Study On The Simulation Scheme Of Multiscale Modeling In The Field Of Urban Tunnel Fire

With the rapid development of economy, crowded city traffic will encountergreater demand. In order to make urban transport play an effective role in the economic,the development of urban underground traffic must become a trend. In addition to theunderground subway traffic and long straight tunnel which has been widely used, thenew type underground tunnels such as urban underground circular tunnels come in ourlives. And they also come with a complex series of fire hazards.Fire research methods commonly used are software simulation and experimentalmodeling. For cases in which the station is difficult to produce an experimental model,software simulation is the main research tool. There are three kinds of softwaresimulation model, namely the network mode, the regional model and field model. Fieldmodel is the most common used model, which can predict the global field of fire withina reasonable margin of error. But over90%predecessors are concerned about refluxoccurred while ignoring the operation and effectiveness of the entire exhaust system. Infact, in most cases the boundary conditions are rough estimates or got from the coldsmoke experiment, which can’t be the basis for the evaluation of the whole system. Sofor such a large-scale urban underground tunnel with complex systems, field modelingstudy can’t achieve a good simulation accuracy, we can’t assess the operation of theoverall system. Therefore, the multi-scale simulation program is a possible fire researchmethod to study city underground tunnels.Flow field near the fire source exists complex three-dimensional mixing flow withlarge change of temperature and speed. So the region can only be researched by thefield model. However, at some distance away from the fire or away from the fan, theflow field layer becomes apparent one-dimensional flow pattern. One-dimensionalnetwork model can be used here. And also1D model can provide boundary conditionsto field model, and they two together can assess the overall system solution.In this paper, the interface for data exchange between two different models and theaccuracy of field model are the main research problems. Because involving theexchange of data between models, field models require a higher accuracy of the results.This paper will mainly verify by comparing the different grids and determine theappropriate near field in the multi-scale simulation model. This article will determinethe position of the interface between the different models based on the fully developedflow field characteristics. And the multi-scale prediction software would beprogramming based on the above findings. With the data of the tunnel input, theprogram can automatically generate the suitable simulation method of the tunnel. This paper identified that the accuracy suitable for multi-scale simulation modelis higher than that needed for the traditional simulation and also clearly determined theinterface of long straight tunnel, curved tunnel and fork tunnel. Two versions of themulti-scale prediction software TSAS have also been developed. They can be used asresearch basis of underground urban tunnel simulation.