In this work, we utilize stochastic geometry to investigate the performance of mobile unmanned aerial vehicle (UAV) networks providing ground coverage service in post-disaster scenarios or coverage blind areas. The location of ground users is modeled as a Poisson cluster process (PCP) to represent the distribution clustering of ground users in these scenarios, i.e., node clusters in internet of things (IoT). A flying UAV serving as aerial base station (ABS) is forced to move around a cluster center with circular trajectory to provide information coverage service for that user cluster. By considering the periodic fluctuation of network topology caused by the movement of UAVs, we derive the success probability (SP) with Type-I hybrid automatic repeat request (HARQ) retransmission scheme. The simulation results verify the correctness of theoretical results and demonstrate the effect of key parameters on transmission performance.