An aspirator includes a duct having a wall with a surface bounding a converging portion and a diverging portion of the duct. The converging portion of the duct has an inlet and the diverging portion of the duct has an outlet, the inlet being in fluid communication with the outlet through the converging portion and the diverging portion of the duct. The surface of the duct wall includes a conformal surface portion extending between the inlet of the duct and the outlet of the duct that is conformal with an aspirator seat surface portion of a support structure to conform the duct to the support structure. Evacuation assemblies are also described.