Automatically append search query?

Hi! I’m using Search Unleashed, which I’ve discovered ignores WP’s default search syntax. Adding &cat=1 to the end of a query does not, in fact, search only posts from that category. Adding the ?s= search query to the end of the category URL does not work, either.

I have discovered, however, that adding the name of the category to the search query sort of works.

So, I’m wondering if there might be a way to automatically append every search query from one of my search forms to include two additional words (the two-word category name). So my queries would look like this:

myurl.com/?s=search+query+category+name

I tried adding a second text input box in the search form to do this, but that gave me a query that looked like this:

myurl.com/?s=search+query&s=category+name

…which broke on the second page (reverted to only the category name).

Please chime in if you have any ideas. Thank you!