Abstract: A sensor apparatus includes a cylindrical sensor window defining an axis, and a plurality of at least three tubular segments fixed relative to the sensor window. Each tubular segment is elongated circumferentially relative to the axis. The tubular segments collectively form a ring substantially centered around the axis. Each tubular segment includes at least one first nozzle and at least one second nozzle. The first nozzles and second nozzles are arranged in an alternating pattern around the ring. The first nozzles each have a direction of discharge in a radially inward and axial direction forming a first angle with the axis, and the second nozzles each have a direction of discharge in a radially inward and axial direction forming a second angle with the axis, the second angle being different than the first angle.