Question

From which of these terms does the turbulent viscosity arise from?

(a) \(\frac{\partial(\overline{\rho}\tilde{u})}{\partial t}\)

(b) \(-\frac{\partial\tilde{p}}{\partial x} \)

(c) \(div(\mu grad\widetilde{(\vec{V})})\)

(d) \(\frac{\partial\overline{(\overline{\rho}u{‘}v{‘})}}{\partial y}\)

This question was addressed to me at a job interview.

This question is from Turbulence Modelling topic in section Turbulence Modelling of Computational Fluid Dynamics

Answer 1

The correct answer is (d) \(\frac{\partial\overline{(\overline{\rho}u{‘}v{‘})}}{\partial y}\)

For explanation: The term \(\overline{(\overline{ρ}u’v’)}\) represents the turbulent shear stress (Reynolds stress) in the momentum equation. This leads to the turbulent or eddy viscosity in the turbulent models.