An apparatus for determining fluid flow in a pipe includes an ultrasonic flowmeter which communicates with the interior of the pipe through at least one pair of apertures, where each aperture of the one pair of apertures has an effective diameter. The apparatus includes a turbulence conditioner disposed in the pipe having openings where the pitch between openings is a function of the effective diameter of the aperture. A turbulence conditioner for a pipe has openings and a pitch. The conditioner has walls between the openings whose thickness is a function of the pitch. The conditioner has a length which is a function of the pitch. A method for determining fluid flow in a pipe includes the steps of flowing fluid through a turbulence conditioner disposed in the pipe having openings where the pitch between openings, is made a function of an effective diameter of an aperture of an ultrasonic flowmeter which communicates with the interior of the pipe through the aperture. There is the step of measuring the flow with the meter. A method for producing a turbulence conditioner.