Annulus contouring

An airfoil array segment for an airfoil array of a turbomachine, the airfoil array segment comprising:

• a platform having a platform surface and an upstream-side platform edge;
• at least two airfoils, whose leading and trailing edges define an inter-airfoil strip having an axial chord length on the platform surface;
• the platform surface of the inter-airfoil strip having a trough with a bottom, the trough being configured such that the bottom of the trough is a global minimum of the trough and a radial position of the trough decreases in the circumferential direction from a suction side of one of the at least two airfoils toward the pressure side of an adjacent other of the at least two airfoils relative to a reference surface toward the bottom of the trough and from there increases in a circumferential direction, at most up to a radial position of the reference surface, and a radial position of the trough decreasing axially in the downstream direction relative to a reference surface toward the bottom of the trough and from there increasing axially in the downstream direction, at most up to a radial position of the reference surface, and the platform surface of the inter-airfoil strip reaching at most a radial position of the reference surface, the reference surface corresponding to an uncontoured platform surface;
• wherein the global minimum is formed at an axial position of at least 40% and at most 60% relative to the axial chord length on the platform surface;
• wherein the trough begins at an axial position spaced upstream from the leading edge of the airfoil by at most 25% of the chord length of the airfoil at 50% of a radial span of the airfoil.