Stokes number effects on particle slip velocity in wall-bounded turbulence and implications for dispersion models

The particle slip velocity is adopted as an indicator of the behavior of heavy particles in turbulent channel flow. The statistical moments of the slip velocity are evaluated considering particles with Stokes number, defined as the ratio between the particle response time and the viscous time scale of the flow, in the range 1 < St < 100. The slip velocity fluctuations exhibit a monotonic increase with increasing particle inertia, whereas the fluid-particle velocity covariance is gradually reduced for St ⩾ 5. Even if this covariance equals the particle turbulence intensity, a substantial amount of particle slip may occur. Relevant to two-fluid modeling of particle-laden flows is the finding that the standard deviation of the slip velocity fluctuations is significantly larger than the corresponding mean slip velocity.

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