arXiv:2108.10833v1 [physics.flu-dyn] 24 Aug 2021 This draft was prepared using the LaTeX style file belonging to the Journal of Fluid Mechanics 1 Resolvent analysis of pressure fluctuations in turbulent channel flows Filipe R. Amaral 1 † and André V. G. Cavalieri 1 1 Divisão de Engenharia Aeronáutica, Instituto Tecnológico de Aeronáutica, São José dos Campos, SP 12228-900, Brazil (Received xx; revised xx; accepted xx) We study pressure fluctuations in direct numerical simulations (DNS) of turbulent chan- nel flows at friction Reynolds numbers of approximately 180 and 550, by a comparison between analysis of DNS data and resolvent analysis considering a linearization around the mean turbulent profile. Dominant structures are extracted from the DNS data using wavenumber and frequency spectra, and spectral peaks, which comprise near- wall, large-scale and spanwise-coherent structures, are further analyzed using spectral proper orthogonal decomposition (SPOD). SPOD analysis, employing a pressure inner product, show a strong dominance of the leading mode, highlighting low-rank behaviour of pressure fluctuations. The leading resolvent mode, considering pressure as output, agrees closely with the first SPOD mode, providing support to recent studies that showed better performance of resolvent-based estimators when predicting pressure fluctuations compared to velocity structures (Amaral et al. arXiv:2011.06525 , 2021). However, non- linear terms extracted from the DNS data, corresponding to forcing in resolvent analysis, also display low-rank behavior, with dominant modes that differ from optimal forcings from resolvent analysis. The dominant mechanisms of analyzed modes are seen to be the generation of streamwise or spanwise vortices, with pressure fluctuations appearing close to vortex centers. A study on the nonlinear terms individual contributions to the pressure output reveals that each forcing component plays a constructive role to the input-output formulation, which simplifies modeling of forcing color. The present results further encourage the use of simplified linear models to study wall turbulence, especially if pressure fluctuations are of primary interest. Key words: Authors should not enter keywords on the manuscript, as these must be cho- sen by the author during the online submission process and will then be added during the typesetting process (see http://journals.cambridge.org/data/relatedlink/jfm-keywords.pdf for the full list) 1. Introduction The understanding of pressure fluctuations in wall-bounded turbulent flows is of funda- mental importance for many practical applications such as sound radiation and struc- † Email address for correspondence: filipefra@ita.br