A Spectral Proper Orthogonal Decomposition Analysis of Turbulent Flow Around a High-Rise Building

This study presents a high-fidelity Large Eddy Simulation (LES) investigation of turbulent flow over a high-aspect-ratio (AR = 7) wall-mounted rectangular cylinder, representative of a vertiport structure, under varying inflow turbulence conditions. A volumetric momentum source term is coupled with a synthetic turbulence generation method to emulate urban atmospheric disturbances with turbulence intensities of 5% and 10%. The effectiveness of this hybrid turbulence modeling approach is validated through power spectral density analysis and comparison with the target von Kármán spectra. Spectral Proper Orthogonal Decomposition (SPOD) is employed to extract coherent structures in the wake, revealing dominant modes at Strouhal numbers ���� ≈ 0.1, 0.2, and 1.8. A Kelvin–Helmholtz-like shear layer instability near the top of the vertiport is identified as the primary contributor to energetic fluctuations at ���� ≈ 1.8. The introduction of turbulence disrupts the periodicity and coherence of this structure, resulting in a noticeable reduction in SPOD energy at the dominant flapping frequency, although its spectral signature persists. Pressure coefficient visualizations further indicate that this structure exhibits a characteristic streamwise length of approximately 20% of the vertiport width and extends up to 40% of the width above the platform. For a typical vertiport size of 10 m, this corresponds to a 2 m structure reaching 4 m in height—dimensions that could pose significant aerodynamic and control challenges for eVTOL vehicles with rotor diameters on the order of 1 m. The findings highlight the critical importance of incorporating realistic inflow turbulence in the assessment of coherent aerodynamic structures and their potential impact on Urban Air Mobility (UAM) operations.