A manufacturing method is provided during which a body is additively manufactured. The body includes an engine case for a gas turbine engine, a support structure and an aperture. The support structure projects out from the engine case. The support structure includes a lattice, a wall and an internal volume. The wall surrounds the lattice. The internal volume is within the support structure along the lattice. The internal volume is filled with powder. The aperture is at an intersection between the engine case and the support structure. The powder is extracted from the internal volume through the aperture.

A bell mouth includes a circumferential wall, and a pressure changing component permeable portion arranged in the circumferential wall at a location where a separated distance from an axial fan is minimal. A fan unit includes the bell mouth, an axial fan, and a case that accommodates the axial fan and the bell mouth. The fan unit has an air layer between the circumferential wall of the bell mouth and the case.

A casing that is for a rotating machine and that is configured such that a plurality of housings are linked together, the casing comprising: a first housing including a first connection part that protrudes outward in a radial direction of the rotating machine and that has a first surface extending along the radial direction; a second housing including a second connection part that protrude outward in the radial direction and that has a second surface extending along the radial direction and being in contact with the first surface; and at least one fastening device that fastens the first connection part and the second connection part in the axial direction of the rotating machine, wherein at least one of the first surface or the second surface includes, at least at a portion thereof, a rough surface region having formed therein a plurality of laser irradiation marks formed by irradiation with laser light.