Turbulent bulk viscosity

Nucci, Carmine Di; Pasquali, Davide; Celli, Daniele; Pasculli, Antonio; Fischione, Piera; Risio, Marcello Di

doi:10.1016/j.euromechflu.2020.07.004

Cited by 9 publications

(11 citation statements)

References 10 publications

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“…Following [14], in the turbulent flow regime, the mean-flow equations which correspond to Equations ( 8)-( 10) can be written as follows:…”

Section: Dimensionless Mean-flow Field Equationsmentioning

confidence: 99%

“…is the Reynolds stress tensor. Equations ( 28)-(30) can be obtained using the Reynolds decomposition along with the Russo Spena Assumption (RSAss) [14] setting:…”

Section: Dimensionless Mean-flow Field Equationsmentioning

confidence: 99%

“…The deviatoric stress tensor (T Re ) dev is related to additional shear stresses; the isotropic part (T Re ) iso , which is related to additional relative normal stresses, can be expressed using the constitutive equation [14]:…”

Section: Dimensionless Mean-flow Field Equationsmentioning

confidence: 99%

“…Within the framework of CCT, ref. [14] have developed an idea suggested by [15][16][17], and they have proposed a 3D model for the unsteady isothermal flow of a simple isotropic linear viscous fluid in the liquid state (i.e., with low compressibility), which involves the turbulent bulk viscosity. In this paper, we re-examine this model.…”

Section: Introductionmentioning

confidence: 99%

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New Dimensionless Number for the Transition from Viscous to Turbulent Flow

Nucci

Celli

Pasquali

et al. 2022

Fluids

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Within the framework of Classical Continuum Thermomechanics, we consider an unsteady isothermal flow of a simple isotropic linear viscous fluid in the liquid state to investigate the transient flow conditions. Despite the attention paid to this problem by several research works, it seems that the understanding of turbulence in these flow conditions is controversial. We propose a dimensionless procedure that highlights some aspects related to the transition from viscous to turbulent flow which occurs when a finite amplitude pressure wave travels through the fluid. This kind of transition is demonstrated to be described by a (first) dimensionless number, which involves the bulk viscosity. Furthermore, in the turbulent flow regime, we show the role played by a (second) dimensionless number, which involves the turbulent bulk viscosity, in entropy production. Within the frame of the 1D model, we test the performance of the dimensionless procedure using experimental data on the pressure waves propagation in a long pipe (water hammer phenomenon). The obtained numerical results show good agreement with the experimental data. The results’ inspection confirms the predominant role of the turbulent bulk viscosity on energy dissipation processes.

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“…Following [14], in the turbulent flow regime, the mean-flow equations which correspond to Equations ( 8)-( 10) can be written as follows:…”

Section: Dimensionless Mean-flow Field Equationsmentioning

confidence: 99%

“…is the Reynolds stress tensor. Equations ( 28)-(30) can be obtained using the Reynolds decomposition along with the Russo Spena Assumption (RSAss) [14] setting:…”

Section: Dimensionless Mean-flow Field Equationsmentioning

confidence: 99%

Section: Dimensionless Mean-flow Field Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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New Dimensionless Number for the Transition from Viscous to Turbulent Flow

Nucci

Celli

Pasquali

et al. 2022

Fluids

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“…The most advanced approaches, based on the balance equations of physics are pursued by computational fluid dynamics (CFD). CFD relies on solving Navier-Stokes flow equations, including turbulence [2][3][4][5], the results of which are, consequently, very complex from a mathematical point of view. Therefore, to avoid at least the further complexity of the geometric domain discretization, the meshless approach has been proposed and adopted.…”

Section: Introductionmentioning

confidence: 99%

Surface Water Flow Balance of a River Basin Using a Shallow Water Approach and GPU Parallel Computing—Pescara River (Italy) as Test Case

Pasculli

Longo

Sciarra

et al. 2022

Water

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The analysis and prevention of hydrogeological risks plays a very important role and, currently, much attention is paid to advanced numerical models that correspond more to physical reality and whose aim is to reproduce complex environmental phenomena even for long times and on large spatial scales. Within this context, the feasibility of performing an effective balance of surface water flow relating to several months was explored, based on accurate hydraulic and mathematical-numerical models applied to a system at the scale of a hydrographic basin. To pursue this target, a 2D Riemann–Godunov shallow-water approach, solved in parallel on a graphical processing unit (GPU), able to drastically reduce calculation time, and implemented into the RiverFlow2D code (2017 version), was selected. Infiltration and evapotranspiration were included but in a simplified way, in order to face the calibration and validation simulations and because, despite the parallel approach, it is very demanding even for the computer time requirement. As a test case the Pescara river basin, located in Abruzzo, Central Italy, covering an area of 813 km2 and well representative of a typical medium-sized basin, was selected. The topography was described by a 10 × 10 m digital terrain model (DTM), covered by about 1,700,000 triangular elements, equipped with 11 rain gauges, distributed over the entire area, with some hydrometers and some fluviometric stations. Calibration, and validation were performed considering the flow data measured at a station located in close proximity to the mouth of the river. The comparison between the numerical and measured data, and also from a statistical point of view, was quite satisfactory. A further important outcome was the capability to highlight any differences between the numerical flow-rate balance carried out on the basis of the contributions of all known sources and the values actually measured. This characteristic of the applied modeling allows better calibration and verification not only of the effectiveness of much more simplified approaches, but also the entire network of measurement stations and could suggest the need for a more in-depth exploration of the territory in question. It would also enable the eventual identification of further hidden supplies of water inventory from underground sources and, accordingly, to enlarge the hydrographic and hydrogeological border of the basin under study. Moreover, the parallel computing platform would also allow the development of effective early warning systems, for example, of floods.

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Decomposition of the mechanical stress tensor: from the compressible Navier–Stokes equation to a turbulent potential flow model

Di Nucci,

Michele,

Di Risio

2024

Acta Mech

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We frame the mechanical stress tensor decomposition in a general procedure which involves the Helmholtz–Hodge decomposition. We highlight the impact of the mechanical stress tensor decomposition on the Navier–Stokes equation, with emphasis on the dissipation function. For fluids with low compressibility, we draw some insights on the Reynolds Averaged Navier–Stokes equations, and on the Reynolds stress tensor decomposition. We derive a turbulent potential flow model, and investigate the transition from viscous potential flow to turbulent potential flow. Under low Mach number approximation, we apply the turbulent potential flow model to one-dimensional propagation of large amplitude pressure waves in liquid-filled pipe.

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Turbulent bulk viscosity

Cited by 9 publications

References 10 publications

New Dimensionless Number for the Transition from Viscous to Turbulent Flow

New Dimensionless Number for the Transition from Viscous to Turbulent Flow

Surface Water Flow Balance of a River Basin Using a Shallow Water Approach and GPU Parallel Computing—Pescara River (Italy) as Test Case

Decomposition of the mechanical stress tensor: from the compressible Navier–Stokes equation to a turbulent potential flow model

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