New insight into flow development and two dimensionality of turbulent channel flows

Vinuesa, Ricardo; Bartrons, Eduard; Chiu, Daniel T.; Dressler, Kristofer; Rüedi, Jean-Daniel; Suzuki, Yasuyuki; Nagib, Hassan

doi:10.1007/s00348-014-1759-8

Cited by 28 publications

(19 citation statements)

References 22 publications

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“…These errors are lower than the ones reported in other studies in the literature, where the correlations among parameters are not considered. To provide some examples, uncertainties of 0.85% and 0.58% were reported by Vinuesa et al [58] for τ w and u τ , respectively; Segalini et al [48] obtained an uncertainty of around 0.5% in u τ and a larger uncertainty in δ ν , 1.9%, was reported by Bailey et al [3]. These results highlight the importance of accounting for such correlations when determining the overall uncertainty.…”

Section: Summary and Concluding Remarksmentioning

confidence: 71%

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Assessment of uncertainties in hot-wire anemometry and oil-film interferometry measurements for wall-bounded turbulent flows

Rezaeiravesh

Vinuesa

Liefvendahl

et al. 2018

European Journal of Mechanics - B/Fluids

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In this study, the sources of uncertainty of hot-wire anemometry (HWA) and oil-film interferometry (OFI) measurements are assessed. Both statistical and classical methods are used for the forward and inverse problems, so that the contributions to the overall uncertainty of the measured quantities can be evaluated. The correlations between the parameters are taken into account through the Bayesian inference with error-in-variable (EiV) model. In the forward problem, very small differences were found when using Monte Carlo (MC), Polynomial Chaos Expansion (PCE) and linear perturbation methods. In flow velocity measurements with HWA, the results indicate that the estimated uncertainty is lower when the correlations among parameters are considered, than when they are not taken into account. Moreover, global sensitivity analyses with Sobol indices showed that the HWA measurements are most sensitive to the wire voltage, and in the case of OFI the most sensitive factor is the calculation of fringe velocity. The relative errors in wall-shear stress, friction velocity and viscous length are 0.44%, 0.23% and 0.22%, respectively. Note that these values are lower than the ones reported in other wall-bounded turbulence studies. Note that in most studies of wall-bounded turbulence the correlations among parameters are not considered, and the uncertainties from the various parameters are directly added when determining the overall uncertainty of the measured quantity. In the present analysis we account for these correlations, which may lead to a lower overall uncertainty estimate due to error cancellation. Furthermore, our results also indicate that the crucial aspect when obtaining accurate inner-scaled velocity measurements is the wind-tunnel flow quality, which is more critical than the accuracy in wall-shear stress measurements. 1

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Section: Summary and Concluding Remarksmentioning

confidence: 71%

“…The OFI dataset was obtained from the channel-flow measurements described in Ref. [58]. This dataset includes the oil calibration data, the camera angle and oil refractive index, together with a series of oilfringe pictures corresponding to one of the measurements.…”

Section: Uncertainties In Hwa and Ofi Measurementsmentioning

confidence: 99%

Assessment of uncertainties in hot-wire anemometry and oil-film interferometry measurements for wall-bounded turbulent flows

Rezaeiravesh

Vinuesa

Liefvendahl

et al. 2018

European Journal of Mechanics - B/Fluids

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“…A large number of irregular small vortexes will replace the spiral vortex belt, and the signal exhibits a noise-like broadband characteristic, which can be seen in the spectrum analysis of tested signal in the following section [31]. Samanta and Vinuesa et al also studied the characterizations of the flow field through numerical simulations and experiments [32][33][34]. In the other hand, the preliminary tests results also prove the consistency of each unit as vibration source.…”

Section: Preliminary Tests Resultsmentioning

confidence: 78%

Study on Vibration Transmission among Units in Underground Powerhouse of a Hydropower Station

Lian

Wang

2018

Energies

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Research on the safety of powerhouse in a hydropower station is mostly concentrated on the vibration of machinery structure and concrete structure within a single unit. However, few studies have been focused on the vibration transmission among units. Due to the integrity of the powerhouse and the interaction, it is necessary to study the vibration transmission mechanism of powerhouse structure among units. In this paper, field structural vibration tests are conducted in an underground powerhouse of a hydropower station on Yalong River. Additionally, the simplified mechanical models are established to explain the transmission mechanism theoretically. Moreover, a complementary finite element (FE) model is built to replicate the testing conditions for comprehensive analysis. The field tests results show that: (1) the transmission of lateral-river vibration is greater than those of longitude-river vibration and vertical vibration; (2) the vibration transmission of the vibrations that is caused by the low frequency tail fluctuation is basically equal to that of the vibrations caused by rotation of hydraulic generator. The transmission mechanism is demonstrated by the simplified mechanical models and is verified by the FE results. This study can provide guidance for further research on the vibration of underground powerhouse structure.

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“…However, the dynamics of the turbulence and short-time averages of the vortical flow have revealed differences in the core region between the channel and ducts with aspect ratios up to 10 [6]. This suggests that experimental facilities intended to represent the canonical channel flow and to compare the turbulence structures and dynamics and vortical flow details may require aspect ratios larger than facilities with highest ratios used so far of 12 and may need to be as large as 18, as in [7].…”

Section: Results and Conclusionmentioning

confidence: 94%

Flow Features in Three-Dimensional Turbulent Duct Flows with Different Aspect Ratios

Vinuesa¹,

Schlatter²,

Nagib

2016

Springer Proceedings in Physics

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Direct numerical simulations of turbulent duct flows with width-to-height ratios 1, 3, 5, 7 and 10, at a friction Reynolds number Re τ,c 180, are carried out with the spectral element code Nek5000. The aim of these simulations is to gain insight into the kinematics and dynamics of Prandtl's secondary flow of second kind, and its impact on the flow physics of wall-bounded turbulence. The secondary flow is characterized in terms of the cross-plane mean kinetic energy K = V 2 + W 2 /2, and its variation in the spanwise direction of the flow. Our results show that averaging times of at least 3,000 time units are required to reach a converged state of the secondary flow, which extends up to z * 5 h from the side walls. We also show that if the duct is not wide enough to accommodate the whole extent of the secondary flow, then its structure is modified by means of a different spanwise distribution of energy. Future proposed work includes coherent structure eduction, quadrant analysis at the corner, and comparisons with spanwise-periodic channels at comparable Reynolds numbers.

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New insight into flow development and two dimensionality of turbulent channel flows

Cited by 28 publications

References 22 publications

Assessment of uncertainties in hot-wire anemometry and oil-film interferometry measurements for wall-bounded turbulent flows

Assessment of uncertainties in hot-wire anemometry and oil-film interferometry measurements for wall-bounded turbulent flows

Study on Vibration Transmission among Units in Underground Powerhouse of a Hydropower Station

Flow Features in Three-Dimensional Turbulent Duct Flows with Different Aspect Ratios

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