Dispersion of a passive scalar in turbulent open channel flow

Bomminayuni, Sandeep Kumar; Stoesser, Thorsten

doi:10.1201/b17133-25

Cited by 2 publications

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“…The transport of active or passive scalar quantities within a given flow domain is governed by advective and diffusive processes where turbulence plays a key role in their mixing and distribution. In fact, processes such as the transport of pollutants or the injection of a tracer [7, 8] are often treated as passive scalar quantities. Understanding how a turbulent separated flow impacts the transport of a passive scalar can be of particular interest in environmental applications such as sediment deposition, channel scour [27], sidewall erosion, tracer dye transport [3, 4] and pollutant dispersion [16].…”

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confidence: 99%

Instantaneous transport of a passive scalar in a turbulent separated flow

et al. 2017

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The results of large-eddy simulations of flow and transient solute transport over a backward facing step and through a 180°bend are presented. The simulations are validated successfully in terms of hydrodynamics and tracer transport with experimental velocity data and measured residence time distribution curves confirming the accuracy of the method. The hydrodynamics are characterised by flow separation and subsequent recirculation in vertical and horizontal directions and the solute dispersion process is a direct response to the significant unsteadiness and turbulence in the flow. The turbulence in the system is analysed and quantified in terms of power density spectra and covariance of velocity fluctuations. The injection of an instantaneous passive tracer and its dispersion through the system is simulated. Large-eddy simulations enable the resolution of the instantaneous flow field and it is demonstrated that the instabilities of intermittent largescale structures play a distinguished role in the solute transport. The advection and diffusion of the scalar is governed by the severe unsteadiness of the flow and this is visualised and quantified. The analysis of the scalar mass transport budget quantifies the mechanisms controlling the turbulent mixing and reveals that the mass flux is dominated by advection.

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