Dear Dr. Ning,

As you can see from the review reports, one reviewer (reviewer 2) is generally positive with a lot of specific comments for improvement, while the other reviewer (reviewer 1) has some more serious concerns, in particular with respect to the perceived statements on effectiveness of paired VAWTs

Regarding the comments of reviewer 2, please take them carefully into account – the approach that you suggested in your reply is alright for that. When you submit a new version, make sure to provide per reviewer and per comment a final list of changes that originated from that comment.

Reviewer 1 expressed specific concerns related to your conclusions with respect to effective power gains of closely spaced turbines, and the statement that advantageous effects are unlikely. There are two approaches to this. You can either stick to your claims, but in that case, you should significantly upgrade the validation of your model, etc. as also requested by the reviewer. If you choose this approach, I will most probably send the paper back to the reviewers for a second round of review (thus ‘major review’). A second approach, as you already partly suggested in your response to reviewer 1, is to tune down some of your claims and limit the focus of your paper explicitly on the development of a (linear) version of actuator cylinder theory. However, in that case, please make sure that you properly remove, tune down (and properly discuss) any (remaining) statements on effective gains of paired VAWTs. For instance, the second paragraph of the abstract is out of place in that case, as you cannot make any decisive statements on mutual interaction. Similarly, other parts of the paper and conclusions may need updating. Finally, as to the comments on Figure 15 – improve as you discussed in your reply. Next to that, it may be useful to also show one (or all) of the subplots with the wake and using the full color range (+ clear explanation in caption).

Sincerely,
Johan Meyers

Thank you for the nice revision.