Abstract: Torsional vibration damper which is suitable for dampening the motion of a rotatable element, said torsional vibration damper comprising an ‘actuation’ element which is connectable to the rotatable element, an ‘inertia’ element arranged co-axially and rotatably with said actuation element, an enclosed volume between said inertia element and said actuation element where a cross section through said enclosed volume taken on a plane which is parallel to the axis of the actuation element comprises at least one ‘axial’ portion which is arranged essentially parallel to the axis of the actuation element, an Electro-Rheological or a Magneto-Rheological fluid arranged at least in a part of said enclosed volume, and an electric or a magnetic field generator in the form of a coil which generates an electric or a magnetic field which passes through at least a portion of said enclosed volume.