Fire Dynamics Simulator v3.0 was used to investigate and assess fire smoke transport and management in a realistic indoor sports center. An atrium fire test case illustrated the code's superiority over code-type empirical models for both accuracy and capability. Four fire scenarios in the Tsinghua University Sports Center were then simulated. The smoke layer's descent speed was predicted for each case. The importance of the door effect was revealed and an additional mechanical ventilation system for the building was proved to be of no help. The door effect must be carefully considered in future fire safety designs.