Linear stability analysis of a time-divergent slamming flow

When a liquid slams into a solid, the intermediate gas is squeezed out at a speed that diverges when approaching the moment of impact. Although there is mounting experimental evidence that instabilities form on the liquid interface during such an event, understanding of the nature of these instabilities is limited. This study therefore addresses the stability of a liquid–gas interface with surface tension, subject to a diverging flow in the gas phase, where the liquid and the gas phase are both represented as potential fluids. We perform a Kelvin–Helmholtz-type linear modal stability analysis of the surface to obtain an amplitude equation that is subsequently analysed in detail and applied to two cases of interest for impact problems, namely, the parallel impact of a wave onto a vertical wall, and the impact of a horizontal plate onto a liquid surface. In both cases we find that long wavelengths are stabilised considerably in comparison with what may be expected based upon classical knowledge of the stability of interfaces subject to a constant gas flow. In the former case, this leads to the prediction of a marginally stable wavelength that is completely absent in the classical analysis. For the latter we find much resemblance to the classical case, with the connotation that the instability is suppressed for smaller disk sizes. The study ends with a discussion of the influence of gas viscosity and gas compressibility on the respective stability diagrams.

Modelling multiple-simultaneous impact problems with a nonlinear smooth approach: pool/billiard application

Smooth approaches are able to model reasonably well contact/impact events between two bodies, showing some peculiarities when dealing with certain geometries and arising certain issues with the detection of the initial instant of contact. The characterization of multiple-simultaneous interaction systems, considering (or not) energy dissipation phenomena (mainly friction), is always an interesting research topic, addressed from different perspectives. In the present work, the process of design, optimization and verification of a multiple-impact, day-to-day multibody novel model is shown. Specifically, we have decided to focus on a pool/billiard game due to its geometry simplicity. The model involves several balls moving freely and rolling, suffering different kinds of contacts/impacts among them and against the cushions and the cloth. In this system, the proper modelling of both contact and friction forces in the multiple, simultaneous contacts and impacts events is critical to obtain consistent results. In addition, these forces are complicated to model because of its nonlinear behaviour. The different existing approaches when dealing with multiple-contact events are briefly described, along with their most distinctive features. Then, the interactions identified on the model are implemented using several nonlinear contact-force models, following a smooth-based approach and considering friction phenomena, aiming at determining the most suitable set of both contact and friction force models for each of these implemented interactions, which take place simultaneously, thus resulting in a complex system with multiple impacts. Subsequently, the solving method that provides the most accurate results at the minimum computational cost is determined by testing a simple shot. Finally, the different interactions on the model are verified using experimental results and previous works. One of the main goals of this work is to show the some of the issues that arise when dealing with multiple-simultaneous impact multibody systems from a smooth-contact approach, and how researchers can deal with them.

A REVIEW ON THE IMPACT OF THE COVID-19 PANDEMIC ON THE HEALTH CARE SECTOR

The global crisis of the present era, the COVID-19 pandemic, has changed given new normal ways in many of the sectors. The present review highlights the impact, problems, and challenges faced by major areas of the health care sector due to pandemics and also addresses some of the aspects of upcoming approaches. The healthcare sector is the one sector that is on-demand since this COVID-19 pandemic raised. During the initial period, there was disruption of various services provided by the health care sector due to supply chain management issues and reduction in demand by consumers, quarantine, and lockdown period. The healthcare workers also confronted a huge challenge due to the increased number of cases and shortage of amenities and safety measures. This significantly affected even COVID-19 patients and the general public suffering from other diseases. To fight this issue, research and development (RandD) in pharmaceutical industries with great efforts to explore molecules and save many lives. Gradually innovative ways to strengthen and combat pandemics started emerging. Numeral ways and rules were adopted to prevent, diagnose and cure the disease. Artificial intelligence technology has emerged as one of the boons to address many of the unresolved or time-consuming mysteries. All the divisions of health care sectors have started working more efficiently with adopted new strategies to face future challenges.

Open Innovation Experiences Developed in the Hub Center Project for the Solution of High Impact Problems of the Central Region of the Country

This article allows us to externalize the experiences mainly of the challenges of open innovation developed in the cities of Riobamba, Latacunga and Ambato, understood these cities as the HUB's area of influence, in addition, to refer to the current situation as organizations that promote solutions to these problems existing ones that have been confronted taking innovation as the main instrument to provide solutions. The main objective of this review article is to refer to the open innovation experiences that the HUB Center has carried out at the time of its management, specified in the development of the document. The development of this work was done through the exploration of information from authors who have already treated these issues with another perspective and with other ways of doing things, with enough experience in their field, also the deductive study method allows to go from a general context to a specific one, and according to the requirements that this research estimates. The HUB Center is a networked space with 8 Higher Education Institutions plus the Ecuadorian Corporation for Research Development and the Academy that are members of this network, through these institutions and with the articulation of the HUB, local development is promoted from the academy to the productive and social sectors supported by the central government and the local governments of each province. Keywords: HUB Center, open innovation, high impact problems, higher education institutions, zone 3, innovation challenges. Resumen Este articulo permite exteriorizar las experiencias principalmente de los retos de innovación abierta desarrollados en las ciudades de Riobamba, Latacunga y Ambato, entendidas estas ciudades como la zona de influencia del HUB, además, referir la situación actual en cuanto organizaciones que promuevan soluciones a esas problemáticas existentes que se han afrontado tomando a la innovación como principal instrumento para dar soluciones. El objetivo principal de este artículo de revisión es referir las experiencias de innovación abierta que el HUB Centro ha realizado en el tiempo de su gestión, especificadas en el desarrollo del documento. El desarrollo de este trabajo se lo realizo mediante la exploración de información de autores que ya han tratado estos temas con otra perspectiva y con otras formas de hacer las cosas, con una experiencia basta en su campo, asimismo el método de estudio deductivo permite ir de un contexto general a uno concreto, y de acuerdo con los requerimientos que esta investigación estima. El HUB Centro es un espacio que funciona en red con 8 Instituciones de Educación Superior más la Corporación Ecuatoriana para el Desarrollo de la Investigación y la Academia que son miembros de esta red, mediante estas instituciones y con la articulación del HUB se promueven el desarrollo local desde la academia hacia los sectores productivos y sociales apoyados por el gobierno central y los gobiernos locales de cada provincia. Palabras clave: HUB Centro, innovación abierta, problemas de alto impacto, instituciones de educación superior, zona 3, retos de innovación.

High Order Godunov Type Multimesh Method for 3d Impact Problems of Elastoplastic Media

A numerical method for calculating the three-dimensional processes of impact interaction of elastoplastic bodies under large displacements and deformations based on the multi mesh sharp interface method and modified Godunov scheme is presented. To integrate the equations of dynamics of an elastoplastic medium, the principle of splitting in space and in physical processes is used. The solutions of the Riemann problem for first and second order accuracy for compact stencil for an elastic medium in the case of an arbitrary stress state are obtained and presented, which are used at the “predictor” step of the Godunov scheme. A modification of the scheme is described that allows one to obtain solutions in smoothness domains with a second order of accuracy on a compact stencil for moving Eulerian-Lagrangian grids. Modification is performed by converging the areas of influence of the differential and difference problems for the Riemann’s solver. The “corrector” step remains unchanged for both the first and second order accuracy schemes. Three types of difference grids are used. The first – a moving surface grid – consists of a continuous set of triangles that limit and accompany the movement of bodies; the size and number of triangles in the process of deformation and movement of the body can change. The second – a regular fixed Eulerian grid – is limited to a surface grid; separately built for each body; integration of equations takes place on this grid; the number of cells in this grid can change as the body moves. The third grid is a set of local Eulerian-Lagrangian grids attached to each moving triangle of the surface from the side of the bodies and allowing obtain the parameters on the boundary and contact surfaces. The values of the underdetermined parameters in cell’s centers near the contact boundaries on all types of grids are interpolated. Comparison of the obtained solutions with the known solutions by the Eulerian-Lagrangian and Lagrangian methods, as well as with experimental data, shows the efficiency and sufficient accuracy of the presented three-dimensional methodology.