Papers by Antonietta Boniforti
Bioengineering, May 21, 2024
Fluids
Flow diverter stents (FDS) are increasingly used for the treatment of complex intracranial aneury... more Flow diverter stents (FDS) are increasingly used for the treatment of complex intracranial aneurysms such as fusiform, giant, or wide-neck aneurysms. The primary goal of these devices is to reconstruct the diseased vascular segment by diverting blood flow from the aneurysm. The resulting intra-aneurysmal flow reduction promotes progressive aneurysm thrombosis and healing of the disease. In the present study, a numerical investigation was performed for modeling blood flow inside a patient-specific intracranial aneurysm virtually treated with FDS. The aim of the study is to investigate the effects of FDS placement prior to the actual endovascular treatment and to compare the effectiveness of devices differing in porosity. Numerical simulations were performed under pulsatile flow conditions, taking into account the non-Newtonian behavior of blood. Two possible post-operative conditions with virtual stent deployment were simulated. Hemodynamic parameters were calculated and compared bet...
Sustainability
The knowledge of the simultaneous nodal pressure values in a water distribution network (WDN) can... more The knowledge of the simultaneous nodal pressure values in a water distribution network (WDN) can favor its correct management, with advantages for both water utilities and end users, and guarantee higher sustainability in the use of the water resource. However, monitoring pressure in all the nodes is not feasible, so it can be useful to develop methods that allow us to estimate the whole pressure field based on data from a limited number of nodes. For this purpose, the work employed an artificial neural network (ANN) as a machine-learning regression algorithm. Uncertainty of water demand is modeled through scaling laws, linking demand statistics to the number of users served by each node. Three groups of demand scenarios are generated by using a Latin Hypercube Random Sampling with three different cross-correlations matrices of the nodal demands. Each of the corresponding groups of pressure scenarios is employed for the training of an ANN, whose performance parameter is preliminari...
Sustainability
The knowledge of the simultaneous nodal pressure values in a water distribution network (WDN) can... more The knowledge of the simultaneous nodal pressure values in a water distribution network (WDN) can favor its correct management, with advantages for both water utilities and end users, and guarantee higher sustainability in the use of the water resource. However, monitoring pressure in all the nodes is not feasible, so it can be useful to develop methods that allow us to estimate the whole pressure field based on data from a limited number of nodes. For this purpose, the work employed an artificial neural network (ANN) as a machine-learning regression algorithm. Uncertainty of water demand is modeled through scaling laws, linking demand statistics to the number of users served by each node. Three groups of demand scenarios are generated by using a Latin Hypercube Random Sampling with three different cross-correlations matrices of the nodal demands. Each of the corresponding groups of pressure scenarios is employed for the training of an ANN, whose performance parameter is preliminari...
Fluids
Blood flow dynamics plays a crucial role in the growth and rupture of abdominal aortic aneurysms.... more Blood flow dynamics plays a crucial role in the growth and rupture of abdominal aortic aneurysms. The aim of this study was to analyze the possibility of predicting aneurysmal rupture by numerical investigations based on diagnostic images. The blood flow dynamics was analyzed in a patient-specific abdominal aortic aneurysm, reconstructed from CT images of an aneurysm while it was rupturing. The patient-specific geometry was virtually repaired in order to obtain a non-ruptured model representative of the geometry immediately preceding the rupture. To reproduce physiological conditions, numerical simulations were performed under pulsatile flow conditions, and blood was modelled as a non-Newtonian fluid, using the Carreau rheological model. Hemodynamic parameters that influence the rupture of the aneurysm were investigated, and their possible association with vascular disease was discussed. The results of the numerical simulations indicated regions of slow recirculation and low values ...
In this paper the dynamics of a layered fluid system, constituted by two superimposed immiscible ... more In this paper the dynamics of a layered fluid system, constituted by two superimposed immiscible liquid layers inside a moving container, is considered. Such layered fluid system presents two moving boundaries: the separation surface and the free surface. The motion imposed to the container an oscillating rotation with given amplitude and frequency generates waves on the moving surfaces, whose dynamics is analysed by means of a suitable visualisation device. Several wave configurations are obtained by varying the angular frequency of the exciting motion and some of them compared with those obtained by numerical simulations.
In this paper a low dimensional dynamical system is used to model the local evolution of a distur... more In this paper a low dimensional dynamical system is used to model the local evolution of a disturbance superimposed on a basic shear flow. In particular, non-linear interactions between planar waves and oblique waves which travel phase-locked in the far wake of a cylinder are simulated. At this aim a low- dimensional dynamical system is derived by imposing the respect of a non- linear truncation condition together with those phase-locked condition experimentally observed. The numerical results are compared with some recent experimental results obtained analysing the dynamics of a cylinder far wake. Different experimental conditions were modelled by dynamical systems defined by one or more coupled triadic systems
Applied Sciences, 2019
We investigated the blood flow patterns and the hemodynamics associated with an abdominal aortic ... more We investigated the blood flow patterns and the hemodynamics associated with an abdominal aortic aneurysm detected in an in vitro measurement campaign performed in a laboratory model of an aneurysm with rigid walls and an axisymmetric shape. Experiments were run in steady flow conditions and by varying the Reynolds number in the range 410 < Re < 2650. High spatial and temporal resolution 2D optical measurements of the velocity field were obtained through a particle tracking technique known as Hybrid Lagrangian Particle Tracking. Conversely to classical Particle Image Velocimetry, both the fluid particle trajectories and the instantaneous and time-averaged velocity fields are provided without constraints on the grid size and very close to the vessel boundary. All the most relevant quantities needed to investigate the flow features were evaluated, and in particular, we focused on the wall shear stress distribution both in the healthy aortic portion and within the aneurysm. Resul...
Proceedings of the International Workshop on Environmental Hydraulics, IWEH09, 29 & 30 October 2009, Valencia, Spain, 2009
In this paper a mathematical model for 3D turbidity currents has been presented. The model consis... more In this paper a mathematical model for 3D turbidity currents has been presented. The model consists in a system of partial differential equations in conservative form, formulated in the framework of the shallow water equations and it accounts for the main features of the turbidity currents: entrainment of environment fluid, settling and resuspension of particles, variation of density. A numerical investigation has been performed to assess the influence of the settling of particles on the turbidity current. To this aim different turbidity currents have been simulated, with the same excess density and initial volume, but realized with silicon carbide particles with increasing diameter. Numerical results are compared with experimental results by La Rocca et al.[8]. The agreement is fairly good and shows the ability of the proposed model in reproducing the main features of the physical phenomenon
Journal of Hydraulic Research, 2012
Immersive Participationentails massive participatory activities in the Internetengaging people, p... more Immersive Participationentails massive participatory activities in the Internetengaging people, places and objects. This ispremised on the existence of an Internet of Things infrastructure supporting applications and services with the same richness of experience as the World Wide Web. This in turn presupposes the existence of models for establishing and maintaining context relations. Where these models do exist, they impose a limited interpretation of context relations in the presence of the inherent heterogeneous and dynamic characteristics of the supporting information. In this paper we introduce an approach towards establishing context relations through the use of an improved context relational model permitting a wider, more complete range of application specific scenarios. Additionally, wederive a measure of context proximity that considers the situation, attributes, relations, accuracy and heterogeneity of both the underlying information and the vast array of requirements for metrics supporting application problem domains.
Fluid Dynamics Research, 2000
In this paper a theoretical and experimental analysis of sloshing in 2D and 3D free-surface conÿg... more In this paper a theoretical and experimental analysis of sloshing in 2D and 3D free-surface conÿgurations is performed. In particular, the case of a tank rotating around a horizontal axis has been considered. The uid is assumed to be incompressible and inviscid. A fully nonlinear mathematical model is deÿned by applying the variational method to the sloshing. The damping of gravity waves has been accounted by introducing a suitable dissipation function from which generalized dissipative forces are derived. A modal decomposition is then adopted for the unknowns and a dynamical system is derived to describe the evolution of the physical system. An experimental technique has been applied to select the leading modes, whose evolution characterizes the physical process, i.e. captures the most of the kinetic energy of the process. A very good agreement between experimental and numerical results conÿrms the validity of the methodological approach followed.
Fluid Dynamics Research, 2002
In this work a theoretical and experimental investigation is performed on the sloshing of two imm... more In this work a theoretical and experimental investigation is performed on the sloshing of two immiscible liquid layers inside of a closed square-section tank. By applying a variational approach to the potential formulation of the fluid motion, a nonlinear dynamical system is derived applying the Lagrange equations to the Lagrangian of motion defined in terms of suitable generalised coordinates. These coordinates are the time depending coefficients of the modal expansions adopted for the separation surface of the two fluids and for the velocity potentials of the fluid layers. Dissipative effects are taken into account by considering generalised dissipative forces derived by a dissipative model extensively treated in the paper. Numerical integration of the dynamical system furnish solutions which well reproduce the examined experimental configurations.
Journal of Zhejiang University SCIENCE A, 2015
Submerged vanes are low-height flow-training structures emerging from the riverbed with a suitabl... more Submerged vanes are low-height flow-training structures emerging from the riverbed with a suitable angle of attack to the incoming flow. These structures redirect the stream flow and modify erosion and depositional rates in the bottom and in the banks of a river as a result of the secondary currents generated by their installation. For this reason they have many applications in river hydraulics for controlling river bed morphology. An experimental investigation is carried out to compare the efficiency of sheet-piling vanes versus thin plane ones in controlling sediment redistribution in the channel bed. In particular, experimental tests were carried out within a straight water channel, in conditions of bed load motion. The morphology of the river bed both in the area close to the structure and in the far field was examined at different angles of attack of the vane to the incoming flow and at different values of the submergence parameter, which is the ratio between the height of the water above the structure and the water level. The experimental results show that both the shape of the vanes as well as the angle of attack affect their performance in terms of the effects on the bed morphology, especially for greater submergence parameters. Specifically, plane and sheet-piling vanes produce comparable remodelings of the channel bed in the downstream region, but when the attack angle is increased, the thin plane vane causes deeper scour holes close to the structure. This last effect is probably due to the increased erosive capacity of the horseshoe vortex associated with the plane vane, while the uneven surface of the sheet-piling vane mitigates the erosive strength of that vortex.
Journal of Zhejiang University-SCIENCE A, 2021
Hemodynamics plays a crucial role in the growth of an abdominal aortic aneurysm (AAA) and its pos... more Hemodynamics plays a crucial role in the growth of an abdominal aortic aneurysm (AAA) and its possible rupture. Due to the serious consequences that arise from the aneurysm rupture, the ability to predict its evolution and the need for surgery are of primary importance in the medical field. Furthermore, the presence of intraluminal thrombus (ILT) strongly affects the evolution of the pathology. In this study, we analyzed the influence of hemodynamics on the growth and possible rupture of AAAs. Numerical investigations of pulsatile non-Newtonian blood flow were performed in six patient-specific AAAs reconstructed from diagnostic images, having different sizes and shapes, and with or without ILT. Wall shear stress and vorticity distribution in the bulge and their evolution during the cardiac cycle were analyzed. The results indicate that blood flow dynamics acts synergistically with atherosclerotic degeneration in the development of the disease. The high surface complexity and tortuosity of the aneurysms significantly affect the blood motion, and the presence of inflection in the aneurysm centerline has a noticeable effect on the vortex dynamics. Links between regions of slow recirculating flows, low values of time-averaged wall shear stress, high values of oscillatory shear index, and zones of ILT deposition were found. In the absence of ILT, possible thrombus accumulation areas and consequent aneurysm growth were identified. The findings of this study highlight the importance of hemodynamics in assessing the vulnerability of the aortic wall and underline the crucial role of patient-specific investigations in predicting the rupture of individual aneurysms.
A numerical approach for generating a limited number of water demand scenarios and 12 estimating ... more A numerical approach for generating a limited number of water demand scenarios and 12 estimating their occurrence probabilities in a Water Distribution Network (WDN) is proposed. This 13 approach makes use of the demand scaling laws in order to consider the natural variability and 14 spatial correlation of nodal consumptions. The scaling laws are employed to determine the statistics 15 of nodal consumption as a function of the number of users and the main statistical features of the 16 unitary user's demand. Besides, consumption at each node is considered to follow a Gamma 17 probability distribution. A high number of groups of cross-correlated demands, i.e. scenarios, for 18 the entire network were generated using Latin Hypercube Sampling (LHS) and the numerical 19 procedure proposed by Iman and Conover. The Kantorovich distance is used to reduce the number 20 of scenarios and estimate their corresponding probabilities, while keeping the statistical information 21 on nodal cons...
In this paper a theoretical and experimental investigation on the slosh- ing of two liquid layers... more In this paper a theoretical and experimental investigation on the slosh- ing of two liquid layers with a free-surface is performed. The mathemati- cal model is obtained by applying the Lagrangian variational formulation to the potential formulation of the fluid motion and a dynamical sys- tem which describes the dynamics of motion of the separation surface is derived. In order to account the damping of the motion, generalised dissipative forces are considered. To this aim, the logarithmic decrement coefficients are estimated by means of a wavelet analysis performed on the experimental free oscillations of the fluid system. The numerical integra- tion of the mathematical model gives results which are in good agreement with the experimental results. 1I ntroduction The aim of this paper consists in investigating the motion of the separation surface between two layers of immiscible liquids inside of a prismatic container which can rotate around a horizontal axis. Colored water and trans...
In this work a theoretical investigation is performed on modelling interfacial and surface waves ... more In this work a theoretical investigation is performed on modelling interfacial and surface waves in a layered fluid system. The physical system consists of two immiscible liquid layers of different densities ρ 1 >ρ 2 with an interfacial and a free surface, inside of a prismatic-section tank. By using the potential formulation of the fluid motion, a nonlinear system of partial differential equations is derived applying the Hamiltonian formulation for irrotational flows of two fluids of different density subject to conservative force. As a consequence of the assumption of potential velocity, the dynamics of the system can be described in terms of variables evaluated only at the boundary of the fluid system, namely the separation surface and the free surface. This Hamiltonian formulation permits to define the evolution equations of the system in a canonical form by using the functional derivatives.
Nonlinear Oscillations, 2003
UDC 532.595 In this work, we analyze the stability of a gravity wave generated on the separation ... more UDC 532.595 In this work, we analyze the stability of a gravity wave generated on the separation surface of two immiscible liquids inside a moving container and perturbed by a capillary wave. Such a phenomenon is experimentally observed when the amplitude and the frequency of the motion imposed to the container attain certain values. The evolution of the system is described by the variational principle. We assume that the motion of the system is decomposed into two modes: the gravity mode and the capillary mode. With suitable scaling assumptions, it is possible to show that the evolution of the gravity mode is determined by the forcing motion, while the capillary mode is excited by the nonlinear interactions between the capillary and gravity modes. Finally, an analytic dispersion relation is obtained for the pulsation of the capillary mode. This relation is a function of several quantities, all depending on the capillary wave number and the characteristics of the exciting motion.
Nonlinear Oscillations, 2003
In this work, a theoretical investigation is performed on modeling interfacial and surface waves ... more In this work, a theoretical investigation is performed on modeling interfacial and surface waves in a layered fluid system. The physical system consists of two immiscible liquid layers of different densities ?1 > ?2 with an interfacial surface and a free surface, inside a prismatic-section tank. On the basis of the potential formulation of the fluid motion, we derive a
Uploads
Papers by Antonietta Boniforti