| 1. |
- Bobke, Alexandra, et al.
(author)
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Turbulent asymptotic suction boundary layers : Effect of domain size and development time
- 2016
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In: Springer Proceedings in Physics. - Cham : Springer. - 9783319291291 ; , s. 173-177
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Conference paper (peer-reviewed)abstract
- A series of large-eddy simulations of a turbulent asymptotic suction boundary layer (TASBL) was performed in a periodic domain, on which uniform suction was applied over a flat plate. The Reynolds number (defined as the ratio between free-stream and suction velocity) was Re=333" role="presentation" style="border: 0px; font-variant: inherit; font-stretch: inherit; line-height: normal; font-family: inherit; margin: 0px; padding: 0px; vertical-align: baseline; outline: 0px; display: inline; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; position: relative;">Re=333Re=333and a variety of domain sizes were considered in temporal simulations in order to investigate the effect of the computational domain size and temporal development length. The asymptotic state is related to high friction Reynolds numbers and was found to require large computational domains and development lengths.
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| 2. |
- Brandt, Luca, et al.
(author)
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Turbulent flow of a suspension of rigid spherical particles in plane channels
- 2016
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In: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 9783319291291 ; , s. 311-315
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Conference paper (peer-reviewed)abstract
- Suspensions of solid particles are frequently found in applications and environmental flows. Several studies concern the rheological properties of suspensions in laminar flows, but much less is known of turbulent suspensions. The present work fills this gap providing DNS data on dense suspensions of neutrally-buoyant rigid sphere in a turbulent channel flow at the bulk Reynolds number of Re = U0h/ν = 2800. We show that considering volume fractions Φ ≤ 0.1 the turbulent flow is similar to the unladen case with higher turbulence intensities. On the contrary, the flow behavior strongly changes at Φ = 0.2where the turbulence appears to be attenuated.
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| 3. |
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| 4. |
- Skote, Martin, et al.
(author)
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Wall oscillation induced drag reduction of turbulent boundary layers
- 2016
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In: Springer Proceedings in Physics. - Cham : Springer. - 9783319291291 ; , s. 161-165
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Conference paper (peer-reviewed)abstract
- Spanwise oscillation applied on the wall under a turbulent boundary layer flow is investigated using direct numerical simulation. The temporal wall-forcing produces considerable drag reduction over the region where oscillation occurs. The turbulence fluctuations downstream of the oscillations are presented for the first time. Simulations with identical oscillation parameters have been performed at different Reynolds numbers to investigate the effect on the drag reduction. One of the simulations replicates an earlier experiment to test the fidelity of the current simulations. In addition, we present the future work in this area with an integrated experimental and computational investigation to explore the possibility of applying travelling waves (oscillations in both time and space) as the mode of wall motion for active control of near-wall turbulence.
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| 5. |
- Talamelli, A., et al.
(author)
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Temperature effects in hot-wire measurements on higher-order moments in wall turbulence
- 2016
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In: Springer Proceedings in Physics. - Cham : Springer. - 9783319291291 ; , s. 185-189
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Conference paper (peer-reviewed)abstract
- The effect of temperature fluctuations—as they are e.g. encountered in non-isothermal flows—on the mean, variance and spectra in wall-bounded turbulent flows when utilising hot-wire anemometry has recently been documented. The present work extends these efforts on the effect of temperature fluctuations on the skewness and flatness factors as well as assesses the performance of commonly employed temperature compensations.
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| 6. |
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| 7. |
- Vinuesa, Ricardo, et al.
(author)
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Flow features in three-dimensional turbulent duct flows with different aspect ratios
- 2016
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In: Springer Proceedings in Physics. - Cham : Springer. - 9783319291291 ; , s. 123-126
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Conference paper (peer-reviewed)abstract
- Direct numerical simulations of turbulent duct flows with width-to-height ratios 1, 3, 5, 7 and 10, at a friction Reynolds number Reτ,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 = (V2 + W2)/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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