Depends on what visa office will be processing your application.
Some offices send a letter confirming they have received your app (the AOR letter). Others don't. Those who do send it, can send it right away when they get your app or months later when they actually look at it.
You can check on e-cas to see when they've updated it to show they're processing it, but a lot of visa offices are rather slack about that so it might take a while for it to show up.
What is your visa office?