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Erschienen in:
01.01.2018 | Research Article
Behaviour of the energy dissipation coefficient in a rough wall turbulent boundary layer
Erschienen in: Experiments in Fluids | Ausgabe 1/2018
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Abstract
Hot-wire anemometry measurements are made in a rough wall turbulent boundary layer to assess the dependence of the mean turbulent kinetic energy dissipation coefficient, \(C_\varepsilon\), on the distance from the wall and the Taylor microscale Reynolds number, \(Re_\lambda\). The locally isotropic expression \(\langle \varepsilon _\mathrm{{iso}}\rangle\) is used as a surrogate for the mean turbulent kinetic energy dissipation rate, \(\langle \varepsilon \rangle\), for calculating \(C_\varepsilon =\langle \varepsilon \rangle L/u^{\prime 3}\); L and \(u'\) are the integral length scale and the rms of the longitudinal velocity fluctuation, respectively. The measurements show that \(C_\varepsilon\) varies significantly near the wall, but becomes almost constant in the region \(0.2 \le y/\delta \le 0.6\) of the boundary layer, a region where \(Re_\lambda\) is also practically constant.