Abstract
The paper deals with the stochastic generation of synthesized turbulence, which may be used for a generating of an inlet boundary condition for unsteady simulations, e.g. Direct Numerical Simulation (DNS) or Large Eddy Simulation (LES). Assumptions for the generated turbulence are isotropy and homogeneity. The described method produces a stochastic turbulent velocity field using the synthesis of a finite sum of random Fourier modes. The calculation of individual Fourier modes is based on known energy spectrum of turbulent flow, and some turbulent quantities, e.g. turbulent kinetic energy and turbulent dissipation rate. A division of wave number range of the energy spectrum determines directly the number of Fourier modes, and has a direct impact on accuracy and speed of this calculation. Therefore, this work will examine the influence of the number of Fourier modes on a conservation of the first and second statistical moments of turbulent velocity components, which are prespecified. It is important to ensure a sufficient size of a computational domain, and a sufficient number of cells for meaningful comparative results. Dimensionless parameters characterizing the resolution and size of the computational domain according to a turbulent length scale will be introduced for this purpose. Subsequently, the sufficient values of this parameters will be shown for individual numbers of Fourier modes.
Highlights
It is well known that the inlet boundary condition (BC) has a significant effect on solution, especially for unsteady simulations
The stochastic method described bellow is based on the approach devised by Kraichnan [1] and improved by Karweit et al [2], where the spatially correlated turbulent velocity field is defined as a finite sum of discrete Fourier modes
This paper describes the stochastic method for generating random turbulent velocity field with the space-time correlation
Summary
It is well known that the inlet boundary condition (BC) has a significant effect on solution, especially for unsteady simulations. The stochastic method described bellow is based on the approach devised by Kraichnan [1] and improved by Karweit et al [2], where the spatially correlated turbulent velocity field is defined as a finite sum of discrete Fourier modes. This method was originally used for generating a turbulent velocity field from the turbulent quantities obtained by RANS simulation, and subsequent computing of acoustic source terms as a right hand side of an appropriate propagation equations of sound waves. A further development of this method for generating a turbulent inlet BC was proposed by Davidson [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
