Hello,
"how to define such initial conditions, that the first part of geometry has pressure of 8 bar and the remaining two parts have 1 bar"
You can patch different cell zones with the initial pressure values. Check this section of the user's guide for more info: 32.9.2. Patching Values in Selected Cells (ansys.com)
"how to define that the whole boundary consist of stochiometric mixture of hydrogen and air."
I didn't get this. Can you please elaborate?
"how to import combustion mechanism for detonation of hydrogen-air mixture"
For this, you may want to check this: 44.1.54. File/Import/CHEMKIN Mechanism... (ansys.com)
If you are not able to access the links, please refer to this forum discussion: How to access the ANSYS Online Help
Thanks!
Nikhil