arXiv subjects

J. M. O. Massey

Publications and source records attributed to J. M. O. Massey.

3 recordsLinked to original sources

arXiv2026

A source-term interpretation of turbulent rough wall-pressure spectra

Wall-pressure fluctuations beneath a turbulent boundary layer drive the flow-induced noise and structural loading of rough surfaces. On a smooth wall their variance grows with the logarithm of the Reynolds number, a growth carried, in a source-term reading, by the nonlinear turbulence--turbulence part of the pressure source acting across the logarithmic layer. We ask what sets the same growth once the wall is fully rough. Standard rough-wall phenomenology answers it: above the roughness the mean flow keeps its smooth-wall logarithmic form, so the active source range is cut off at the roughness height rather than the viscous length, and the variance grows on the logarithmic span between the roughness height and the layer thickness in place of the Reynolds number. Splitting the pressure source into its two physical parts then distinguishes separate contributions to the energy: a roughness-local one from the mean-shear source, fixed at high frequency on the roughness scale, and an energetic one from the nonlinear source at the outer scale, which alone carries the growth. Calibrated against rough-wall cases, the model collapses the spectral shape onto this energetic peak and holds it Reynolds-independent at fixed geometry. The canopy contribution decays with distance from the wall and contributes a finite offset. The growth coefficient is predicted to be the smooth-wall one. The present range is too narrow to discriminate that rate from twice or half it, so the contribution is a parameter-free prediction and the identification of a suitable roughness-size sweep that would test it.

physics.flu-dyn↗

arXiv2026

An Inner-Scaled Linear Contribution to Wall-Pressure Variance at High Reynolds Number

In canonical turbulent wall-bounded flows, the inner-scaled wall-pressure variance is empirically well described by a constant offset plus a slope logarithmic in the friction Reynolds number ($\dep$). Because the fluctuating pressure is predominantly a Poisson response to only two source terms -- a linear contribution from the mean shear coupled to a fluctuating velocity gradient, and a nonlinear contribution from the fluctuating velocity field -- the origin of this growth can be pinned down by elimination: if the linear source saturates at a Reynolds-number-independent value, the nonlinear source must carry the logarithmic growth. Here we supply the complementary evidence for inner-scaled invariance of the linear source at $\dep$ up to $O(10^4)$, using the simultaneous velocity and velocity-gradient hot-wire measurements of Zimmermann \textit{et al.} (2019 \textit{JFM}, vol. 869, pp. 182--213) acquired with a single eight-sensor probe in both a zero-pressure-gradient turbulent boundary layer and a high-Reynolds-number pipe flow. The inner-scaled factors entering the linear source collapse across Reynolds number, and the inertial-layer variance of the relevant fluctuating velocity gradient decays inversely with wall distance. Together with the established inner scaling of the mean shear, this is consistent with a linear wall-pressure contribution that, under inner normalisation, remains $O(1)$ as $\dep\to\infty$. Both source terms then trace to one structural mechanism: the near-wall depletion of mean spanwise vorticity that caps the linear source also feeds, through vortex stretching, the inertial-layer fissures that carry the growing nonlinear contribution.

physics.flu-dyn↗

arXiv2026

Data-Augmented Resolvent Analysis of Wall-Bounded High-Pressure Transcritical Flow

High-pressure transcritical fluid flows are central to modern energy and propulsion systems. A key challenge arises in confined configurations, where optimizing performance requires a detailed understanding of the coupled hydrodynamic and thermodynamic nonlinearities governing these flows. In this context, low-order decomposition techniques, particularly resolvent analysis, provide an interpretable linear input-output framework to identify and quantify dominant amplification mechanisms of coherent flow structures. This work pursues two main objectives: (i) to establish a resolvent-based framework tailored to high-pressure transcritical fluid flows, and (ii) to characterize the spatio-temporal sensitivity of the resolvent operator using data-driven turbulent base flows. These analyses identify flow responses and forcings that optimally enhance mixing and heat transfer, along with their characteristic scales. Results show that amplification is dominated by streamwise-elongated structures with spanwise periodicity, associated with peak singular values at normalized spanwise wavenumbers of order unity. Unlike ideal-gas or incompressible flows, the dominant forcings originate from thermodynamic fluctuations in the pseudo-boiling region. Linearization about the turbulent mean flow yields intensified responses in the form of coherent counter-rotating vortex pairs. Energetic-scale motions are constrained by the low-Reynolds-number and non-isothermal conditions considered, with a dominant spectral mode reaching streamwise lengths comparable to instantaneous structures. Data-driven analyses further reveal coherent motions propagating at phase speeds absent from classical incompressible wall-bounded turbulence, intensified near the pseudo-boiling region and constrained toward the hot wall.

physics.flu-dyn↗