Compressor bleed air channels having a pattern of vortex generators

In one aspect, the present disclosure is directed a gas turbine engine including a compressor, a combustor, and a turbine in a serial flow arrangement. The compressor includes a casing having an inner wall and an outer wall. The inner wall defines a passageway for airflow through the compressor. The casing defines a bleed cavity between the inner wall and the outer wall. The inner wall has an opening. The casing defining a channel between the opening and the bleed cavity to direct airflow into the bleed cavity. The channel is defined by a first wall and a second wall of the casing. The second wall being downstream of the first wall. A surface of the first wall has a pattern to reduce flow separation in the channel.