Sir, I got what you are trying to say, the surface area of the leaf shaped split part of domain alone is 1.93 e^8 mm2 and if I give face meshing of 1mm then it will be approx 193 million cells for hex type mesh. It was a great insight that I was blindly giving the local sizing dimension.
I understand now it very clearly that it is a huge number.
Even If I give 2mm face sizing then for leaf part alone it will be close to 48 million cells.
So I think I should give face sizing of 3mm as it will lead to 21 million cells and also considering the whole domain, the total cells should be less than 63 millions as outside leaf shaped part, local sizing is of 5mm.
So if I go with 63 million cells it should take around 1hour or at most 4 hours considering that one your intern student is able to create 20 million cells mesh in 20-40 minutes.
Ok Sir, I will try that hoping for the best.