Oh gosh, I'm currently in total panic! I can't think properly anymore, my heart has been racing for hours now. Yesterday I was informed that I've been selected for a PhD. I was in complete bliss all day. Then at night I realised that my fairly easy life might be over and that I'll have to work really hard for this. And today I'm in panic and can't calm down.

This project will involve some modeling, partly using exisiting software, partly adjusting those, partly existing code and partly adjusting it. The background for this (fluid flow modeling in space) consists of many integrations, and quite honestly, I understand nothing of this. I'm only just learning to programme as well. I know I will have to learn a lot for this, but will I be able to do so, and to understand it? Am I supposed to understand this now even before I start?

Help!

Did you have similar concerns before you started? How did you deal with it and how did it turn out in the end? Am I expecting too much at this pre-project stage?

Our backgrounds are very similar and yes your fears are justified to a great extent. This PhD will probably rule your life for the next few years. Relatively few attempt it but it is that challenge which attracts most of us.
You won't know everything at the start and nobody will expect you to. What you will be expected to do is break down the stuff you want to learn about and get started on your reading and playing around with the tools and things like that. If you are lucky enough to have a break before sarting then use it to read papers and start learning the required maths and programming etc. The sooner you start the better. I started full time learning maths and things like that about 4 months before I began the PhD. Even then it took me four to five months before I could come into the office without feeling like a fraud.
There probably won't be a PhD student that you meet who is truly confident that they are on top of things: beware of those faking it.

The PhD is probably the hardest thing you'll ever do. Buckle up and enjoy the ride.
This will stretch you emotionally to your breaking point. My advice would be to avoid negative people and those whose constant low moods wear out your resilience. You need to find ways to keep your spirits as high as possible because there will be many times when you will want to quit. Some of those times might last months and months.
Good luck.

Hey roundthingy! You're most likely good enough to do a PhD since you've been selected! Congratulations! One of the most helpful things I read about doing a PhD prior to starting was that it was less about intelligence (let's face you - you have a good enough level of that otherwise you wouldn't have made it this far) and more about things like patience, resilience, and blimmin' hard work (perseverance). Of course you're good enough!

You could do some prep, as pm133 suggests, if you are motivated to at this stage. But if not, I would just use it as a chance to give yourself a rest before starting. Also, once you start, it can feel a bit like you're completely lost for a good few months (nearly the first year for me) because of the lack of structure, expectations not clear etc. But it gets better : )

Hope this helps!