how to break text flow at book chapter breaks?

As it's open to interpretation what you are doing could make more sense to make one approach over another.

Perhaps if you can tell us a bit more what you're doing exactly?

So as pointed it out, it could be print book, or ebook.

So adding in Page Breaks or column breaks to the workflow would start you to a new page too.

You can use the Keep Options - 

Or compile the book using the book panel. 

But all the options have been discussed really. 

As long as your new chapter starts on a new page - the page numbering will continue.

For books that are printed it's favourable for chapters to start on a right hand page (or odd page).

But you don't have to do it this way - there's no 'rule' chapters need to start.

Break the text flow based on paragraph style. You will find a script for this task in the Communty Scripts.

I (and I think Eugene) read this as for print layout. His answer is what you need: assigning break options to a paragraph style (usually the chapter heading) in the Keep menu will give you any behavior you could want, including the common 'break to next right page.'

Your use of 'flow,' though, makes me wonder if you're working with an e-book. Getting page breaks in EPUB export is another and tricky process. Reflowable EPUB doesn't honor page breaks without some tweaking, especially to accommodate a range of readers.

Using a book file and using a different file for each chapter.

Failing that - a paragraph style for the chapter headings in the Keep Options