Fluid Cavity Abaqus

Hi,

My model is made of 3 different layers. The interaction between these 3 layers is define through cohesive surface behaviour and between the first 2 layers a small crack is defined. Now I am trying to define fluid into this cavity and see how applying fluid pressure the crack propagates. I am facing problems during the definition of the fluid cavity regarding the position of the reference node. Attached the input file.