To provide a fluid diode having sufficiently large differences in flow resistance by the single use of a vortex chamber by increasing the energy loss of a reverse direction flow.
The fluid diode 1, which has flow resistances different depending on the flow direction of a fluid, comprises a vortex chamber 4 into which the fluid is introduced, an inlet-side flow path 5 displaced relative to the width direction center C of the vortex chamber 4 to one side and allowed to communicate with the vortex chamber 4, an outlet-side flow path 6 displaced relative to the width direction center C of the vortex chamber 4 to other side and extending in an opposite direction to the inlet-side flow path 5 to communicate with the vortex chamber 4 and a projection portion 7 provided in the connection portion between the vortex chamber 4 and the inlet-side flow path 5 to generate a vortex flow A2 in the vortex chamber 4 when the fluid is flowed from the outlet-side flow path 6 into the vortex chamber 4. The projection portion 7 is formed so that the curvature radius R of a guide surface 8 facing to the width direction center C of the vortex chamber 4 gets smaller from the base end 7a of the projection portion 7 toward the leading end 7a thereof to direct the vortex flow A2 generated by the projection portion 7 to flow into the outlet-side flow path 6.
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