Yes, you can flush the data buffer like this (but seriously, don't!):
DBCC DROPCLEANBUFFERS
Use DBCC DROPCLEANBUFFERS to test queries with a cold buffer cache without shutting down and restarting the server.
To drop clean buffers from the buffer pool, first use CHECKPOINT to produce a cold buffer cache. This forces all dirty pages for the current database to be written to disk and cleans the buffers. After you do this, you can issue DBCC DROPCLEANBUFFERS command to remove all buffers from the buffer pool.
You have already ruled out the database as your bottleneck (which it is often), so rather than freeing the data buffer cache, I suggest you profile your code.