Rapid distortion theory of turbulent flow around a porous cylinder

Abstract

Abstract

Experimental investigation of turbulent coherent structures interacting with a porous airfoil

“…These similarities suggest a potential link between attenuation in turbulence distortion and noise reduction and are consistent with the conclusions drawn by Zamponi et al (2021) using the rapid distortion theory. As stated in this study, a better understanding of the turbulence-porous structure interaction and, specifically, of the alteration of the twodimensional energy spectrum of the upwash turbulent velocity may lead to the elaboration of a novel noise-mitigation predictive model for porous airfoils based on Amiet's theory.…”

Experimental and Analytical Investigation of the Distortion of Turbulence Interacting with a Porous Airfoil

“…The RDT predictions feature the same trend and the same ∆Φ U U as the experimental results at low St, although the turbulence downstream of the rod does not meet the condition of homogeneity and isotropy assumed by the theory [29]. This suggests that the relative alterations in turbulence distortion due to porosity are independent of the nature of the upstream flow.…”

“…However, deviations occur in correspondence with the frequency peak related to the vortex shedding in the wake of the upstream rod, which is not modeled in the present case. Furthermore, the analytical results exhibit an underprediction at high St that can be attributed to the limitations in the spatial-wavenumber domain considered in the theory, as explained in [29].…”

“…Indeed, previous experimental studies [11,57] have demonstrated that, in a region sufficiently close to the stagnation point, the inflow distortion experienced by an airfoil is similar to that caused by a cylinder that has the same radius as the tangent circle at the airfoil leading edge. The porous RDT model developed by Zamponi et al [29] will be employed in this case. For more information about the model, the interested reader is referred to the aforementioned paper.…”

“…Subsequently, the power spectra of the velocity fluctuations measured by the hot-wire are computed in order to analyze whether they can be linked to the acoustic power spectra. Finally, the experimental results will be compared with the analytical prediction given by the RDT model recently proposed by Zamponi et al [29], who extended the theory in order to account for a porous body.…”