How to remove index from memory ?

Hello
I am running a test to find the impact of corrupt indexes on queries. I corrupted the index file but observed that the queries continued to perform without issues. It was only on restart of the database that postgres realized that the indexes are corrupt and my queries started failing (with error like: ERROR:  invalid page header in block 0 of relation base/16384/16399)

My questions are:
1. How do I remove the indexes from memory ? I wish to stimulate the condition when indexes are no longer in database but the server has not restarted and see the effects of corrupt indexes.
2. Is there a more proactive and realtime way to detect corruption of indexes ?

Thanks for any inputs.