Surface-processed structure, surface-processed sheet, and propeller fan

A surface-processed structure comprising:

• a plurality of blocks, the plurality of blocks being three-dimensional objects arranged on a target surface, the target surface being a surface of a target object,
• wherein the target surface extends in a first direction and a second direction orthogonal to each other,
• the plurality of blocks is spaced apart from each other and is arranged side by side in the second direction,
• each of the plurality of blocks includes a top face including a plurality of grooves,
• the plurality of grooves is spaced apart from each other, is arranged side by side in the second direction, and extends from upstream to downstream in the first direction,
• a block clearance having a groove shape and extending in the first direction is formed between two blocks of the plurality of blocks, the two blocks being adjacent to each other in the second direction,
• a width of each of the plurality of grooves in the second direction is less than a width of the block clearance in the second direction,
• both end portions of the top face in the second direction are located above bottom portions of the plurality of grooves in a cross section of each of the plurality of blocks extending along a plane perpendicular to the first direction,
• an aspect ratio indicating a ratio of a depth to a width in the second direction of the block clearance gradually increases from the upstream to the downstream in the first direction,
• the aspect ratio of the block clearance at an upstream end portion is 0.5 or less, and
• the aspect ratio of the block clearance at a downstream end portion is 0.7 or more.