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Ventilation is essential to provide a smoke-free path for safe passenger evacuation and effective rescue services in case of a tunnel fire. The critical ventilation velocity, VC, is defined as the minimum velocity which creates this safe passage by preventing smoke from spreading upstream in tunnels. This research discusses smoke flow control in tunnels with a focus on the important parameters affecting critical velocity. Critical velocity values are evaluated for different heat release rates and results show good compliance with model-scale experiments. The study is extended to investigate effects of fire source blockage ratio and lateral location, tunnel slope and ventilation air relative humidity on the behavior of critical velocity. Results show a drop in VC about equal to blockage ratio occurs in presence of fire source blockage. Investigation of critical velocity in sloped tunnels illustrates that for each %1 increment in negative slope, 2.5% higher ventilation is required. Results also show that air relative humidity does not have significant effect. However, fire lateral location impacts critical ventilation velocity in such a way that about 10-20% higher airflow is necessary to suppress smoke in a near-wall fire in comparison with a middle-tunnel fire.

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Fire spread from one body to another in a road tunnel is investigated in this study, with respect to the phenomena and the physical concept. Fire Dynamics Simulator will be used as a CFD tool. Two wood boxes representing cars are modeled in a 40m long tunnel with longitudinal ventilation and fire transmission from one to another is considered. Ignition temperature is assigned to the second box surface as the ignition start condition. Indeed, ignition start of the second box depends on its temperature rise to a certain value that is extracted from experimental data. At each case, ignition time of the second box is captured. Furthermore, fire spread phenomena is considered quantitatively and qualitatively. The results show that increase of ventilation velocity causes a first increment and then decrease in ignition time, due to both cooling and smoke plume inclination effects. Also with increasing the distance, ignition time increment rate is faster at low HRRs. In addition, the results show that the tunnel height reduction has stronger effect on ignition time for lower HRRs. Finally, because of forced ventilation dominance in high ventilation velocities, no noticeable influence on ignition time is observed by changing the tunnel slope. To confirm accuracy of the numerical model, a validation with experiments will be presented too.

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Development of wave energy convertors (WEC) is one of the main challenges that naval architectures have encountered, recently. One of the most important approaches before construction of WECs is the evaluation of their conceptual models in computational fluid dynamics (CFD) software. Therefore, in the current article, an innovative model of wave energy convertor is presented and hydrodynamic performance of proposed model in Persian Gulf has been examined. For accurate simulation of dynamics of WEC, mesh morphing technique is utilized. Since the presented WEC is an innovative design and there is no experimental result for validation purpose, it is tried to verify the numerical setup using similar experimental problems which have the various characteristics of the considered problem. Then, several different geometries including flat and foil pedals, and big and small semi-spherical pedals as a part of WEC have been analyzed, numerically. Small semi-spherical pedal has been determined as the best possible geometry. Number of pedals has been another parameter which has been studied and eight pedals model has been recognized as optimum choice. Finally, optimum WEC has been simulated in nine different waves and the results have been presented.