Two-point correlation of synthetic fluctuations
Two-point correlation of syntehic fluctuations

How to Implement Synthetic Inlet Boundary Conditions



Publications: [1, 4]


Description
A method to prescribe synthesized turbulent inlet boundary conditions is given. When making LES, DES or hybrid LES-RANS a precursor channel DNS is often used. The disadvantage of this method is that it is difficult to re-scale the DNS fluctuations to higher Reynolds numbers.

The synthesized isotropic turbulent fluctuations are generated at the inlet plane with a prescribed turbulent length scale and energy spectrum. A large number of independent realizations are generated. When running the unsteady CFD code a correlation in time between these realization is introduced via an asymmetric, non-truncated time filter. In this way the turbulent time scale of the synthesized isotropic turbulent fluctuations is prescribed.

Downloads
Here Matlab files can be donwloaded to generate synthetic fluctuatations described above. The method is described in detail in the PDF files (see References below).


Movie
  Movies which show synthetic inlet fluctuations.

Integral time scale=0.015, computational time step=0.000625 (a=0.95, b=0.3)
Integral length scale=0.13
Colors show u'.

movie (7.2MB)

Integral time scale=0.015, computational time step=0.000625 (a=0.95, b=0.3)
Integral length scale=0.40
Colors show u'.

movie (7.2MB)
 


 

 
REFERENCES
  1. L. Davidson
    "Using Isotropic Synthetic Fluctuations as Inlet Boundary Conditions for Unsteady Simulations" Advances and Applications in Fluid Mechanics, Vol. 1(1), pp. 1-35, 2007.
    View PDF file
     
  2. L. Davidson
    "HYBRID LES-RANS: Inlet Boundary Conditions for Flows Including Recirculation", 5th International Symposium on Turbulence and Shear Flow Phenomena, Vol. 2, pp. 689-694, 27-29 August, Munich, Germany, 2007.
    View PDF file
     
  3. Appendix: "Computation of wavenumber vector and angles"
    View PDF file
     
  4. L. Davidson
    "Inlet fluctuating boundary conditions for 3D Hill Flow"
    View PDF file
     
  5. L. Davidson and S.-H. Peng
    "Embedded LES Using PANS", I6th AIAA Theoretical Fluid Mechanics Conference, AIAA paper 2011-3108 27 - 30 Jun 2011, Honolulu, Hawaii.
    View PDF file
     
  6. L. Davidson
    "Large Eddy Simulation of Heat Transfer in Boundary Layer and Backstep Flow Using PANS", Turbulence, Heat and Mass Transfer 7 Hanjalic, Y. Nagano, D. Borello and S. Jakirlic (Editors), Begell House, Inc., 2012
    View PDF file
     
  7. L. Davidson and S.-H. Peng
    "Embedded Large-Eddy Simulation Using the Partially Averaged Navier-Stokes Model", AIAA J, Vol. 51(5), pp. 1066-1079, 2013. DOI
     


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