A cleaner head for a vacuum cleaner comprising a casing. The casing comprising a primary inlet through which a dirt-laden fluid is drawn into the cleaner head, a secondary inlet through which an ancillary fluid is drawn into the cleaner head, and an outlet through which the dirt-laden fluid and the ancillary fluid are discharged. The cleaner head also comprising a brushbar housed within the casing and a turbine assembly housed within the brushbar. The brushbar is mounted to the casing at a first end by a first bearing retained in a first bearing mount and at a second end by a second bearing retained in a second bearing mount, and the ancillary fluid is drawn through the brushbar from the first end to the second end and drives the turbine assembly. At least one of the first or second bearing mounts has a castellated surface such that a fraction of the dirt-laden fluid forms a diverted fluid that is drawn through the castellation and into the brushbar.