There are indeed additional parameters. We have added a complete list to Section 2.8. Many are explored to some extent in the results (beta, reversal frequency, domain dimensions, trichome R7 density), whereas most of the physical characteristics of the trichomes are known from published sources (diameter, length, gliding speed, bending modulus), and finally N was simply chosen so that trichomes had a “smooth” appearance.
If I understand correctly, there are six important length scales in the problem, the size of the domain DH , the spacing between trichomes 13 ρ − , 0 , , L l αν ζ = Θ, and the trichome length L = Nl (also denoted L in the manuscript), giving five dimensionless numbers. However, in the non-dimensionalization, the authors state that there are only two parameters: ρ and Nl γ θ = . Unless I am mistaken, there are additional parameters like l/L, Nl/D, and N that the authors hold fixed but may influence the details of the numerics.