Abstract: The present disclosure is directed to a combustor assembly for a gas turbine engine comprising a fuel nozzle and an annular shroud. The fuel nozzle comprises a centerbody extended along a lengthwise direction. The fuel nozzle defines a nozzle centerline extended through the centerbody of the fuel nozzle along the lengthwise direction. The fuel nozzle defines a plurality of exit openings in circumferential arrangement on the centerbody relative to the nozzle centerline. The annular shroud surrounds the centerbody of the fuel nozzle. At least a portion of the shroud defines a contoured structure defining a waveform.