There are several ways how to archive it. One possible approach might be with help of trigonometric functions (in the attached sample scene the acos one) to calculate the angle of those rotated panels linked to the "opening width".
Another way would by defining the number of panels & adjusting the percentage to drive the style. To get the correct number of repetitions, there is an exported Counter Sequence parameter of the second Sequence Operator.
As usually, there's not just one correct way, so please feel to experiment with these examples to get the one, that'll best suit to your needs (parameters). Hope you'll find attached approaches useful.