Comparative analyses between the zero-inertia and fully dynamic models of the shallow water equations for unsteady overland flow propagation

The shallow water equations are a mathematical tool widely applied for the simulation of flow routing in rivers and floodplains, as well as for flood inundation mapping. The interest of many researchers has been focused on the study of simplified forms of the original set of equations. One of the most commonly applied simplifications consists in neglecting the inertial terms. The effects of such a choice on the outputs of the simulations of flooding events are controversial and are an important topic of debate. In the present paper, two numerical models recently proposed for the solution of the complete and zero-inertia forms of the shallow water equations, are applied to several unsteady flow routing scenarios. We simulate synthetic and laboratory scenarios of unsteady flow routing, starting from very simple geometries and gradually moving towards complex topographies. Unlike the studies of the range of validity of the zero-inertia model, based on a small perturbation of the linearized flow model, in unsteady flow propagation over irregular topographies, it is more difficult to specify criteria for the applicability of the simplified set of equations. Analyzing the role of the terms in the momentum equations, we try to understand the effect of neglecting the inertial terms in the zero-inertia formulation. We also analyze the computational costs

Urban Flood Prediction through GIS-Based Dual-Coupled Hydraulic Models

Propagation of pluvial floods in urban areas, occurring with return time periods of few years, can be well solved using dual models accounting for the mutual relationship between the water level in the streets and the discharges inside the sewer pipes. The extended WEC-flood model (EWEC), based on the use of unstructured triangular meshes and a diffusive formulation of the momentum equations in both the 2D and the 1D lower domains, is presented along with its novelty, limits, and advantages. The model is then applied to a small computational domain in the Palermo area, where only some 'hard' data given by one rain gauge has been used for calibration and validation, along with other 'soft' data like yes/no surcharge observations and water depths available from photos and interviews. Model input data are mainly geometrical parameters, and calibration parameters are restricted only to average Manning coefficients. In the test case a very good validation has been obtained of three historical events using the EWEC model, with only one average Manning coefficient calibrated using other two historical events

Inserimento di restringimenti e ponti in un modello diffusivo 2D di acque basse

Gli effetti su una corrente, causati dalle pile di un ponte, o più in generale da strutture che riducono la sezione trasversale dell’alveo, risultano di particolare interesse per le variazioni idrometriche che comportano alla corrente stessa. Nonostante i numerosi studi teorici e sperimentali di letteratura, l’attuale modellistica numerica diffusiva non integra la presenza di tali manufatti nelle proprie tecniche risolutive. Nella presente memoria viene presentata la metodologia implementata nel modello diffusivo bidimensionale FLOW2D per la valutazione del rigurgito provocato da restringimenti della sezione trasversale, nonché dalla presenza delle campate. I profili di rigurgito ottenuti con il modello proposto, in alcuni casi test, sono stati confrontati con le soluzioni esatte e con i profili di un modello completo. Inoltre, i risultati della metodologia proposta si sono dimostrati in buon accordo con i dati di pieno campo rilevati in un venturimetro

ADCP velocity profiles analisys in the Castellammare gulf

Velocity profiles have been collected in three points within the Castellammare gulf at around 1500 m far from the coastline. This area is characterized by the presence of an aquaculture farm that positioned 5 floating cages in this zone. The impact of this activity on the environment strictly depends on the currents and water exchange. The general aim of this research is the characterization of the circulation characteristics of this area. The analysis of the free surface oscillations shows the typical behaviour of tide forcing, with high minima and maxima during the night, due to the higher moon attraction during these hours compared with the morning hours. A prevalent current direction from South-West to North-East has been recorded at each depth. This direction is almost parallel to the coastline. This behaviour is probably determined by morphology of the area and the general circulation of the Castellammare gulf

Calcolo della portata di piena con modello bidimensionale non lineare

Si propone un modello bidimensionale di trasformazione afflussi-deflussi per il calcolo della piena in una sezione di un corso d\u2019acqua. Il bacino idrografico \ue8 rappresentato da una mesh triangolare non strutturata. L\u2019input del modello \ue8 costituito dalle piogge lorde, trasformate in piogge nette mediante l\u2019equazione integrata di Horton. Il calcolo della propagazione idraulica nei diversi rami della rete idrografica consente di abbandonare le ipotesi di stazionariet\ue0 e di linearit\ue0, ordinariamente adottate nell\u2019idrologia delle piene. Il modello proposto viene calibrato ed applicato ad un bacino idrografico di un affluente del fiume Tevere per il quale si dispongono di alcuni idrogrammi di piena e delle relative piogge

Wind- and tide-induced currents in the Stagnone Lagoon (Sicily)

The hydrodynamic circulation is analyzed in the coastal lagoon of Stagnone di Marsala, a natural reserve located in the north-western part of Sicily, using both experimental measurements and numerical simulations. Field measurements of velocities and water levels, carried out using an ultrasound sensor (3D), are used to validate the numerical model. A 3D finite-volume model is used to solve the Reynolds-averaged momentum and mass balance differential equations on a curvilinear structured grid, employing the k–ε turbulence model for the Reynolds stresses. The numerical analysis allows to identify the relative contribution of the forces affecting the hydrodynamic circulation inside the lagoon. In the simulations only wind and tide forces are considered, neglecting the effects of water density changes. Two different conditions are considered. In the first both the wind stress over the free-surface and the tidal motion are imposed. In the second the wind action is neglected, to separately analyze the tide-induced circulation. The comparison between the two test cases highlights the fundamental role of the wind on the hydrodynamics of the Stagnone lagoon, producing a strong vertical recirculation pattern that is not observed when the flow is driven by tides only

Experimental determination of <10 10>/ Ψ tilt grain boundary energies in ice

Ice grain boundary energies γgb relative to the free surface energy γs were determined by studying the topographic details revealed by plastic replicas of the ice grain boundary groove-free surface with a Laser Confocal 3D Microscope. The samples analyzed were high purity ice bicrystals, with ‹101– 0›/Ψ tilt grain boundaries, annealed at –18 o C. Values obtained of γgb/γs were analyzed using coincidence site lattice (CSL) theory. Significant correspondence was found between the γgb/γs values and the planar density of coincident sites on the interface plane. The results show that γgb/γs depends on the GB inclination and may be up to one order of magnitude different.http://dx.doi.org/10.5539/jmsr.v3n1p69publishedVersionFil: Druetta, Esteban. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: Nasello, Olga B. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: Di Prinzio, Carlos L. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: Nasello, Olga B. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Di Prinzio, Carlos L. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFísica de los Materiales Condensado

Designing Hydrogel-Based Bone-On-Chips for Personalized Medicine

The recent development of bone-on-chips (BOCs) holds the main advantage of requiring a low quantity of cells and material, compared to traditional In Vitro models. By incorporating hydrogels within BOCs, the culture system moved to a three dimensional culture environment for cells which is more representative of bone tissue matrix and function. The fundamental components of hydrogel-based BOCs, namely the cellular sources, the hydrogel and the culture chamber, have been tuned to mimic the hematopoietic niche in the bone aspirate marrow, cancer bone metastasis and osteo/chondrogenic differentiation. In this review, we examine the entire process of developing hydrogel-based BOCs to model In Vitro a patient specific situation. First, we provide bone biological understanding for BOCs design and then how hydrogel structural and mechanical properties can be tuned to meet those requirements. This is followed by a review on hydrogel-based BOCs, developed in the last 10 years, in terms of culture chamber design, hydrogel and cell source used. Finally, we provide guidelines for the definition of personalized pathological and physiological bone microenvironments. This review covers the information on bone, hydrogel and BOC that are required to develop personalized therapies for bone disease, by recreating clinically relevant scenarii in miniaturized device

Progettazione di una cassa d’espansione e determinazione della riduzione del rischio idraulico con modellazione 2D

Nell’articolo si studia l’effetto di una cassa d’espansione posta a monte di un’area fluviale soggetta a rischio idraulico. Lo strumento utilizzato è un software bidimensionale sviluppato per simulare la propagazione delle piene fluviali. Il dominio di calcolo è rappresentato da una mesh triangolare non strutturata con una maggiore densità di elementi all’interno dell’alveo e nelle zone immediatamente limitrofe. Per facilitare gli accumuli temporanei di parte dei volumi di piena, si ipotizza la costruzione di un restringimento dell’alveo per mezzo di due pareti verticali che avvicinano le sponde fluviali. Durante la piena, il passaggio per lo stato critico nel restringimento provoca un rigurgito a monte, e quindi un agevole riempimento della cassa d’espansione. La perimetrazione di tale cassa è definita con la costruzione di un rilevato arginale di adeguata altezza. Per meglio simulare il rigurgito a monte della strozzatura, si introduce una scabrezza equivalente negli elementi della strozzatura, per riprodurre le perdite di carico nel restringimento e nel successivo risalto idraulico, malgrado l’ipotesi diffusiva utilizzata nel software di calcolo. La conoscenza delle aree allagate in due eventi di piena storici e dei due relativi idrogrammi di piena, ha consentito la determinazione del coefficiente di Manning quale misura della scabrezza in alveo e fuori alveo. Mediante l’applicazione del modello proposto è possibile validare sia il posizionamento degli argini a monte del restringimento per il contenimento della piena, sia la riduzione delle aree di valle soggette a rischio idraulico

Bone regeneration in patient-specific scaffolds from microfluidics to computational simulation

Los trastornos musculoesqueléticos y sus correspondientes enfermedades óseas son una de las principales causas de dolor y discapacidad, así como una carga social y económica para nuestra sociedad. Cuando la función articular se ve afectada o los defectos óseos son demasiado grandes para los injertos óseos, los implantes protésicos son el método estándar para tratar los trastornos musculoesqueléticos graves, aunque existe la necesidad clínica de que los implantes permanezcan activos durante un período de tiempo más largo y reduzcan las tasas de revisión. Para abordar la mayor durabilidad de los implantes ortopédicos, recientemente han surgido implantes impresos en tres dimensiones (3D) para fabricar superficies porosas específicas del paciente en la superficie del hueso-implante, mejorando así la fijación biológica del implante. La traslación de los principios de la medicina regenerativa a la ortopedia permitiría definir una nueva generación de implantes que completen la transición de materiales inertes a andamios bioactivos que guíen el proceso de regeneración ósea. A corto plazo, es probable que los andamios ortopédicos regenerativos impresos en 3D aumenten la vida útil del implante, mientras que a largo plazo puedan degradarse una vez que el tejido huésped esté completamente reparado. El objetivo global de esta tesis es evaluar el potencial regenerativo asociado a los andamiajes óseos impresos en 3D para aplicaciones ortopédicas específicas del paciente.Para ello, el primer estudio tuvo como objetivo determinar el papel del entorno mecánico del huésped en el proceso de regeneración ósea guiado por andamios óseos impresos en 3D en aplicaciones de carga. Se desarrolló un modelo computacional de regeneración ósea impulsada por un mecanismo en andamios porosos y se basó en la especificidad del sujeto, el sitio de implantación y la sensibilidad al entorno mecánico. A continuación, se simuló el crecimiento óseo en el interior de andamiajes porosos de titanio implantados en el fémur distal y la tibia proximal de tres cabras y se comparó con los resultados experimentales. Los resultados mostraron que el crecimiento óseo en el interior cambió de un patrón de distribución homogéneo, cuando los andamios estaban en contacto con el hueso trabecular, a un crecimiento óseo localizado cuando los andamios se implantaron en una ubicación diafisaria. En general, la dependencia de la respuesta osteogénica de la biomecánica del huésped sugirió que, desde una perspectiva mecánica, el potencial regenerativo dependía tanto del andamio como del entorno del huésped.El segundo estudio de esta tesis tuvo como objetivo evaluar la actividad osteogénica específica del paciente en un entorno controlado in vitro donde las células óseas humanas, aisladas de sujetos individuales, imitan los rasgos esenciales del proceso de formación ósea. Los sistemas in vitro tradicionales ya permitieron demostrar que los osteoblastos humanos primarios embebidos en una matriz fibrada de colágeno se diferencian en osteocitos en condiciones específicas. Por lo tanto, se planteó la hipótesis de que la traslación de este entorno a la escala de órgano en un chip crea una unidad funcional mínima para recapitular la maduración de los osteoblastos hacia los osteocitos y la mineralización de la matriz. Con este propósito, se sembraron osteoblastos humanos primarios en un hidrogel de colágeno de tipo I, para conocer mejor el papel de la densidad de siembra de células en su diferenciación a osteocitos. Los resultados muestran que las células cultivadas a mayor densidad aumentan la longitud de la dendrita con el tiempo, dejan de proliferar, exhiben morfología dendrítica, regulan positivamente la actividad de la fosfatasa alcalina y expresan marcadores de osteocitos. Este estudio reveló que los sistemas de microfluídica son una estrategia funcional que permite crear un modelo de tejido óseo específico del paciente e investigar el potencial osteogénico individual de las células óseas del paciente.En conjunto, los resultados de esta tesis enfatizan la importancia de utilizar un sistema de modelado múltiple al investigar el proceso de regeneración in vivo guiado por armazones óseos específicos adecuados al paciente. Ambos actores de una estrategia regenerativa libre de células in situ, a saber, el andamio y el paciente, tienen un efecto significativo en el resultado regenerativo final y necesitan ser modelados. Las técnicas avanzadas de in vitro e in silico, combinadas con datos de in vivo, evalúan aspectos distintivos del proceso de regeneración ósea para aplicaciones específicas del paciente. Las futuras estrategias personalizadas de ingeniería de tejidos podrían depender de la integración de esos modelos para mitigar en última instancia la variabilidad en el proceso de regeneración ósea guiado por un andamio específico para el paciente.<br /