Mean and fluctuating helicity in swirling jet flows

Tomographic particle image velocimetry measurements of turbulent swirling jets open new explorations of mean and pulse components and pattern dynamics. We present direct experimental evidence of turbulent helicity cascade from large scales to small scales. We map the distributions of mean and fluctuating helicity components-the revealing anisotropic structure of helical jet flow. We show that a scenario of helicity generation and decay along the jet depends dramatically on the inflow swirl. The obtained results provide valuable materials to benchmark the modern numerical simulations with a turbulent closure technique.