Internal structure of a primary exhaust duct having a separator of which the geometry varies depending on the temperature

An internal structure of a primary exhaust duct of a turbomachine, said internal structure comprising:

• a primary wall comprising a surface of revolution about a longitudinal axis, allowing air to pass through orifices and forming an internal surface of the primary exhaust duct,
• an interior skin comprising a surface of revolution about the longitudinal axis, arranged inside the primary wall, and
• at least one separator which is attached only to the interior skin by a region along a first edge by at least two attachments and which has a first geometry and a second geometry,
• wherein a change from the first geometry to the second geometry takes place when a temperature of the separator exceeds a first temperature, and a change from the second geometry to the first geometry takes place when the temperature of the separator drops below a second temperature less than or equal to the first temperature, and
• wherein a coefficient of expansion of the separator is greater than that of the interior skin,
• wherein, in the first geometry, the separator is wound on itself, and
• wherein, in the second geometry, the separator is opened out and extends so as to bring a second edge as close as possible to the primary wall.