Abstract: A pericritical fluid system for a thermal management system associated with a turbine engine may include one or more sensors configured to generate sensor outputs corresponding to one or more phase properties of a pericritical fluid flowing through a cooling circuit of the thermal management system, and a controller configured to generate control commands configured to control one or more controllable components of the thermal management system based at least in part on the sensor outputs. The one or more sensors may include one or more phase detection sensors, such as an acoustic sensor.