Each model update in the studio, also updates [application root]/.timestamp. When copying the new models to your server, make sure you also copy the .timestamp file.
The application's tomcat context file should include a parameter definition as follows:
One method to verify that configuration is correct, is to leave the application open in a browser window, update .timestamp, and switch focus back to the browser window which should perform a refresh.
If configuration is correct and you're still caching old models, make sure you're using browser defaults for caching, and if so, I guess we'll need a concrete example.
As for explicitly clearing the cache, try using Display Actions/Reload Application.
For best results, use the Firefox browser..