Analysis of flow structure of tunnel fire based on modal decomposition

Abstract

In order to study the large scale flow structure of fire smoke in tunnels, this paper uses the excellent ability of proper orthogonal decomposition for the first time to extract flow field structure, processes the flow field data obtained from numerical simulation, obtains the 2-D and 3-D large-scale flow structure of fire smoke in tunnels and analyzes it. The proper orthogonal decomposition of temperature and velocity pulsation field shows that the proportion of first-order modal energy in temperature field is much higher than that in velocity field, indicating that the flow structure of velocity field is more complex than that of temperature field. Through modal phase analysis and modal decomposition of 3-D flow field, the influence of mode on fire smoke flow is recognized, and the understanding of tunnel fire smoke flow structure is deepened. The low-order mode is closely related to smoke flow. The increase of fire power has little effect on the reconstruction of flow field, and the cross-section energy recovery ratio near the fire source is higher under the same fire power.