a very interesting paper from the group of Prof. Anne Neville

dear collegues 

    hope you are well ---  I guess you may be interested to read that in a very accurate and elegant numerical study of adhesion in the presence of roughness, which I strongly recommend for its high quality on Roy Soc journal, prof. Anne Neville, FRS, leader in tribology in UK and elsewhere, finds an interesting conclusion, namely that  Finally, the effect of surface roughness on the adhesionbetween surfaces was studied, and it was shown that
the root mean square gradient of surface roughness
can change the adhesive pressures irrespective of
the root mean square surface roughness. We have
tested two adhesion parameters based on Johnson’s
modified criteria and Ciavarella’s model. We showed
that Ciavarella’s model introduces the most reasonable
criteria suggesting that the RMS roughness and large
wavelength of surfaces roughness are the important
parameters of adhesion between rough surfaces.
I guess it may be useful however to continue investigating this problem with much broader spectra.  I know prof Barber's student, Junki Joe, has the most elegant formulation around as a non linear differential diffusion equation generalizing Persson's approach, but it is not obvious how to solve some details.   Junki Joe's thesis will be a milestone in adhesive rough contact mechanics. Ghanbarzadeh, A., Faraji, M., & Neville, A. (2020). Deterministic normal contact of rough surfaces with adhesion using a surface integral method. Proceedings of the Royal Society A, 476(2242), 20200281.