Please use the reciprocal value of hydraulic resistance, wich is called hydraulic conductance for the compatibility with other blocks and models!
Because zero hydraulic conductance means zero volumetric flow, it is much better to use this reciprocal value of hydraulic resistance.
Even it is not recommended, you can use this block, but do not forget to make reciprocal value (in example using Blocks.Math.Reciprocal) before connecting to library components!