outer and inner periphery fig2 a and b show the control device 2 in larger scale the device consists of a first disc shaped housing body 4 with an outer cylindrical segment 5 and inner cylindrical segment 6 and with a central hole or aperture 10 and a second disc shaped holder body 7 with an outer cylindrical segment 8 as well as a preferably flat disc or freely movable body 9 provided in an open space 14 formed between the first 4 and second 7 disc shaped housing and holder bodies the body 9 may for particular applications and adjustments depart from the flat shape and have a partly conical or semicircular shape for instance towards the aperture 10 as can be seen from the figure the cylindrical segment 8 of the second disc shaped holder body 7 fits within and protrudes in the opposite direction of the outer cylindrical segment 5 of the first disc shaped housing body 4 thereby forming a flow path as shown by the arrows 11 where the fluid enters the control device through the central hole or aperture inlet 10 and flows towards and radially along the disc 9 before flowing through the annular opening 12 formed between the cylindrical segments 8 and 6 and further out through the annular opening 13 formed between the cylindrical segments 8 and 5 the two disc shaped housing and holder bodies 4 7 are.