If you’re new varnish user, this is some words about varnish:

Varnish is an HTTP accelerator designed for content-heavy dynamic web sites. Unlike other HTTP accelerators, such as squid, which began as a cache on the client, or Apache2, which is mainly an origin server, Varnish was designed from the ground up as an HTTP accelerator..

Now I will show you how to purge all the cache without restarting the daemon.
The following coomand will do this for you:

varnishadm -T 127.0.0.1:6082 url.purge .

Enjoy