This paper is the second part of a series of three papers dedicated to the prediction of low-speed interaction noise of an isolated Contra-Rotating Open Rotor (CROR). The objective is to investigate the URANS chorochronic approach for computing the unsteady flow across both rotors. The stress is to be put on the correct description and propagation of the wake deficit, which is essential for capturing the unsteady loading onto the rear row and thus the resulting interaction noise. Chorochronic methods are attractive because they require the computation of a single channel only and thus are less costly than full-annulus CFD computations (such as sliding mesh or Chimera techniques). Therefore, the chorochronic technique is used in this study to investigate various mesh topologies. It is shown that the method presents very good agreement with experimental data in absolute levels at a very reasonable cost. Nomenclature BPF= Blade Passage Frequency mR = Rear rotor tones frequency, m×BPF (rear rotor) nF = Front rotor tones frequency, n×BPF (front rotor) nF+mR = Rotor-to-rotor tones frequency, n×BPF (front rotor) + m×BPF (rear rotor) N i = number of blades of the row i R i = radius of rotor i RPM = Revolutions Per Minute SPL = Sound Pressure Level T choro = Chorochronic period T i = Relative period of row i Ω i = rotational speed of blade row i

A system with macrodiversity selection combining (SC) receiver and for microdiversity equal gain combining (EGC) receivers is considered. Received signal is subjected, simultaneously to multipath fading and shadowing, resulting in signal envelope and signal power variation. Closed form expressions for moments of macrodiversity SC receiver output signal envelope are calculated. Numerical expressions are plotted to present the influences of Gamma shadowing severity and Nakagami-m severity on moments of proposed system output signal.

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