Modelling high Reynolds number wall-turbulence interactions in laboratory experiments using large-scale free-stream...

Area of Science:

• Fluid Dynamics
• Turbulence Research

Background:

• Canonical high Reynolds number turbulent boundary layers exhibit complex scale interactions.
• Free-stream turbulence influences near-wall flow dynamics, showing similarities to canonical boundary layers.

Purpose of the Study:

• To investigate scale interactions in the near-wall region of a turbulent boundary layer subjected to free-stream turbulence.
• To compare these interactions with those in canonical high Reynolds number turbulent boundary layers.
• To assess the potential for laboratory-scale experiments to simulate high Reynolds number wall turbulence.

Main Methods:

• Simultaneous hot-wire measurements from a multi-sensor rake.
• Traversing the rake through the boundary layer to capture near-wall and outer-layer data.
• Analysis focused on scale interactions and amplitude modulation in different flow conditions.

Main Results:

• Identified the footprint of large-scale eddies from the logarithmic region on near-wall small scales.
• Quantified the modulating interaction and phase differences in amplitude modulation between scales.
• Demonstrated similarities between free-stream turbulence-affected boundary layers and canonical high Reynolds number flows.

Conclusions:

• Turbulent boundary layers subjected to free-stream turbulence can effectively simulate high Reynolds number wall turbulence interactions.
• Fundamental scale interactions in high Reynolds number flows are achievable at laboratory scales.
• Findings have positive implications for developing high-fidelity models of wall turbulence.