The article at the beginning defi nes multilayer and monolayer structure based on the structural characteristics of ship engine room. The smoke fi lling motions in multilayer and monolayer structures are studied by employing fi ltered balance equations and the Smagorinsky subgrid-scale model. The article investigates the distribution of smoke with iso-concentration and the height of smoke layer. The research indicates that the spread speed and the spread area of smoke in the
multilayer structure are greater than in the monolayer structure. The height variation of smoke layer is non-continuous in the multilayer structure and continuous in monolayer structure. The height of smoke layer decreased slowly within zone 1 in the multilayer structure, but the smoke fi lls the zone 1 more quickly in the monolayer structure. The examples demonstrate that the shortcomings of the structural hypothesis in traditional method badly affect the research results. The article suggests improvements for research of fi res in ship
