I don't know HOW you're saying hi. If someone clearly doesn't want to talk to you, the best thing is to walk briskly past them saying 'Hi!' as you pass but without pausing or trying to catch their eye.
In the evening reverse the process, saying 'Bye', maybe add 'See you tomorrow', but again, don't pause, don't catch their eye.
This way YOU are still polite but with the absolute minimum effort.