Investigation of fundamental flow mechanisms over a corrugated waveform using proper orthogonal decomposition and spectral analyses

• Experimental investigation of the fundamental flow mechanisms over a waveform.
• The impact of waveform geometry and wall heating on the turbulent flow structure was investigated.
• Proper orthogonal decomposition and spectral analysis were used to identify the flow features.

This study investigates the interactions between the underlying turbulent features that together make up the complex flow behaviour observed in corrugated channel flows. Higher order analyses using proper orthogonal decomposition (POD) and wavenumber spectra were conducted on the turbulent velocity data for heated and unheated air flow through the channel. Results showed that at a given flow rate, the turbulent flow energy was produced by the corrugation and transported into the bulk flow at both heated and unheated conditions. At low flow rates, the heated wall increased the total turbulent energy and affected its distribution across the modes. Strong energies were seen close to the corrugations, which contributed to sustaining structures at higher modes, while the flow energy was more evenly distributed for the unheated condition. At the highest flow rate, the energy strength and distribution was very similar at low modes (n ≤ 20) and heating effects were most prominent at high modes with higher energies associated with small-scale flow patterns. It is observed that the corrugation waveform has a larger impact on the turbulence generation compared to heating. The addition of heat primarily increased and maintained the strength of turbulent structures.