use of hybrid LES/RANS models is recommended.Three hybrid LES/RANS models are tested: the stress-blended eddy simulation (SBES) model as well as the Spalart-Allmaras-based and the k-omega SST-based improved delayed detached eddy simulation (IDDES) models. All three models show enhanced results for a distance to the bend >10 D. Additionally, it is found that in this geometry configuration, the IDDES models require a transient inlet. The flow separation due to the redirection inside the bend is too weak to generate turbulent fluctuations and a fast transition to full LES mode in the separation region. Due to the turbulent excitation at the inlet, the RANS region downstream of the bend is distinctly reduced, resulting in an enhanced performance of the hybrid IDDES models.

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“…In the past few decades, the mean flow and turbulence measurements in the curved pipe were mainly conducted at moderate Reynolds numbers, R e = (4 -8)Â10 4 (Sudo et al, 1998;Iwamoto et al, 2012;Mazhar et al, 2016;Taguchi et al, 2018). 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;.…”

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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Unsteady Flow Characteristics in a 90 Degree Elbow Affected by Developed, Undeveloped and Swirling Inflow Conditions

Cited by 12 publications

References 18 publications

Unsteady wall pressure characteristics of a 90 degree elbow in high Reynolds numbers

Unsteady wall pressure characteristics of a 90 degree elbow in high Reynolds numbers

Hybrid LES/RANS simulations of a 90° pipe bend using different CFD solvers

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

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