Why do we need nondimensionalization in CFD? Is there any advantage?

Thanks in advance.

for YOUR specific problem you don t necessarily need to make your equation dimensionless. It is interesting however to make it dimensionless, because for example let's say you wrote a code for a big plane, your company will never pay a prototype to verify your code is correct. However they might build a lil prototype with smaller dimension. The results if they have not been render dimensionless won't be the same. However, if yopu make the equation without dimension, then you can compare the dimensionless results. Or, if someone wants to compare his results with yours (he might not have the same geometry as yours), if both your results are dimensionless, then they can be compared together. I hope that helps.

Non-dimensionalization reduces the number of variables as well as it gives the generalized results for the particular problem.

I prefer dealing with dimensional set of equations. It gives you a sense of the size of the problem. Once i attended a talk in which a student was solving a non-dimensional set of equations. At the end I asked him , "what is the diameter of your pipe?" and his answer was "It is non-dimensional!" On a more serious note, at least for me, working with dimensional equations just feels better.

non-dimensionalisation often helps you in understanding the physics underlying because all one has to understand is the effect of say diffusion/convection (Re), or say idea about heat flux at boundary (Nu), etc. however for all problems it may not be possible to go for non-dim at all, e.g often in phase change problems like melting/solidification.