On the effects of the free-stream turbulence on the heat transfer from a sphere

Rodríguez, I.; Lehmkuhl, O.; Sòria, M.

doi:10.1016/j.ijheatmasstransfer.2020.120579

Cited by 12 publications

(7 citation statements)

References 47 publications

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“…In their simulations of flow past a sphere at , Rodriguez et al. (2021) found that in the subcritical regime, increase in leads to shrinking of the recirculation zone behind the sphere. The increase in the drag coefficient observed here can be explained by the shrinking of the recirculation zone.…”

Section: Resultsmentioning

confidence: 99%

“…In presence of FST, suppression of vortex shedding in the wake of the sphere at subcritical was observed experimentally by Tyagi et al. (2006) and computationally by Rodriguez, Lehmkuhl & Soria (2021). Raithby & Eckert (1968) found that not only the drag crisis take place at a lower , but it also becomes gradual with increasing FST.…”

Section: Introductionmentioning

confidence: 85%

“…The most prominent effect of FST is reduction in the critical Re for the onset of the drag crisis (Raithby & Eckert 1968;Moradian, Ting & Cheng 2009;Son et al 2010;Desai, Shakya & Mittal 2021). In presence of FST, suppression of vortex shedding in the wake of the sphere at subcritical Re was observed experimentally by Tyagi et al (2006) and computationally by Rodriguez, Lehmkuhl & Soria (2021). Raithby & Eckert (1968) found that not only the drag crisis take place at a lower Re, but it also becomes gradual with increasing FST.…”

Section: Introductionmentioning

confidence: 94%

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Effect of free stream turbulence on the topology of laminar separation bubble on a sphere

Desai

Mittal

2022

J. Fluid Mech.

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The topology of a laminar separation bubble (LSB) on a sphere in the critical regime is investigated via experiments at five turbulent intensities: $T_u=0.06\,\%$ , $0.42\,\%$ , $0.71\,\%$ , $1.00\,\%$ and $1.36\,\%$ . The drag crisis occurs at a lower $Re$ and becomes gradual with increasing $T_u$ . The flow is devoid of the LSB at the onset of the critical regime. It forms on a small part of the sphere and not at all azimuthal locations, early in the critical regime. The LSB forms at more azimuthal locations with increasing $Re$ . This azimuthal expansion of the LSB is accompanied by intermittency for a small range of $Re$ . Towards the end of the critical regime, an axisymmetric LSB forms on the sphere at all time instants. A model is proposed to estimate the azimuthal extent and distribution of the LSB from the mean force coefficients of a flow state. The model predicts that the LSB forms as multiple segments for a large part of the critical regime. During the spatial growth of the LSB with $Re$ in the critical regime, some of its fragments relocate to alternate locations. Moderate increase in $T_u$ ( $0.42\,\% \leq T_u \leq 0.71\,\%$ ) leads to rich dynamics with several intermittent flow states. However, fewer intermittent states are observed beyond a certain $T_u$ ( ${\geq }1.00\,\%$ ).

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 94%

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Effect of free stream turbulence on the topology of laminar separation bubble on a sphere

Desai

Mittal

2022

J. Fluid Mech.

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“…The pressure-velocity coupling is solved, using a non-incremental fractional-step method, whereas equations are explicitly integrated in time using a fourthorder Runge-Kutta method [23] combined with an eigenvalue-based time-step estimator [24]. The methodology used proved to be suitable on the resolution of turbulent flows (see, for instance, the author's recent works [25][26][27][28]) .…”

Section: Methodsmentioning

confidence: 99%

On the Characteristics of the Super-Critical Wake behind a Circular Cylinder

Rodríguez

Lehmkuhl

2021

Fluids

Self Cite

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The flow topology of the wake behind a circular cylinder at the super-critical Reynolds number of Re=7.2×105 is investigated by means of large eddy simulations. In spite of the many research works on circular cylinders, there are no studies concerning the main characteristics and topology of the near wake in the super-critical regime. Thus, the present work attempts to fill the gap in the literature and contribute to the analysis of both the unsteady wake and the turbulent statistics of the flow. It is found that although the wake is symmetric and preserves similar traits to those observed in the sub-critical regime, such as the typical two-lobed configuration in the vortex formation zone, important differences are also observed. Owing to the delayed separation of the flow and the transition to turbulence in the attached boundary layer, Reynolds stresses peak in the detached shear layers close to the separation point. The unsteady mean flow is also investigated, and topological critical points are identified in the vortex formation zone and the near wake. Finally, time-frequency analysis is performed by means of wavelets. The study shows that in addition to the vortex shedding frequency, the inception of instabilities that trigger transition to turbulence occurs intermittently in the attached boundary layer and is registered as a phenomenon of variable intensity in time.

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“…They have shown that the vanishing skin friction is delayed by enhancing the mixed convection in both steady and unsteady fluid flow cases. Rodriguez et al, [5] investigated free-stream turbulence natural convective heat transfer flow from the sphere. It was found that the drag coefficient and the Nusselt number are increased with turbulence interruption and momentum transfer is also increased from the surrounding fluid and energizes the separated shear layer.…”

Section: Introductionmentioning

confidence: 99%

Using Micropolar Nanofluid under a Magnetic Field to Enhance Natural Convective Heat Transfer around a Spherical Body

Yaseen¹,

Alwawi

Swalmeh³

et al. 2022

ARFMTS

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An analysis is discussed of the heat and mass transfer for micropolar nanofluid in presence of natural convection from a spherical body with magneto-hydrodynamic (MHD) effects. The constant wall temperature boundary condition is also studied. By employing proper similarity transformations, the governing equations are converted into a set of partial differential equations (PDEs) with the used boundary conditions, which can then be solved numerically via the efficient Keller-box implicit numerical finite difference method. The numerical results of impacts of the controlling parameters on heat transfer physical quantities have been presented, tabular and graphically, by MATLAB symbolic software. Comparisons of the current study results to previously published results show good agreement, indicating that our numerical computations are legitimate and accurate. Increasing nanoparticle volume fraction is observed to depress local skin friction, Nusselt number, and angular velocity while the reverse effects are observed for velocity and temperature.

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On the effects of the free-stream turbulence on the heat transfer from a sphere

Cited by 12 publications

References 47 publications

Effect of free stream turbulence on the topology of laminar separation bubble on a sphere

Effect of free stream turbulence on the topology of laminar separation bubble on a sphere

On the Characteristics of the Super-Critical Wake behind a Circular Cylinder

Using Micropolar Nanofluid under a Magnetic Field to Enhance Natural Convective Heat Transfer around a Spherical Body

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