A turbomachine includes a compressor section, a combustor operatively connected to the compressor section, an end cover mounted to the combustor, and an injection nozzle assembly operatively connected to the combustor. The injection nozzle assembly includes a plurality of mixing tube elements. Each of the plurality of mixing tube elements includes a conduit having a first fluid inlet, a second fluid inlet arranged downstream from the first fluid inlet, a discharge end arranged downstream from the first and second fluid inlets, and a vortex generator arranged between the first and second fluid inlets. The vortex generator is configured and disposed to create multiple vortices within the conduit to mix first and second fluids passing through each of the plurality of mixing tube elements.