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The correct prediction of heat transfer in turbulent flows is relevant in almost all industrial applications but many of the heat transfer models available in literature are validated only for ordinary fluids with Pr ≃ 1. In commercial Computational Fluid Dynamics codes only turbulence models with a constant turbulent Prandtl number of 0.85 — 0.9 are usually implemented but in heavy liquid metals with low Prandtl numbers it is well known that these models fail to reproduce correlations based on experimental data. In these fluids heat transfer is mainly due to molecular diffusion and the time scales of temperature and velocity fields are rather different, so simple turbulence models based on similarity between temperature and velocity cannot reproduce experimental correlations. In order to reproduce experimental results and Direct Numerical Simulation data obtained for fluids with Pr ≃ 0.025 we introduce a κ-ε-κ θ -ε θ turbulence model. This model, however, shows some numerical instabilities mainly due to the strong coupling between κ and ε on the walls. In order to fix this problem we reformulate the model into a new four parameter κ-ω-κ θ -ω θ where the dissipation rate on the wall is completely independent on the fluctuations. The model improves numerical stability and convergence. Numerical simulations in plane and channel geometries are reported and compared with experimental, Direct Numerical Simulation results and with results obtained with the κ-ε formulation, in order to show the model capabilities and validate the improved κ-ω model.

In this work we investigate the potentialities of multi-scale engineering techniques to approach complex problems related to biomedical and biological fields. In particular we study the interaction between blood and blood vessel focusing on the presence of an aneurysm. The study of each component of the cardiovascular system is very difficult due to the fact that the movement of the fluid and solid is determined by the rest of system through dynamical boundary conditions. The use of multi-scale techniques allows us to investigate the effect of the whole loop on the aneurysm dynamic. A three-dimensional fluid-structure interaction model for the aneurysm is developed and coupled to a mono-dimensional one for the remaining part of the cardiovascular system, where a point zero-dimensional model for the heart is provided. In this manner it is possible to achieve rigorous and quantitative investigations of the cardiovascular disease without loosing the system dynamic. In order to study this biomedical problem we use a monolithic fluid-structure interaction (FSI) model where the fluid and solid equations are solved together. The use of a monolithic solver allows us to handle the convergence issues caused by large deformations. By using this monolithic approach different solid and fluid regions are treated as a single continuum and the interface conditions are automatically taken into account. In this way the iterative process characteristic of the commonly used segregated approach, it is not needed any more.

In this work we investigate the potentialities of multi-scale engineering techniques to approach complex problems related to biomedical and biological fields. In particular we study the interaction between blood and blood vessel focusing on the presence of an aneurysm. The study of each component of the cardiovascular system is very difficult due to the fact that the movement of the fluid and solid is determined by the rest of system through dynamical boundary conditions. The use of multi-scale techniques allows us to investigate the effect of the whole loop on the aneurysm dynamic. A three-dimensional fluid-structure interaction model for the aneurysm is developed and coupled to a mono-dimensional one for the remaining part of the cardiovascular system, where a point zero-dimensional model for the heart is provided. In this manner it is possible to achieve rigorous and quantitative investigations of the cardiovascular disease without loosing the system dynamic. In order to study this biomedical problem we use a monolithic fluid-structure interaction (FSI) model where the fluid and solid equations are solved together. The use of a monolithic solver allows us to handle the convergence issues caused by large deformations. By using this monolithic approach different solid and fluid regions are treated as a single continuum and the interface conditions are automatically taken into account. In this way the iterative process characteristic of the commonly used segregated approach, it is not needed any more.

In this work we investigate the potentialities of multi-scale engineering techniques to approach complex problems related to biomedical and biological fields. In particular we study the interaction between blood and blood vessel focusing on the presence of an aneurysm. The study of each component of the cardiovascular system is very difficult due to the fact that the movement of the fluid and solid is determined by the rest of system through dynamical boundary conditions. The use of multi-scale techniques allows us to investigate the effect of the whole loop on the aneurysm dynamic. A three-dimensional fluid-structure interaction model for the aneurysm is developed and coupled to a mono-dimensional one for the remaining part of the cardiovascular system, where a point zero-dimensional model for the heart is provided. In this manner it is possible to achieve rigorous and quantitative investigations of the cardiovascular disease without loosing the system dynamic. In order to study this biomedical problem we use a monolithic fluid-structure interaction (FSI) model where the fluid and solid equations are solved together. The use of a monolithic solver allows us to handle the convergence issues caused by large deformations. By using this monolithic approach different solid and fluid regions are treated as a single continuum and the interface conditions are automatically taken into account. In this way the iterative process characteristic of the commonly used segregated approach, it is not needed any more.

In this work we investigate the potentialities of multi-scale engineering techniques to approach complex problems related to biomedical and biological fields. In particular we study the interaction between blood and blood vessel focusing on the presence of an aneurysm. The study of each component of the cardiovascular system is very difficult due to the fact that the movement of the fluid and solid is determined by the rest of system through dynamical boundary conditions. The use of multi-scale techniques allows us to investigate the effect of the whole loop on the aneurysm dynamic. A three-dimensional fluid-structure interaction model for the aneurysm is developed and coupled to a mono-dimensional one for the remaining part of the cardiovascular system, where a point zero-dimensional model for the heart is provided. In this manner it is possible to achieve rigorous and quantitative investigations of the cardiovascular disease without loosing the system dynamic. In order to study this biomedical problem we use a monolithic fluid-structure interaction (FSI) model where the fluid and solid equations are solved together. The use of a monolithic solver allows us to handle the convergence issues caused by large deformations. By using this monolithic approach different solid and fluid regions are treated as a single continuum and the interface conditions are automatically taken into account. In this way the iterative process characteristic of the commonly used segregated approach, it is not needed any more.

In this work we investigate the potentialities of multi-scale engineering techniques to approach complex problems related to biomedical and biological fields. In particular we study the interaction between blood and blood vessel focusing on the presence of an aneurysm. The study of each component of the cardiovascular system is very difficult due to the fact that the movement of the fluid and solid is determined by the rest of system through dynamical boundary conditions. The use of multi-scale techniques allows us to investigate the effect of the whole loop on the aneurysm dynamic. A three-dimensional fluid-structure interaction model for the aneurysm is developed and coupled to a mono-dimensional one for the remaining part of the cardiovascular system, where a point zero-dimensional model for the heart is provided. In this manner it is possible to achieve rigorous and quantitative investigations of the cardiovascular disease without loosing the system dynamic. In order to study this biomedical problem we use a monolithic fluid-structure interaction (FSI) model where the fluid and solid equations are solved together. The use of a monolithic solver allows us to handle the convergence issues caused by large deformations. By using this monolithic approach different solid and fluid regions are treated as a single continuum and the interface conditions are automatically taken into account. In this way the iterative process characteristic of the commonly used segregated approach, it is not needed any more.

Verona is a town in Veneto Region (Italy) characterised by a high socio-economic status, but we register some health problems related to low income or social deprivation, such as unintentional carbon monoxide poisoning in private houses. Recently, indeed, there has been a rise in the number of accidents concerning immigrant populations. Since early 1990s, epidemiological informations in the matter weren?t complete and the number of cases was therefore probably underestimated. Presently no centralised system exists in Italy or in Veneto Region for recording the incidence of household CO poisoning. An ?Observatory on CO poisonings? was therefore activated in Verona Municipality in 1994 to overcome the problem of lacking data. The Observatory systematically collects data on cases of acute household CO poisoning occurring in the whole Verona area. These informations are used to assess public health interventions. During 13 years? activity 671 cases of CO poisoning and 22 deaths were recorded. The accidents were caused by the malfunctioning of home heating appliances. Statistics show a progressive increase in the number of not Italian involved in these episodes. Inspections revealed that immigrants often live in poor houses with unsafe systems or with extremely precarious heating systems. Data from this surveillance system on CO poisoning have shown that this is a public health problem involving immigrants much more often than local population. This system in real time supplies epidemiological and environmental data for improving public health intervention strategies. Such data collection systems could be useful to study other relevant problems of health disparities in lower socio-economical classes.

Verona is a town in Veneto Region (Italy) characterised by a high socio-economic status, but we register some health problems related to low income or social deprivation, such as unintentional carbon monoxide poisoning in private houses. Recently, indeed, there has been a rise in the number of accidents concerning immigrant populations. Since early 1990s, epidemiological informations in the matter weren?t complete and the number of cases was therefore probably underestimated. Presently no centralised system exists in Italy or in Veneto Region for recording the incidence of household CO poisoning. An ?Observatory on CO poisonings? was therefore activated in Verona Municipality in 1994 to overcome the problem of lacking data. The Observatory systematically collects data on cases of acute household CO poisoning occurring in the whole Verona area. These informations are used to assess public health interventions. During 13 years? activity 671 cases of CO poisoning and 22 deaths were recorded. The accidents were caused by the malfunctioning of home heating appliances. Statistics show a progressive increase in the number of not Italian involved in these episodes. Inspections revealed that immigrants often live in poor houses with unsafe systems or with extremely precarious heating systems. Data from this surveillance system on CO poisoning have shown that this is a public health problem involving immigrants much more often than local population. This system in real time supplies epidemiological and environmental data for improving public health intervention strategies. Such data collection systems could be useful to study other relevant problems of health disparities in lower socio-economical classes.

Optimal boundary control problems associated with the Navier-Stokes equations coupled with the energy equation have a wide and important range of applications. Velocity, pressure and temperature describe most systems and the control through their boundary conditions is the most common in their optimal design. Despite the fact that this field has been extensively studied, determining the optimal boundary control for a complex system of equations is still a difficult and time consuming task. In this work, we study a class of stationary optimal temperature and optimal flow control problems and their implementation. In order to implement the boundary control the boundary control problem is transformed into an extended distributed problem. This approach gives robusteness to the boundary control algorithm which can be solved by standard distributed control techniques over the extended part of the domain. Optimal control computations with distributed and boundary controls are presented by using a new multigrid approach for reliable and robust optimization. In fact the multigrid solver is based on a local Vanka-type solver for the Navier-Stokes, temperature and the adjoint system of equations. The solution is achieved by solving and relaxing element by element the optimal control problem which is formulated by using an embedded domain approach. The class of Vanka-type smoothers is characterized, in each smoothing step, by the solution of small local linear systems of equations in a Gauss-Seidel manner. In this work these solvers are applied to simple optimality systems and its adjoint system. The optimal solution is achieved by solving and relaxing element by element the optimal control problem. By using this technique only local subsystems are stored and solved which allows this method to be very effective in large problems where other solvers cannot satisfy memory and cpu requirements. Also the adjoint and the original system can be solved exactly over small domains and t

Optimal boundary control problems associated with the Navier-Stokes equations coupled with the energy equation have a wide and important range of applications. Velocity, pressure and temperature describe most systems and the control through their boundary conditions is the most common in their optimal design. Despite the fact that this field has been extensively studied, determining the optimal boundary control for a complex system of equations is still a difficult and time consuming task. In this work, we study a class of stationary optimal temperature and optimal flow control problems and their implementation. In order to implement the boundary control the boundary control problem is transformed into an extended distributed problem. This approach gives robusteness to the boundary control algorithm which can be solved by standard distributed control techniques over the extended part of the domain. Optimal control computations with distributed and boundary controls are presented by using a new multigrid approach for reliable and robust optimization. In fact the multigrid solver is based on a local Vanka-type solver for the Navier-Stokes, temperature and the adjoint system of equations. The solution is achieved by solving and relaxing element by element the optimal control problem which is formulated by using an embedded domain approach. The class of Vanka-type smoothers is characterized, in each smoothing step, by the solution of small local linear systems of equations in a Gauss-Seidel manner. In this work these solvers are applied to simple optimality systems and its adjoint system. The optimal solution is achieved by solving and relaxing element by element the optimal control problem. By using this technique only local subsystems are stored and solved which allows this method to be very effective in large problems where other solvers cannot satisfy memory and cpu requirements. Also the adjoint and the original system can be solved exactly over small domains and t

We consider the mathematical formulation, analysis, and the numerical solution of a time-dependent optimal control problem associated with the tracking of the velocity of a Navier-Stokes ow in a bounded two-dimensional domain through the adjustment of a distributed control. The existence of optimal solutions is proved and the first-order necessary conditions for optimality are used to derive an optimality system of partial differential equations whose solutions provide optimal states and controls. Semidiscrete-in-time and fully discrete space-time approximations are defined and their convergence to the exact optimal solutions is shown. A gradient method for the solution of the fully discrete equations is examined, as are its convergence properties. Finally, the results of some illustrative computational experiments are presented.

We consider the mathematical formulation, analysis, and the numerical solution of a time-dependent optimal control problem associated with the tracking of the velocity of a Navier-Stokes ow in a bounded two-dimensional domain through the adjustment of a distributed control. The existence of optimal solutions is proved and the first-order necessary conditions for optimality are used to derive an optimality system of partial differential equations whose solutions provide optimal states and controls. Semidiscrete-in-time and fully discrete space-time approximations are defined and their convergence to the exact optimal solutions is shown. A gradient method for the solution of the fully discrete equations is examined, as are its convergence properties. Finally, the results of some illustrative computational experiments are presented.