How low for low Reynolds model?
How low is the reynolds number in turbulence to use the low reynolds number source terms? 100 maybe 50 maybe 1000? what tests has phoenics done for this case to compare with experiments? which model is best for jets and plumes?

Re: How low for low Reynolds model?
LowReynoldsnumber turbulence models are designed to account for the effects of molecular viscosity on turbulence near walls. Therefore such models are valid throughout the viscous, transition and turbulent regimes in nearwall turbulence.
As an example consider the LamBremhorst ke model to see how wthe model coefficients depend on turbulent Reynolds number. The model differs from the standard highReynoldsnumber form in that the empirical coefficients CMUCD, C1E and C2E are multiplied respectively by the functions: FMU = [ 1.EXP(0.0165*REYN) ]**2 (1.+20.5/REYT) F1 = 1.+(0.05/FMU)**3 F2 = 1.EXP(REYT**2) where REYN = SQRT(KE)*YN/ENUL REYT = KE**2/EP/ENUL where YN is the distance to the nearest wall. For highturbulence Reynolds numbers REYN or REYT, the functions FMU, F1 and F2 multiplying the three constants tend to unity. This model and other ke variants plus the WilcoxKolmogorov model have been tested extensively against nearwall data. Many example Q1 input files can be found in the advancedturbulencemodel and core libraries of a PHOENICS Installation. Some example applications are reported on CHAM's website at: http://www.cham.co.uk/phoenics/d_pol...flows/cava.htm http://www.cham.co.uk/phoenics/d_pol...ws/impinga.htm Note that such lowRe models are not formally valid for free flows at low turbulent Reynolds numbers, such as the farfield axisymmetric wake where the turbulent Reynolds number decays with distance from the origin. Which model is best for jets and plumes? It depends on the precise configuration. For example, even the standard ke model is useless for a simple axisymmetric free jet unless it is modified. The standard model also fails to predict the plane wall jet correctly. Thus, universality cannot be expected of a turbulence model. Plumes usually require buoyancy corrections to the standard ke model, but this area has been well researched and successful publications abound in the literature using PHOENICS and other software. 
Re: How low for low Reynolds model?
Thanks you.

Very Good Answer.
(1). The answer is excellant. "very high quality " answer. Thank you very much. (2). This answer can be used to "measure" the user's understanding of the turbulence modeling. (3). I would like to add one more item: the book by David Wilcox " turbulence modeling for CFD " is an excellant book for anyone in CFD field.

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