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: 
Check the case of the file name.

Default.png, default.png, Default.PNG and DEFAULT.png are all different files on the device, but not in the simulator.
Sometimes this issue hapens, when .png file was renamed from .jpg file. 
So, for example, you had image.jpg, you've renamed in to image.png, and using this image.png. It'll be correctly displayed in simulator, and won't work on device