## 2016 |
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11. | Picchi, Davide; Poesio, Pietro Uncertainty quantification of the two-fluid model and flow pattern transition boundaries predictions for the stratified flow regime by Montecarlo simulations and polynomial chaos expansions Conference 9th International Conference on Multiphase Flow, Florence, Italy, 22-27 May, 2016. @conference{Picchi_ICMF2016, title = {Uncertainty quantification of the two-fluid model and flow pattern transition boundaries predictions for the stratified flow regime by Montecarlo simulations and polynomial chaos expansions}, author = {Davide Picchi and Pietro Poesio}, year = {2016}, date = {2016-05-25}, address = {Florence, Italy, 22-27 May}, organization = {9th International Conference on Multiphase Flow,}, abstract = {The prediction of uncertainties is a growing interest in flow assurance industrial applications, but only few works have been presented on this topic. In this work, uncertainty quantification and a sensitivity analysis are performed on the steady and fully developed two-fluid model for the stratified flow regime. The effect of several variables on pressure drop and holdup predictions is investigated, such as fluid flow rates, geometry (the inclination angle and the pipe diameter), and fluid properties (density and viscosity); the case of a non-Newtonian power-law fluid behavior is presented. Flow pattern transition boundary predictions from the stratified flow regime obtained by the linear interfacial stability and the well-posedness analyses are also considered in the uncertainty analysis. Two approaches are used for this purpose: Monte Carlo simulations and the polynomial chaos expansions. The results obtained by the simulations are discussed and a sensitivity analysis is carried out on models predictions to understand the contribution of each input parameter.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } The prediction of uncertainties is a growing interest in flow assurance industrial applications, but only few works have been presented on this topic. In this work, uncertainty quantification and a sensitivity analysis are performed on the steady and fully developed two-fluid model for the stratified flow regime. The effect of several variables on pressure drop and holdup predictions is investigated, such as fluid flow rates, geometry (the inclination angle and the pipe diameter), and fluid properties (density and viscosity); the case of a non-Newtonian power-law fluid behavior is presented. Flow pattern transition boundary predictions from the stratified flow regime obtained by the linear interfacial stability and the well-posedness analyses are also considered in the uncertainty analysis. Two approaches are used for this purpose: Monte Carlo simulations and the polynomial chaos expansions. The results obtained by the simulations are discussed and a sensitivity analysis is carried out on models predictions to understand the contribution of each input parameter. | |

10. | Bonzanini, Arianna; Ferrari, Marco; Poesio, Pietro The effect of shear stress formulation and of the shape factor on slug capturing Conference 9th International Conference on Multiphase Flow, Florence, Italy, 22-27 May, 2016. @conference{Bonzanini_ICMF2016, title = {The effect of shear stress formulation and of the shape factor on slug capturing}, author = {Arianna Bonzanini and Marco Ferrari and Pietro Poesio}, year = {2016}, date = {2016-05-24}, address = {Florence, Italy, 22-27 May}, organization = {9th International Conference on Multiphase Flow,}, abstract = {In earlier works, we showed that a one-dimensional, hyperbolic, transient five equations two-fluid model is suitable to predict the formation, growth, and subsequent development of slugs in horizontal and near-horizontal flow. Statistical characteristics (slug velocity, length, and frequency) can be numerically predicted with results in good agreement with experimental and available data. As expected, in this model some approximated and simplified assumptions are adopted to close the problem. In our paper, we focus on two different aspects: the impact of the shear stress formulation on the results and the possibility to account for 2D effects by including the shape of the velocity profile by a proper shape factor. Shear stresses are modeled using the modified two-fluid model (MTF), which improves the standard closure relations starting from the ones based on the two-plate model. The results obtained using the standard model and the MFT are compared for different cases. Then, the effect on the numerical results of the shape factor, the parameter that takes into account the shape of the velocity profile, is investigated. The shape factor is computed at each time step and at each computational cell using the two plate approximation. The effect of shape factor is discussed with several examples.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } In earlier works, we showed that a one-dimensional, hyperbolic, transient five equations two-fluid model is suitable to predict the formation, growth, and subsequent development of slugs in horizontal and near-horizontal flow. Statistical characteristics (slug velocity, length, and frequency) can be numerically predicted with results in good agreement with experimental and available data. As expected, in this model some approximated and simplified assumptions are adopted to close the problem. In our paper, we focus on two different aspects: the impact of the shear stress formulation on the results and the possibility to account for 2D effects by including the shape of the velocity profile by a proper shape factor. Shear stresses are modeled using the modified two-fluid model (MTF), which improves the standard closure relations starting from the ones based on the two-plate model. The results obtained using the standard model and the MFT are compared for different cases. Then, the effect on the numerical results of the shape factor, the parameter that takes into account the shape of the velocity profile, is investigated. The shape factor is computed at each time step and at each computational cell using the two plate approximation. The effect of shape factor is discussed with several examples. | |

9. | Ferrari, Marco; Bonzanini, Arianna; Poesio, Pietro A slug capturing method applied to unconventional scenarios: high viscous oils and actual pipeline geometries Conference 9th International Conference on Multiphase Flow, Florence, Italy, 22-27 May, 2016. @conference{Ferrari_ICMF2016, title = {A slug capturing method applied to unconventional scenarios: high viscous oils and actual pipeline geometries}, author = {Marco Ferrari and Arianna Bonzanini and Pietro Poesio}, year = {2016}, date = {2016-05-23}, address = {Florence, Italy, 22-27 May}, organization = {9th International Conference on Multiphase Flow,}, abstract = {One-dimensional, hyperbolic, transient five equations two-fluid model can predict the formation, growth, and subsequent development of slugs in horizontal and near-horizontal flow automatically and they can even be used to predict the flow pattern, which is now a result and not an input parameter. Statistical characteristics (slug velocity, length, and frequency) are numerically predicted and they show good agreement with experimental data. However, the capabilities of this approach have been tested only for water-air flows in a straight horizontal pipe. In this paper, we move the focus on the application of the code to unconventional problems that involve high viscous oils and more complex pipe geometries. The paper is divided into two parts: in the first part of the paper, we test the possibility of slug capturing approach to describe and predict the relevant features of air/high viscosity oils. In that frame, we will check the effect of different closure relations on the results. Comparisons between slug velocity, frequency, and length distribution are discussed. In the second part of the paper, we move from simple geometries toward more complex conditions that may be representative of actual application cases. Despite only few experimental conditions being available, the comparison shows results in reasonable agreement.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } One-dimensional, hyperbolic, transient five equations two-fluid model can predict the formation, growth, and subsequent development of slugs in horizontal and near-horizontal flow automatically and they can even be used to predict the flow pattern, which is now a result and not an input parameter. Statistical characteristics (slug velocity, length, and frequency) are numerically predicted and they show good agreement with experimental data. However, the capabilities of this approach have been tested only for water-air flows in a straight horizontal pipe. In this paper, we move the focus on the application of the code to unconventional problems that involve high viscous oils and more complex pipe geometries. The paper is divided into two parts: in the first part of the paper, we test the possibility of slug capturing approach to describe and predict the relevant features of air/high viscosity oils. In that frame, we will check the effect of different closure relations on the results. Comparisons between slug velocity, frequency, and length distribution are discussed. In the second part of the paper, we move from simple geometries toward more complex conditions that may be representative of actual application cases. Despite only few experimental conditions being available, the comparison shows results in reasonable agreement. | |

8. | Losi, Gianluca; Poesio, Pietro An experimental investigation on the evolution of highly viscous oil slug lengths in horizontal pipes Conference 9th International Conference on Multiphase Flow, Florence, Italy, 22-27 May, 2016. @conference{Losi_ICMF2016, title = {An experimental investigation on the evolution of highly viscous oil slug lengths in horizontal pipes}, author = {Gianluca Losi and Pietro Poesio}, year = {2016}, date = {2016-05-23}, address = {Florence, Italy, 22-27 May}, organization = {9th International Conference on Multiphase Flow,}, abstract = {Slug flow is an unfair intermittent regime that often occurs in gas-liquid pipe flow and it is exhalted by the viscosity of the liquid phase. A relevant number of investigations have been carried out to quantify the average stable length of a liquid slug. However, in some practical application, be apart of more informations about slug length distributions and their evolution along the pipe is fundamental and, for this reason, slug length evolution for highly viscous oil/air slug flow is experimetally investigated. Six capacitance probes are placed along a 9 m – 22 mm I.D. pipe and they are used to monitor the slug flow structures evolution. An algorithm is developed to track and to measure slug velocities and lengths. A statistically relevant number of slugs is observed during the experiments and the probability density functions of their lengths are built. A literature slug tracking model has been implemented, which calculates the increase or decrease in length for each individual slug from a random inlet distribution, managing also events like shorter slugs disappearance. The PDFs, built from experiments, are compared with those calculated by the model and the results, both in terms of mean slug length and shapes of the distributions are quite good over a range of flow rates.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } Slug flow is an unfair intermittent regime that often occurs in gas-liquid pipe flow and it is exhalted by the viscosity of the liquid phase. A relevant number of investigations have been carried out to quantify the average stable length of a liquid slug. However, in some practical application, be apart of more informations about slug length distributions and their evolution along the pipe is fundamental and, for this reason, slug length evolution for highly viscous oil/air slug flow is experimetally investigated. Six capacitance probes are placed along a 9 m – 22 mm I.D. pipe and they are used to monitor the slug flow structures evolution. An algorithm is developed to track and to measure slug velocities and lengths. A statistically relevant number of slugs is observed during the experiments and the probability density functions of their lengths are built. A literature slug tracking model has been implemented, which calculates the increase or decrease in length for each individual slug from a random inlet distribution, managing also events like shorter slugs disappearance. The PDFs, built from experiments, are compared with those calculated by the model and the results, both in terms of mean slug length and shapes of the distributions are quite good over a range of flow rates. | |

## 2015 |
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7. | Arnone, Davide; Poesio, Pietro Experimental study on bi-phase flow air-oil in water emulsion Conference American Physical Society | Division of Fluid Dynamics, 68th Annual Meeting, Boston (Massachusetts), USA, 22–24 November, 2015. @conference{Arnone_APS2015, title = {Experimental study on bi-phase flow air-oil in water emulsion}, author = {Davide Arnone and Pietro Poesio}, year = {2015}, date = {2015-11-24}, address = {Boston (Massachusetts), USA, 22–24 November}, organization = {American Physical Society | Division of Fluid Dynamics, 68th Annual Meeting,}, abstract = {Bi-phase slug flow oil-in-water emulsion [5%-20%] and air through a horizontal pipe (inner diameter 22mm) is experimentally studied. A test with water and air has been performed as comparison. First we create and analyze the flow pattern map to identify slug flow liquid and air inlet conditions. Flow maps are similar for all the used liquid. A video analysis procedure using an high speed camera has been created to obtain all the characteristics of unit slugs: slug velocity, slug length, bubble velocity, bubbles length and slug frequency. We compare translational velocity and frequency with models finding a good agreement. We calculate the pdfs of the lengths to find the correlations between mean values and STD on different air and liquid superficial velocities. We also perform pressure measurements along the pipe. We conclude that the percentage of oil-in- water has no influence on results in terms of velocity, lengths, frequency and pressure drop. }, keywords = {}, pubstate = {published}, tppubtype = {conference} } Bi-phase slug flow oil-in-water emulsion [5%-20%] and air through a horizontal pipe (inner diameter 22mm) is experimentally studied. A test with water and air has been performed as comparison. First we create and analyze the flow pattern map to identify slug flow liquid and air inlet conditions. Flow maps are similar for all the used liquid. A video analysis procedure using an high speed camera has been created to obtain all the characteristics of unit slugs: slug velocity, slug length, bubble velocity, bubbles length and slug frequency. We compare translational velocity and frequency with models finding a good agreement. We calculate the pdfs of the lengths to find the correlations between mean values and STD on different air and liquid superficial velocities. We also perform pressure measurements along the pipe. We conclude that the percentage of oil-in- water has no influence on results in terms of velocity, lengths, frequency and pressure drop. | |

6. | Ferrari, Marco; Bonzanini, Arianna; Poesio, Pietro 5ESCARGOTS: a numerical code for slug capturing in pipes Conference 7th European-Japanese Two-Phase Flow Group Meeting, Zermatt, Switzerland, 11-15 October, 2015. @conference{Ferrari_Bonzanini_Zermatt, title = {5ESCARGOTS: a numerical code for slug capturing in pipes}, author = {Marco Ferrari and Arianna Bonzanini and Pietro Poesio}, year = {2015}, date = {2015-10-15}, address = {Zermatt, Switzerland, 11-15 October}, organization = {7th European-Japanese Two-Phase Flow Group Meeting,}, abstract = {This paper presents a novel numerical scheme for slug capturing in pipes using a 1D transient, hyperbolic, five equations two-fluid model. Previous work has shown that one-dimensional two-fluid models are able to capture slug flow automatically. In this work a similar approach is further developed using a new numerical scheme. Starting from a finite volume discretization of a five equations two-fluid model and adding appropriate closure relations, a slug capturing second order code (5ESCARGOTS code) is implemented and applied to air-water flows in horizontal pipes using a wide set of initial and boundary conditions. Slug velocity, length and frequency distributions are obtained from the simulation and compared to experimental and analytical results present in the literature, showing a fairly good agreement. The code is also used to detect the transition from stratified to slug flow patterns and results compare well with well-known results by previous researchers.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } This paper presents a novel numerical scheme for slug capturing in pipes using a 1D transient, hyperbolic, five equations two-fluid model. Previous work has shown that one-dimensional two-fluid models are able to capture slug flow automatically. In this work a similar approach is further developed using a new numerical scheme. Starting from a finite volume discretization of a five equations two-fluid model and adding appropriate closure relations, a slug capturing second order code (5ESCARGOTS code) is implemented and applied to air-water flows in horizontal pipes using a wide set of initial and boundary conditions. Slug velocity, length and frequency distributions are obtained from the simulation and compared to experimental and analytical results present in the literature, showing a fairly good agreement. The code is also used to detect the transition from stratified to slug flow patterns and results compare well with well-known results by previous researchers. | |

5. | Losi, Gianluca; Poesio, Pietro An experimental study on the drift velocity of gas bubble in highly viscous liquids Conference 26th International Symposium on Transport Phenomena, Leoben, Austria, 2015. @conference{Losi_ISTP26, title = {An experimental study on the drift velocity of gas bubble in highly viscous liquids}, author = {Gianluca Losi and Pietro Poesio}, year = {2015}, date = {2015-10-01}, address = {Leoben, Austria}, organization = {26th International Symposium on Transport Phenomena,}, abstract = {The motion of long bubbles in horizontal and slightly inclined pipes is a thoroughly investigated phenomenon since it is intimately related to oil and gas transportation and production problems (e.g oil transportation in pipelines or extraction). However, few results are available in literature for the drift velocity of a gas bubble in viscous liquids, although real industrial challenges deal with this type of fluids (e.g. heavy crude oil). The aim of this study is to experimentally analyze the effect of viscosity on the drift velocity of an air bubble in horizontal and inclined pipes. Two different measurement techniques are used: five capacitance probes are placed along the pipe to monitor the velocity evolution and image analysis is used to measure the bubble front velocity at two different distances from the outlet. The results of the measurements show that for horizontal case, differently with respect to Benjamin's theory (Benjamin (1968)), the bubble drift velocity is not constant while the front displaces along the pipe and, in general, the viscosity slows down the propagation rate of the bubble.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } The motion of long bubbles in horizontal and slightly inclined pipes is a thoroughly investigated phenomenon since it is intimately related to oil and gas transportation and production problems (e.g oil transportation in pipelines or extraction). However, few results are available in literature for the drift velocity of a gas bubble in viscous liquids, although real industrial challenges deal with this type of fluids (e.g. heavy crude oil). The aim of this study is to experimentally analyze the effect of viscosity on the drift velocity of an air bubble in horizontal and inclined pipes. Two different measurement techniques are used: five capacitance probes are placed along the pipe to monitor the velocity evolution and image analysis is used to measure the bubble front velocity at two different distances from the outlet. The results of the measurements show that for horizontal case, differently with respect to Benjamin's theory (Benjamin (1968)), the bubble drift velocity is not constant while the front displaces along the pipe and, in general, the viscosity slows down the propagation rate of the bubble. | |

4. | Gordiychuk, Andriy; Poesio, Pietro Experimental investigation on the effect of operating conditions on the Sauter mean diameter of microbubbles for a Venturi type bubble generator Conference 26th International Symposium on Transport Phenomena, Leoben, Austria, 2015. @conference{Gordiychuk_ISTP26, title = {Experimental investigation on the effect of operating conditions on the Sauter mean diameter of microbubbles for a Venturi type bubble generator}, author = {Andriy Gordiychuk and Pietro Poesio}, year = {2015}, date = {2015-10-01}, address = {Leoben, Austria}, organization = {26th International Symposium on Transport Phenomena,}, keywords = {}, pubstate = {published}, tppubtype = {conference} } | |

3. | Beretta, Gian Paolo; Janbozorgi, Mohammad; Metghalchi, Hameed Use of degree of disequilibrium analysis to select kinetic constraints for the Rate-Controlled Constrained-Equilibrium (RCCE) method Conference ECOS 2015 - The 28th International Conference On Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, Pau, France, 2015. @conference{Beretta_ECOS2015, title = {Use of degree of disequilibrium analysis to select kinetic constraints for the Rate-Controlled Constrained-Equilibrium (RCCE) method}, author = {Gian Paolo Beretta and Mohammad Janbozorgi and Hameed Metghalchi}, year = {2015}, date = {2015-07-03}, address = {Pau, France}, organization = {ECOS 2015 - The 28th International Conference On Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems,}, abstract = {The Rate-Controlled Constrained-Equilibrium (RCCE) method provides a general framework that enables, with the same ease, reduced order kinetic modelling at three different levels of approximation: shifting equilibrium, frozen equilibrium, as well as non-equilibrium chemical kinetics. The method in general requires a significantly smaller number of differential equations than the dimension of the underlying Detailed Kinetic Model (DKM) for acceptable accuracies. To provide accurate approximations, however, the method requires accurate identification of the bottleneck kinetic mechanisms responsible for slowing down the relaxation of the state of the system towards local chemical equilibrium. In other words, the method requires that such bottleneck mechanisms be characterized by means of a set of representative constraints. So far, a drawback of the RCCE method has been the absence of a systematic algorithm that would allow a fully automatable identification of the best constraints for a given range of thermodynamic conditions and a required level of approximation. In this paper, we provide the first of two steps towards such algorithm based on the analysis of the degrees of disequilibrium (DoD) of chemical reactions in the underlying DKM. In any given DKM the number of rate-limiting kinetic bottlenecks is generally much smaller than the number of species in the model. As a result, the DoDs of all the chemical reactions effectively assemble into a small number of groups that bear the information of the rate-controlling constraints. The DoDs of all reactions in each group exhibit almost identical behaviour (time evolution, spatial dependence). Upon identification of these groups, the proposed kernel analysis of N matrices that are obtained from the stoichiometric coefficients yields the N constraints that effectively control the dynamics of the system. The method is demonstrated within the framework of modeling the expansion of products of the oxy-combustion of hydrogen through a quasi onedimensional supersonic nozzle. The analysis predicts and RCCE simulations confirm that, under the geometrical and boundary conditions considered, the underlying DKM is accurately represented by only two bottleneck kinetic mechanisms, instead of the three constraints identified for the same problem in a recently published work also based, in part, on DoD analysis. }, keywords = {}, pubstate = {published}, tppubtype = {conference} } The Rate-Controlled Constrained-Equilibrium (RCCE) method provides a general framework that enables, with the same ease, reduced order kinetic modelling at three different levels of approximation: shifting equilibrium, frozen equilibrium, as well as non-equilibrium chemical kinetics. The method in general requires a significantly smaller number of differential equations than the dimension of the underlying Detailed Kinetic Model (DKM) for acceptable accuracies. To provide accurate approximations, however, the method requires accurate identification of the bottleneck kinetic mechanisms responsible for slowing down the relaxation of the state of the system towards local chemical equilibrium. In other words, the method requires that such bottleneck mechanisms be characterized by means of a set of representative constraints. So far, a drawback of the RCCE method has been the absence of a systematic algorithm that would allow a fully automatable identification of the best constraints for a given range of thermodynamic conditions and a required level of approximation. In this paper, we provide the first of two steps towards such algorithm based on the analysis of the degrees of disequilibrium (DoD) of chemical reactions in the underlying DKM. In any given DKM the number of rate-limiting kinetic bottlenecks is generally much smaller than the number of species in the model. As a result, the DoDs of all the chemical reactions effectively assemble into a small number of groups that bear the information of the rate-controlling constraints. The DoDs of all reactions in each group exhibit almost identical behaviour (time evolution, spatial dependence). Upon identification of these groups, the proposed kernel analysis of N matrices that are obtained from the stoichiometric coefficients yields the N constraints that effectively control the dynamics of the system. The method is demonstrated within the framework of modeling the expansion of products of the oxy-combustion of hydrogen through a quasi onedimensional supersonic nozzle. The analysis predicts and RCCE simulations confirm that, under the geometrical and boundary conditions considered, the underlying DKM is accurately represented by only two bottleneck kinetic mechanisms, instead of the three constraints identified for the same problem in a recently published work also based, in part, on DoD analysis. | |

## 2014 |
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2. | Beretta, Gian Paolo Steepest entropy ascent model for far-non-equilibrium thermodynamics. Unified implementation of the maximum entropy production principle Conference 1st International Electronic Conference on Entropy and Its Applications, internet environment, 2014. @conference{Beretta_ECEA1_2014, title = {Steepest entropy ascent model for far-non-equilibrium thermodynamics. Unified implementation of the maximum entropy production principle}, author = {Gian Paolo Beretta}, year = {2014}, date = {2014-11-21}, address = {internet environment}, organization = {1st International Electronic Conference on Entropy and Its Applications,}, abstract = {We report on work published recently in Phys. Rev. E 90, 042113 (2014), where by suitable reformulations, we cast the mathematical frameworks of several well-known different approaches to the description of non-equilibrium dynamics into a unified formulation valid in all these contexts, which extends to such frameworks the concept of Steepest Entropy Ascent (SEA) dynamics introduced by the present author in previous works on quantum thermodynamics. Actually, the present formulation constitutes a generalization also for the quantum thermodynamics framework. The analysis emphasizes that in the SEA modeling principle a key role is played by the geometrical metric with respect to which to measure the length of a trajectory in state space. In the near thermodynamic equilibrium limit, the metric tensor turns is directly related to the Onsager’s generalized resistivity tensor. Therefore, through the identification of a suitable metric field which generalizes the Onsager generalized resistance to the arbitrarily far non-equilibrium domain, most of the existing theories of non-equilibrium thermodynamics can be cast in such a way that the state exhibits the spontaneous tendency to evolve in state space along the path of SEA compatible with the conservation constraints and the boundary conditions. The resulting unified family of SEA dynamical models are all intrinsically and strongly consistent with the second law of thermodynamics. The nonnegativity of the entropy production is a general and readily proved feature of SEA dynamics. In several of the different approaches to non-equilibrium description we consider here, the SEA concept has not been investigated before. We believe it defines the precise meaning and the domain of general validity of the so-called Maximum Entropy Production principle. Therefore, it is hoped that the present unifying approach may prove useful in providing a fresh basis for effective, thermodynamically consistent, numerical models and theoretical treatments of irreversible conservative relaxation towards equilibrium from far non-equilibrium states. The mathematical frameworks are: A) Statistical or Information Theoretic Models of Relaxation; B) Small-Scale and Rarefied Gases Dynamics (i.e., kinetic models for the Boltzmann equation); C) Rational Extended Thermodynamics, Macroscopic Non-Equilibrium Thermodynamics, and Chemical Kinetics; D) Mesoscopic Non-Equilibrium Thermodynamics, Continuum Mechanics with Fluctuations; E) Quantum Statistical Mechanics, Quantum Thermodynamics, Mesoscopic Non-Equilibrium Quantum Thermodynamics, and Intrinsic Quantum Thermodynamics.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } We report on work published recently in Phys. Rev. E 90, 042113 (2014), where by suitable reformulations, we cast the mathematical frameworks of several well-known different approaches to the description of non-equilibrium dynamics into a unified formulation valid in all these contexts, which extends to such frameworks the concept of Steepest Entropy Ascent (SEA) dynamics introduced by the present author in previous works on quantum thermodynamics. Actually, the present formulation constitutes a generalization also for the quantum thermodynamics framework. The analysis emphasizes that in the SEA modeling principle a key role is played by the geometrical metric with respect to which to measure the length of a trajectory in state space. In the near thermodynamic equilibrium limit, the metric tensor turns is directly related to the Onsager’s generalized resistivity tensor. Therefore, through the identification of a suitable metric field which generalizes the Onsager generalized resistance to the arbitrarily far non-equilibrium domain, most of the existing theories of non-equilibrium thermodynamics can be cast in such a way that the state exhibits the spontaneous tendency to evolve in state space along the path of SEA compatible with the conservation constraints and the boundary conditions. The resulting unified family of SEA dynamical models are all intrinsically and strongly consistent with the second law of thermodynamics. The nonnegativity of the entropy production is a general and readily proved feature of SEA dynamics. In several of the different approaches to non-equilibrium description we consider here, the SEA concept has not been investigated before. We believe it defines the precise meaning and the domain of general validity of the so-called Maximum Entropy Production principle. Therefore, it is hoped that the present unifying approach may prove useful in providing a fresh basis for effective, thermodynamically consistent, numerical models and theoretical treatments of irreversible conservative relaxation towards equilibrium from far non-equilibrium states. The mathematical frameworks are: A) Statistical or Information Theoretic Models of Relaxation; B) Small-Scale and Rarefied Gases Dynamics (i.e., kinetic models for the Boltzmann equation); C) Rational Extended Thermodynamics, Macroscopic Non-Equilibrium Thermodynamics, and Chemical Kinetics; D) Mesoscopic Non-Equilibrium Thermodynamics, Continuum Mechanics with Fluctuations; E) Quantum Statistical Mechanics, Quantum Thermodynamics, Mesoscopic Non-Equilibrium Quantum Thermodynamics, and Intrinsic Quantum Thermodynamics. | |

1. | Picchi, Davide; Manerba, Yuri; Correra, Sebastiano; Margarone, Michele; Poesio, Pietro Experimental investigation of gas/non-Newtonian liquid two-phase ﬂows through horizontal and slightly inclined pipes Conference 13th International Conference Multiphase Flow in Industrial Plants, Sestri Levante (Genova), Italy, 2014. @conference{Picchi_MFIP2014, title = {Experimental investigation of gas/non-Newtonian liquid two-phase ﬂows through horizontal and slightly inclined pipes}, author = {Davide Picchi and Yuri Manerba and Sebastiano Correra and Michele Margarone and Pietro Poesio}, year = {2014}, date = {2014-09-19}, address = {Sestri Levante (Genova), Italy}, organization = {13th International Conference Multiphase Flow in Industrial Plants,}, abstract = {In chemical and oil industry gas/non-Newtonian liquid two-phase flows are frequently encountered. In this work we investigate experimentally the flow characteristics of air/non-Newtonian shear thinning liquid systems in horizontal and slightly inclined smooth pipes. The experiments are performed in a 9-m-long glass pipe using air and three different CMC solutions as test fluids. Flow pattern maps are built by visual observation and the different flow conditions are recorded by a high-speed camera. The observed flow patterns are stratified, plug, and slug flow. The effects of the pipe inclination and the fluid properties in terms of flow pattern maps are presented. Transition boundaries predictions from the stratified flow regime are compared with the experimental observation showing a good agreement. Pressure gradients are measured and the drag reduction by the injection of a gas in a shear thinning fluid flow is studied. In particular we focus our attention to the study of the slug flow regime: a model taken from the literature is extended and the pressure drops predictions are compared to the experimental data showing an acceptable accordance. }, keywords = {}, pubstate = {published}, tppubtype = {conference} } In chemical and oil industry gas/non-Newtonian liquid two-phase flows are frequently encountered. In this work we investigate experimentally the flow characteristics of air/non-Newtonian shear thinning liquid systems in horizontal and slightly inclined smooth pipes. The experiments are performed in a 9-m-long glass pipe using air and three different CMC solutions as test fluids. Flow pattern maps are built by visual observation and the different flow conditions are recorded by a high-speed camera. The observed flow patterns are stratified, plug, and slug flow. The effects of the pipe inclination and the fluid properties in terms of flow pattern maps are presented. Transition boundaries predictions from the stratified flow regime are compared with the experimental observation showing a good agreement. Pressure gradients are measured and the drag reduction by the injection of a gas in a shear thinning fluid flow is studied. In particular we focus our attention to the study of the slug flow regime: a model taken from the literature is extended and the pressure drops predictions are compared to the experimental data showing an acceptable accordance. |