Experimental study of secondary flows above rough and flat interfaces in horizontal gas-liquid pipe flow

Vollestad, Petter; Angheluta, Luiza; Jensen, Atle

doi:10.1016/j.ijmultiphaseflow.2020.103235

Cited by 13 publications

(10 citation statements)

References 31 publications

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“…Fundamentally, a partially filled pipe flow, a gravity-driven open-channel flow, is different from the pressure-driven flow of a fully filled pipe. One significant difference is the presence of secondary currents in a partially filled pipe flow, due to a non-circular fluid cross-sectional area (Prandtl 1926; Bradshaw 1987) and variations in surface roughness/shear between the pipe walls and the gas–liquid interface (Vollestad, Angheluta & Jensen 2020). Secondary currents are found to influence the primary mean velocity field as well as the distribution of Reynolds stresses (Ng et al.…”

Section: Introductionmentioning

confidence: 99%

Effect of secondary currents on the flow and turbulence in partially filled pipes

2022

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Large-eddy simulations of turbulent flow in partially filled pipes are conducted to investigate the effect of secondary currents on the friction factor, first- and second-order statistics and large-scale turbulent motion. The method is validated first and simulated profiles of the mean streamwise velocity, normal stresses and turbulent kinetic energy (TKE) are shown to be in good agreement with experimental data. The secondary flow is stronger in half- and three-quarters full pipes compared with quarter full or fully filled pipe flows, respectively. The origin of the secondary flow is examined by both the TKE budget and the steamwise vorticity equation, providing evidence that secondary currents originate from the corner between the free surface and the pipe walls, which is where turbulence production is larger than the sum of the remaining terms of the TKE budget. An extra source of streamwise vorticity production is found at the free surface near the centreline bisector, due to the two-component asymmetric turbulence there. The occurrence of dispersive stresses (due to secondary currents) reduces the contribution of the turbulent shear stress to the friction factor, which results in a reduction of the total friction factor of flows in half and three-quarters full pipes in comparison to a fully filled pipe flow. Furthermore, the presence of significant secondary currents inhibits very-large-scale motion (VLSM), which in turn reduces the strength and scales of near-wall streaks. Subsequently, near-wall coherent structures generated by streak instability and transient growth are significantly suppressed. The absence of VLSM and less coherent near-wall turbulence structures is supposedly responsible for the drag reduction in partially filled pipe flows relative to a fully filled pipe flow at an equivalent Reynolds number.

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Section: Introductionmentioning

confidence: 99%

Effect of secondary currents on the flow and turbulence in partially filled pipes

2022

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“…2012; Vollestad et al. 2020), which are the radial and azimuthal components of the divergence of the Reynolds stress tensor (i.e. in ).…”

Section: Resultsmentioning

confidence: 99%

“…2011), in circular pipes with a non-uniform roughness (Hinze 1973; Van't Westende et al. 2007) and stratified flows (Flores, Crowe & Griffith 1995; Vollestad, Angheluta & Jensen 2020). The particles transported within pipe flows can also induce a secondary flow.…”

Section: Introductionmentioning

confidence: 99%

The dominant mechanisms for each regime of secondary flows in horizontal particle-laden pipe flows

et al. 2022

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Numerical simulations have been conducted to identify the dominant mechanism responsible for driving secondary flow motions in horizontal particle-laden pipe flows, based on an analysis of the forces acting on each phase. A four-way coupling Euler–Lagrangian approach was employed, using direct numerical simulations for the gas phase and Lagrangian particle tracking to account for the drag, gravitational and lift forces, together with the interactions that occur for both particle–wall and inter-particle collisions. The four different flow regimes, which had been identified previously as depending on various combinations of flow parameters and are characterised by the secondary flow structures of both the fluid and particle phases, were identified via varying the mass loading alone from $\varPhi _m=0.4$ to $\varPhi _m=1.8$ . The distribution of the divergence of Reynolds stresses was used to help characterise the classes of the secondary fluid flow. This shows that secondary fluid flows of both the first and second kinds can either exist separately or co-exist in such flows. The forces exerted on the fluid phase by the pressure gradient and fluid–particle interactions were examined qualitatively and quantitatively to identify their contribution to the secondary fluid flow motions. A similar study was also applied to the drag, lift and gravitational forces exerted on the particle phase for the secondary particle flow motions. These were found to explain the secondary flows of both the fluid and particle phases with regard to both the flow direction and magnitude, together with the interaction between the two phases.

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“…This is directly applicable to separating particles by size using inertia [792]. These vortices also emerge naturally in straight channels when two stratified fluid layers such as air and water flow through them [793], which is associated with huge pressure losses in (food) industrial pipelines. On the flip side, Dean vortices may be used along with UV-C to inactivate microoganisms in fruit juices [794].…”

Section: B Secondary Flowsmentioning

confidence: 99%

Culinary fluid mechanics and other currents in food science

Mathijssen¹,

Lisicki²,

Prakash³

et al. 2022

Preprint

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Innovations in fluid mechanics have refined food since ancient history, while creativity in cooking inspires science in return. Here, we review how recent advances in hydrodynamics are changing food science, and we highlight how the surprising phenomena that arise in the kitchen lead to discoveries and technologies across the disciplines, including rheology, soft matter, biophysics and molecular gastronomy. This review is structured like a menu, where each course highlights different aspects of culinary fluid mechanics. Our main themes include multiphase flows, complex fluids, thermal convection, hydrodynamic instabilities, viscous flows, granular matter, porous media, percolation, chaotic advection, interfacial phenomena, and turbulence. For every topic, we first provide an introduction accessible to food professionals and scientists in neighbouring fields. We then assess the state-of-the-art knowledge, the open problems, and likely directions for future research. New gastronomic ideas grow rapidly as the scientific recipes keep improving too.

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Experimental study of secondary flows above rough and flat interfaces in horizontal gas-liquid pipe flow

Cited by 13 publications

References 31 publications

Effect of secondary currents on the flow and turbulence in partially filled pipes

Effect of secondary currents on the flow and turbulence in partially filled pipes

The dominant mechanisms for each regime of secondary flows in horizontal particle-laden pipe flows

Culinary fluid mechanics and other currents in food science

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