PURPOSE: To uniform a pipe pressure by arranging a vortex amplifier in a flow line, and regulating a control flow to the vortex amplifier that is controlled by the output of a pressure detector arranged in a lower flow.

CONSTITUTION: A vortex amplifier 1 is arranged in a pipe line 2. The upper flow pipe 2 is connected to the radial mouthpiece 9, a lower flow pipe 3 is connected to the axial mouthpiece 10, and a control pipe line 4 is connected to a control mouthpiece 11 in line connection direction, of the vortex amplifier 1. A pressure transducer 7 is arranged in the lower pipe line 3, a pump 5 is controlled by the output of the pressure transducer, and the flow quantity passing through the control pipe line 4 is changed therewith. While the pressure of the lower pipe line 3 increases, the flow in the control pipe line 4 increases therewith, so the pressure drop generated by the vortex of the vortex amplifier 1 increases and the pressure of the lower pipe line 3 decreases therewith. By this manner, the pressure of the lower pipe line can be an uniform value.