The present disclosure is directed to a combustor assembly for a gas turbine engine. The combustor assembly includes an annular bulkhead adjacent to a diffuser cavity; a deflector downstream of the bulkhead and adjacent to a combustion chamber; a bulkhead support coupled to an upstream side of the deflector; a first walled enclosure coupled to the bulkhead support; and a second walled enclosure coupled to the first walled enclosure. The deflector and the bulkhead support together define a bulkhead conduit therethrough to the combustion chamber. The first walled enclosure defines a first cavity and a hot side orifice. The hot side orifice is adjacent to and in fluid communication with the bulkhead conduit. The second walled enclosure defines a second cavity and a second opening adjacent to a diffuser cavity.