1,721,458 research outputs found
Creación de lealtad en hotelería independiente : los recursos humanos son la clave
No full textFil: Tavelli, Mariela Verónica. Universidad de San Andrés. Escuela de Negocios; Argentina
Safety in road tunnels
No full textThis chapter briefly presents the main issues related to the safety inside road tunnels. Fires, events with potentially catastrophic consequences within these infrastructures, are concisely introduced
The fire tests in the morgex north tunnel
No full textAfter presenting the Morgex North tunnel, location of the full-scale fire tests, the choices made for the implementation of the fire test, made up by two fire scenarios, are deeply described. The idea of this part of the book is to give possible stakeholders useful suggestions in order to guide them in the preparation of a similar experience. Indications are given about fire scenarios and their preparation, safety issues, materials and equipment, preparation and location of measuring instruments
The research project and partners involved
No full textIn this chapter the authors introduce how fires in tunnels can be studied using CFD models, explaining the reasons behind the research project and the importance to perform full-scale fire tests in order to better understand and investigate these events. Finally, the subjects involved in project (Politecnico di Milano, Corpo Valdostano dei Vigili del Fuoco, RAV—Autostrade Spa) are presented
The test results
No full textIn this chapter are presented the experiments and experimental measurements obtained in the two full-scale fire tests performed in the Morgex North tunnel, where both the HRR and ventilation velocity were measured as a function of time. It is initially described how the fire scenarios were designed and operated, then the obtained experimental results are presented and compared to the numerical predictions of CFD simulations of the same fire scenarios. In this chapter the discussion is initially focused on the comparison with analytical models and empirical correlations based on theoretical analysis and literature measurements obtained in other tunnel fire tests. The Morgex fire tests allowed to collect different measurements (temperature, air velocity, smoke composition, pollutant species) useful for validating and improving new and existing CFD codes and for testing the real behaviour of a tunnel and its safety systems during a diesel oil fire with a significant Heat Release Rate (HRR)
Conclusions
No full textIn this book new full-scale tunnel fire experimental results are presented and discussed. The tests took place in the Morgex North tunnel of the A5 highway (Italy). The first part of the book describes how to set up full-scale fire tests inside an existing tunnels. Indications are given about fire scenarios and their preparation, safety issues, materials and equipment, preparation of tunnel sections and measuring instruments
Evaluation of the consequences on the users safety
No full textIn this chapter it is introduced a simple methodology for the quantitative assessment of the severity of the expected consequences of a tunnel fire that can be applied in any complex environment. The proposed methodology was applied to the Morgex North tunnel to show its potentiality for evaluating the effect of different geometric characteristics on the safety performances of a tunnel in the event of an unwanted fire
High order semi-implicit schemes for viscous compressible flows in 3D
No full textIn this article we present a high order cell-centered numerical scheme in space and time for the solution of the compressible Navier-Stokes equations. To deal with multiscale phenomena induced by the different speeds of acoustic and material waves, we propose a semi-implicit time discretization which allows the CFL-stability condition to be independent of the fast sound speed, hence improving the efficiency of the solver. This is particularly well suited for applications in the low Mach regime with a rather small fluid velocity, where the governing equations tend to the incompressible model. The momentum equation is inserted into the energy equation yielding an elliptic equation on the pressure. The class of implicit-explicit (IMEX) time integrators is then used to ensure asymptotic preserving properties of the numerical method and to improve time accuracy. High order in space is achieved relying on implicit finite difference and explicit CWENO reconstruction operators, that ultimately lead to a fully quadrature-free scheme. To relax the severe parabolic restriction on the maximum admissible time step related to viscous contributions, a novel implicit discretization of the diffusive terms is designed. A variational approach based on the discontinuous Galerkin (DG) spatial discretization is devised in order to obtain a discrete cell-centered Laplace operator. High order corner gradients of the velocity field are employed in 3D to derive the Laplace discretization, and the resulting viscous system is proven to be symmetric and positive definite. As such, it can be conveniently solved at the aid of the conjugate gradient method. Numerical results confirm the accuracy and the robustness of the novel schemes in the challenging stiff limit of the governing equations characterized by low Mach numbers
A high‐order parallel Eulerian‐Lagrangian algorithm for advection‐diffusion problems on unstructured meshes
No full textIn this paper, we present a high-order discontinuous Galerkin Eulerian-Lagrangian method for the solution of advection-diffusion problems on staggered unstructured meshes in two and three space dimensions. The particle trajectories are tracked backward in time by means of a high-order representation of the velocity field and a linear mapping from the physical to a reference system, hence obtaining a very simple and efficient strategy that permits to follow the Lagrangian trajectories throughout the computational domain. The use of an Eulerian-Lagrangian discretization increases the overall computational efficiency of the scheme because it is the only explicit method for the discretization of convective terms that admits large time steps without imposing a Courant-Friedrichs-Lewy–type stability condition. This property is fully exploited in this work by relying on a semi-implicit discretization of the incompressible Navier-Stokes equations, in which the pressure is discretized implicitly; thus, the sound speed does not play any role in the restriction of the maximum admissible time step. The resulting mild Courant-Friedrichs-Lewy stability condition, which is based only on the fluid velocity, is here overcome by the adoption of the Eulerian-Lagrangian method for the advection terms and an implicit scheme for the diffusive part of the governing equations. As a consequence, the novel algorithm is able to run simulation with a time step that is defined by the user, depending on the desired efficiency and time scale of the physical phenomena under consideration. Finally, a complete Message Passing Interface parallelization of the code is presented, showing that our approach can reach up to 96% of scaling efficiency
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