Numerical and experimental study of atrium enclosure fires in a full scale fire test facility. Póster

For the present work, a 3-D numerical model has been implemented to simulate the thermal and fluid fields induced by an enclosure fire in an atrium and for smoke exhaust system assessment. This study is focused on the ‘Fire Atrium’, a new full-scale fire test facility of the Technological Metal Centre in Murcia, Spain. It is an aluminium prismatic squared base building of 19.5 m x 19.5 m x 20 m with several vents arranged in its walls and four exhaust fans at the roof

Influence of different make-up air configurations on the fire-induced conditions in an atrium

This paper provides with a set of full-scale experimental data of atrium fires. These data could be used as benchmarks for future numerical validation studies. In particular, the influence of the make-up air velocity as well as the position and area of the vents in an atrium is assessed both experimentally and numerically. Experimentally, the effect of different make-up air supply positions and inlet area on the fire-induced inner conditions and smoke layer descent was studied by means of three full-scale fire tests conducted in a 20 m cubic atrium. Detailed transient measurements of gas and wall temperatures, as well as pressure drop through the exhaust fans and airflow at the inlets were recorded. Later computational fluid dynamics (CFD) simulations of these tests were performed with the code Fire Dynamics Simulator (FDS). Experimentally, the lack of symmetry in make-up air vents and the large inlet area turn the flame and plume into more sensitive to outer effects. However, no significant difference has been observed between the make-up air topologies assessed. Even make-up velocities higher than 1 m/s, with symmetric venting topology, have not induced important flame or plume perturbations. Numerically, the simulations agree well with the experiments for the cases with make-up air velocities lower than 1 m/s. Poor agreement has been found for the case with inlet velocities higher than 1 m/s

Low and medium power full-scale atrium fire tests and numerical validation of FDS

The inclusion of atria within modern large buildings is relative recent. These structures are important architectonical features since the 60’s. Atria are a source of discussion within the fire science community. They introduce complex designs and non conventional architectonical elements that can lead to fire environments diverging from those in current codes. Because of this, the current trend in fire safety in atria is towards performance based design. At this point, it is still necessary to improve and validate the existing numerical models. For this aim, some tests were carried out at the Murcia Fire Facility. These consist of 19 full-scale fire tests that provide with new experimental data of atrium fires. The fire size, the smoke extraction rate and make-up openings size and location were varied. At the present paper, a set of results from some of these experiments in a 20 m cubic facility are reported and discussed. Additionally, comparisons with the predicted results from Fire Dynamics Simulator (FDS) v.4 are also presented. FDS has turned out to be capable to predict the transient fire-induced conditions inside the facility accurately, above all at the upper parts. The predicted smoke layer descent has been also compared with the experimental one with good agreement.The authors want to acknowledge the Centro Tecnológico del Metal of Murcia for the use of their test rig, the Professor J. L. Torero, T. Steinhaus, C.Abecassis-Empis, P. Reszka, W. Jahn, from the University of Edinburgh, for their technical suggestions and supervision. Simulations have been carried out at the computational facilities of the Technological Research Services of the Technical University of Cartagena (SAIT) and the University of Jaen. This work has been supported by Ministerio de Educación y Ciencia of Spain (Projects CT/G30572473, and FIT-020700-2004-25 and grant TRA2006-15015) and by the Junta de Andalucía of Spain (Project number P07-TEP-02693)

Floquet stability analysis of a two-layer oscillatory flow near a flexible wall

We investigate the linear Floquet stability of two fluid layers undergoing oscillations in the direction parallel to the flexible wall that separates them. This canonical configuration is inspired by the cerebrospinal fluid flow in the spinal canal of subjects with hydro-/syringomyelia.The analysis focuses on the marginal conditions for the onset of instability, and how these depend on the spatial wavelength of the perturbation, and on the values of the control parameters, which are the two channel widths, the Reynolds number, and the wall stiffness. Unstable perturbations are found to oscillate synchronous with the base flow. The wavelength of the most unstable perturbation, of the order of the stroke length of the basic oscillatory motion, depends strongly on the wall stiffness, but is only weakly influenced by the channel widths and the Reynolds number. In general, around criticality, it was found that increasing the Reynolds number has a destabilizing effect, and that decreasing the canal widths stabilizes the instability. The wall stiffness on the other hand has a non-monotonic effect, exhibiting an intermediate value for which the instability is maximally amplified. The present analysis is a first step towards a better understanding of the physical mechanisms that govern many (bio)fluid mechanical problems that involve oscillatory flows near compliant walls

On the Fluid Dynamics of the Make-Up Inlet Air and the Prediction of Anomalous Fire Dynamics in a Large-Scale Facility

The present paper is focused on the fluid dynamics of the make-up air at the vents in case of an atrium fire, its influence on the fire-induced conditions and the necessity of properly model it to obtain an accurate numerical prediction. For this aim, experimental data from two full-scale atrium fire tests conducted in a 20 m cubic facility, with venting conditions involving mechanical smoke exhaust and make-up air velocities larger than 1 m/s, and with different fire powers, are presented. Subsequent numerical simulations of these tests have been performed with the code Fire Dynamics Simulator v5.5.3. Two different approaches have been followed to simulate the make-up air inlet fluid dynamics, involving one domain which only considers the inside of the building and another which includes part of the outside. In the former simulations, anomalous phenomena around the fire appear, while the inclusion of the exterior domain provides with a completely different fluid dynamics inside the facility which agrees better with the experimental data. A detailed analysis of the fluid mechanics at the air inlet vents is conducted to explain these discrepancies. Finally, further simulations are performed varying the make-up area to assess the appearance of the aforementioned phenomenon.This research was supported by the Spanish MCyT and Junta de Andalucia under Projects # DPI2008-06624-C03-02 and # P07-TEP02693, respectively. CGM wants to acknowledge the research stay grants IAC-2010-3 and A-13-2010 from the Junta de Andalucia and the University of Jaén, respectivel

Cavity flow induced by a flexible membrane in an oscillatory channel flow: case study of syringomyelia.

In this work, we study the flow inside a Syringomyelia, modelled by a cavity separated from a channel with an elastic membrane. The oscillatory flow of the channel is transmitted to the cavity through the deformation of the membrane. We study the structure of the time-dependent and stationary flow induced inside the cavity and the deformation of the membrane under different problem conditions.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Is adenosine deaminase (ADA) activity in saliva and serum a more accurate disease detection tool than traditional redox balance parameters in early-lactating dairy cows?

Enzyme adenosine deaminase (ADA) is a marker of inflammation in domestic animals, but it is unclear whether it is a reliable marker of oxidative stress, especially in the transition period in dairy cows. This study aims to assess if ADA and redox status measurements in saliva provide the same utility to detect disease condition as that obtained from serum. Sixty-eight multiparous Holstein cows, between 2 and 3 weeks postpartum were selected. Five study groups were established: control (healthy), and cows with ketosis, mastitis, laminitis, and metritis. The parameters measured were ADA activity, total oxidants (TOS), antioxidants (TAC), and OSi ratio. Regarding redox status, no significant differences arise in both saliva and serum being the correlations negative and not significant. In saliva, ADA activity in healthy cows differs from those with pathological processes, having the lowest activities. In serum, ADA activity is similar in the healthy and ketosis cows, showing the lowest activities meanwhile animals with mastitis, laminitis, or metritis have significantly higher activities. In conclusion, the measurement of ADA activities and redox status in saliva does not give consistent results, being preferable to measure them in serum during the transition periodOpen Access funding provided thanks to the CRUE-CSIC agreement with Springer NatureS

Estudio numérico experimental de un incendio controlado en una nave industrial. Póster

Se ha desarrollado un modelo numérico para la simulación de los campos fluido y térmico que genera un incendio en el interior de una nave industrial. La nave es la Nave del Fuego del Centro Tecnológico del Metal (Alcantarilla, Murcia). Esta nave tiene unas dimensiones de 19,5 x 19,5 x 17,5 m con un techo piramidal de altura 2,5 m. Consta de cuatro extractores de ventilación en la parte superior del techo y una serie de rejillas de ventilación en la parte inferior de las paredes. El fuego se sitúa en el centro del suelo de la nave. Para este trabajo se ha realizado una parte experimental y una numérica. Se han realizado ensayos experimentales con diferentes potencias de fuego y topologías de ensayo. Se han realizado simulaciones numéricas estacionarias y transitorias. En este trabajo se realiza la comparación de los resultados obtenidos numéricamente con los medidos durante un ensayo experimental realizado, con características similares

Experiments and FDS simulations on the make-up air influence on low-power fires within an atrium

This paper aims to study the influence of different make-up air configurations on the inner conditions induced by low-power fires within an atrium. For this objective, three full scale fire tests in a 19.5 m x 19.5 m x 19.5 m facility have been conducted. In these tests, symmetric and non-symmetric make-up air configurations, as well as different air inlet areas have been assessed. Later FDSv4 simulations of the tests have been performed and comparisons between measurement and predictions are reported. Experimentally, no significant difference has been observed between the make-up air topologies assessed. Even make-up velocities higher than 1 m/s, with symmetric venting topology, have not induced important flame or plume perturbations. Numerically, the simulations agree well with the experiments for the cases with make-up air velocities lower than 1 m/s. Poor agreement has been found for the case with inlet velocities higher than 1 m/s

Simulation of the smoke layer interface height for a fire induced in a atrium

The calculation of the smoke layer interface height in case a fire breaks out in an atrium is determinant to make an appropriate fire safety system design. Most of the expressions used to calculate it assume no mass flow through the smoke layer interface. With this object a numerical model that simulate fire-induced thermal and fluid fields in an atrium using the finite volumes procedure code FLUENT has been developed. The model has been validated from new full-scale fire experimental tests performed at the ‘Fire Atrium’ of the Technological Metal Centre, Murcia, Spain. At the present work the experimental data from one fire experiment are shown. In this experiment an heptane pool fire placed at the centre of the floor was used, releasing an average heat of 1.8 MW. A comparison between one empirical expression commonly used and an experimental temperature criterion, both for computing the smoke layer interface height, with the one predicted by the model is performed. The model agrees better with the second one and shows a mass of air across the smoke layer interface should be taken into account