A supercharged engine and operating methods thereof are described for adjusting an extent of fluidic coupling between separate channels of a two-channel turbine. In one particular example, a longitudinally displaceable flow transfer valve is arranged for movement lateral to the exhaust airflow that provides coupling between the channels, a position of the flow transfer valve within a flow transfer duct controlling the extent of fluidic coupling in addition to the rate of exhaust-gas flow through a blow-off line that conducts airflow past a rotor of the two-channel turbine. In this way, the flow transfer valve according to the present disclosure advantageously allows for adjusting a mode of supercharging based on one or more engine conditions to control the extent of fluidic coupling using a simplified valve arrangement.