This disclosure includes various embodiments of apparatuses for encapsulating and stopping a flowing mass of fluid (e.g., liquid such as water, or gas such as air) to extract the kinetic energy from the mass, and for exhausting the mass once stopped (spent mass, from which kinetic energy has been extracted). This disclosure also includes various embodiments of systems comprising a plurality of the present apparatuses coupled together and/or one or more of the present apparatuses in combination with one or more flow resistance modifiers (FRMs). This disclosure also includes various embodiments of methods of extracting kinetic energy from a flowing mass of fluid (e.g., liquid such as water, or gas such as air) by stopping the mass, and for exhausting the mass once stopped (spent mass, from which kinetic energy has been extracted). This disclosure also includes embodiments of mechanical energy-storage or accumulation devices.