Sir, I think I have taken care of the dimensions from start till end. I will attach the images as well
I have given the domain dimension around 15000 X 12000 mm (Height X Width) and also the units are set to millimeters.
The close up view of truncated nozzle all dimensions are in millimeters.
Even in mesh settings I have ensure that units are in millimeters and the image below shows the global mesh settings where I changed parameters to
Global Element Size to 5mm
Transition to Slow
Smoothening to High
Number of CPU for parallel to 48 (I have also tried default number of CPU as well but there also it doesn't make any mesh it just shows 5% Meshing. )
Then I gave local face sizing of 1mm specifically for the jet region of the domain in order to ensure the cell area variation is not high across the jet region.
And the 1 message which you can see at bottom is not a warning or an issue because I stopped the meshing process after 1 day, I will attach that image as well. Which confirms that there is no issue of less memory available.