Hey,

i'm modelling flow past two parallel cylinder with different diameters and i'm unsure on what to set as the reference values for area and length, the model is 2D. For the single cylinder model i used the diameter which i believe to be correct. Please can somebody help me?

not that important! it does not effect the solution. get the solution, just set as to one of geometries, and then get necessary results (e.g. drag and drag coefficient) and then change it to another geometry and do the same! good luck