Abstract: The invention relates to a flow measuring device for measuring a parameter of a flow formed from a fluid which flows in a main direction of flow in a line, comprising a first line section for conducting the fluid out of the main direction of flow; a second line section for conducting the fluid back into the main direction of flow; a line connection section for connecting the first line section to the second line section; at least one ultrasound device for transmitting and/or receiving ultrasound waves; and an evaluation unit for carrying out a transit-time difference measurement and for determining the parameter, wherein at least one swirl generating unit for generating a swirl is provided which is arranged downstream of the first line section such that the generated swirl is directed in a direction which is opposite to a direction of a swirl present downstream of the first line section and upstream of the swirl generation unit.