Extension of the 1D Unsteady Friction Model for Rapidly Accelerating and Decelerating Turbulent Pipe Flows

Guerrero, Byron; Lambert, Martin F.; Chin, Rey

doi:10.1061/(asce)hy.1943-7900.0001998

Cited by 4 publications

(8 citation statements)

References 37 publications

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“…In other words, the nearly frozen behaviour of the pressure strain term during stage I, which redistributes turbulence energy in the three orthogonal directions, induces anisotropy in the response of the three normal components of the Reynolds stress tensor. As a result, this observation provides a feasible explanation of the different delays and anisotropies observed in the response of the different turbulence components in both accelerating (He & Jackson 2000) and decelerating flows (Seddighi et al 2011;Guerrero et al 2022).…”

Section: Time Dependence Of the U Z U Z Budgetsmentioning

confidence: 63%

“…The first term on the right-hand side of (6.1) (C δ f ) is equal to the Fanning friction factor and, thus, it quantifies the laminar contribution to the flow. As explained in Guerrero et al (2022), C δ f becomes negligible at high Reynolds numbers. The second term (C T f ) on the right-hand side of (6.1) represents the turbulent contributions.…”

Section: Dynamic Contributions Into the Skin Friction Coefficientmentioning

confidence: 75%

“…During the last ten years, special attention has been paid to the time response of the frictional drag in accelerating turbulent pipe and channel flows (He, Ariyaratne & Vardy 2011). In that regard, several numerical studies have been performed (He & Seddighi 2013He, Seddighi & He 2016;Jung & Kim 2017;Mathur et al 2018). The detailed study conducted by He & Seddighi (2013) analysed the temporal dependence of the mean skin friction coefficient C f together with other mean flow statistics to determine the stages undergone by a turbulent channel flow following a step-up increase in the flow rate, using DNS data sets.…”

Section: Accelerating Turbulent Flowmentioning

confidence: 99%

“…This implies that, on average, a small layer of negative azimuthal vorticity is produced at the wall during the flow excursion. Indeed, in the recent work by Guerrero et al (2022) it was shown that large-scale patches of negative wall shear stress are generated during the early flow excursion in a decelerating flow. It should also be mentioned that vorticity can only be produced at the wall (Batchelor 1967;Morton 1984) due to local accelerations.…”

Section: Time Response Of the Flow Scalesmentioning

confidence: 99%

“…until the flow fully develops to its final steady conditions). Indeed, to the knowledge of the present authors, there only exist very few DNS studies that have attempted to examine the transient frictional drag in decelerating internal flows (Chung 2005; Mathur 2016; Guerrero, Lambert & Chin 2022), and in all those cases, the studies were conducted at low turbulence.…”

Section: Introductionmentioning

confidence: 99%

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Transient behaviour of decelerating turbulent pipe flows

2023

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This investigation characterises the time response and the transient turbulence dynamics undergone by rapidly decelerating turbulent pipe flows. A series of direct numerical simulations of decelerating flows between two steady Reynolds numbers were conducted for this purpose. The statistical analyses reveal that rapidly decelerating turbulent flows undergo four coherent, unambiguous transitional stages: inertial (stage I), a dramatic change of sign in the viscous force associated with the decay of the viscous shear stress at the wall together with a mild turbulence decay in the viscous sublayer; friction recovery (stage II), a recovery in viscous force and progressive decay in the turbulent inertia at the near-wall region; turbulence decay (stage III), a balanced decay in both turbulent inertia and viscous force at the near-wall and overlap regions; core relaxation (stage IV), slow turbulence decay at the core region. The FIK identity derived by Fukagata, Iwamoto and Kasagi (Phys. Fluids, vol. 14, 2002, L73–L76) was used to understand further how the flow dynamics influence the time response of the skin friction coefficient ( $C_f$ ). The results show that although $C_f$ plateaus during the fourth stage, the turbulent contribution keeps decaying, undershoots and finally recovers to attain its final steady value. The time evolution of the azimuthal vorticity ( $\omega _\theta$ ) flux reveals that as the flow is decelerated, a layer of negative $\omega _\theta$ is produced at the wall during the flow excursion. As time progresses, this negative vorticity propagates in the wall-normal direction, attenuating the pre-existing vorticity and producing a decay in the turbulence levels.

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Section: Time Dependence Of the U Z U Z Budgetsmentioning

confidence: 63%

Section: Dynamic Contributions Into the Skin Friction Coefficientmentioning

confidence: 75%