Embodiments are generally provided of a gas turbine engine including a rotor assembly comprising a shaft extended along a longitudinal direction, in which a compressor rotor and a turbine rotor are each coupled to the shaft; a casing surrounding the rotor assembly, in which the casing defines a first opening radially outward of the compressor rotor, the turbine rotor, or both, and a second opening radially outward of the compressor rotor, the turbine rotor, or both; a first manifold assembly coupled to the casing at the first opening; a second manifold assembly coupled to the casing at the second opening, in which the first manifold, the casing, and the second manifold together define a thermal circuit in thermal communication with the rotor assembly; and a fluid flow device in fluid communication with the first manifold assembly, in which the fluid flow device provides a flow of fluid to the first manifold assembly and through the thermal circuit, and further wherein the flow of fluid egresses the thermal circuit at the second manifold assembly.