Question: i have added a splash screen to my application by adding Default.png.
the splash screen works fine in the simulator but not showing on real device

Answer: 
The file name must be Default.png (with a capital D). Also, do a clean/rebuild of the entire project to ensure the most recent version of the file is being included in the project.
Make a "Default.png" file (with a capital "D"). Then clean all targets and build again.