The Effect of Boundary Conditions on Three-Dimensional Turbulent Flow
Date Issued
2008
Date
2008
Author(s)
Ferguson, Alexander
Abstract
The effect of boundary conditions on 3D turbulent flow is studied by the Direct Numerical Simulation of an initially homogeneous and isotropic velocity field under forced and freely decaying conditions. Simulations are performed for both Channel (Plane) and Box flows and code validation is conducted by simulations of decaying box turbulence confirming a power-law decay of energy and Reynolds number with time. he change in energy decay rate for plane flow is explained in terms of the transfer of energy between stream-/span-wise directions and a potential equilibrium state. No-slip boundary conditions not only increase the viscous shear forces within the system, but also inhibit the cascade of energy through the inertial sub-range range. The presence of Kolmogorov spectra in Plane flow is observed at lower Reynolds number than possible for Box flow. Very low Reynolds number simulations of forced turbulence, show that eventually both plane and box turbulence flows give similar spectra, owing to the increased effectiveness of viscous forces in removing energy from low wave-numbers.t is concluded that boundary conditions give rise to additional stresses within the system that dampen normal-wise components of velocity, transfer energy out into the main flow and inhibit the cascade process resulting in the presence of Kolmogorov spectra where, under similar conditions, Box turbulence shows no such phenomena.
Subjects
Boundary Conditions, 3D, Turbulence, Simulation, Numerical
Type
thesis
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