A method for assembling a gas turbine combustor includes providing a combustor case having a first end, a second end, and a centerline extending there between, coupling an end cover to the case first end, coupling a combustor liner within the case such that the liner is substantially coaxially aligned with respect to the case, and providing a streamline flow conditioner including a body that includes a radially outer surface and a radially inner surface, a deflection plate that extends from the body, and coupling the streamline flow conditioner to the case second end such that the streamline flow conditioner is coupled radially between the case and the combustor liner such that the deflection plate is adjacent the case second end. The deflection plate inner surface at least one of extends radially outward with respect to the centerline and defines a plurality of openings within the plate inner surface.