MIX UNTRIM.DAT

Basic Information

File-Type

mix_untrim.dat

File-Form

FORMATTED

Version

1.0 / November 2007

Description-Date

December 2010

Significance of the File

contains general input Data for the package MIX

File-Contents (in Catchwords)

Input Steering Data

• General steering Data (Block Turbulence_Model)

• Key "Constant_Viscosity" : prescribed constant turbulent Viscosity and Diffusivity.
• Key "Zero_Equation_Model" : Zero Equation Models. No need to solve additional equations. (The models differs principaly in the way they compute the mixing length).
• Key "One_Equation_model" : One Equation Models. One additional equation for the turbulent kinetic energy has to be solved.
• Key "Two_Equation_model" : Two Equation Models. Two additional equations for the turbulent kinetic energy and the dissipation has to be solved.

Remarks on the following optional blocks:

• The user is requested to choose one of the methods listed above.
• Depending on the used method, the corresponding block below has to be filled.
• The last two blocks are optional

• Block Zero_Equation_Model.

• Key "Classical_Prandtl" : the mixing length is computed using the Prandtl approach.
• Key "Nezu_Model" : the mixing length is computed using the Nezu and Nakagawa appraoch.
• Key "Quetin_Model" : the mixing length is computed using the Quetin approach.
• Key "Tsanis_Model" : the mixing length is computed using the Tsanis approach.
  For the models listed above, a Damping Function which depends on the Richardson Number is used. Hence, the effect of flow stratification is taken into account (stable or unstable flows).
• Key "Rodi_Model" : the turbulent Viscosity is computed using the Rodi model. (for the mixing length, the approach after Nezu and Nakagawa is used by Rodi)
  The Rodi Model has a proper damping function for tracers which depends on the Richardson number. The damping of momentum is performed by a term that depends on the density gradient. This Term is introduced next to the velocity gradients..
• Key "DelftAlg_Model" : the turbulent Viscosity is computed using an Algebraic Closure Model . The friction velocity on the bed and at the free surface are used to derive the turbulent kinetic energy. To close the problem, the mixing length after Nezu and Nakagawa is used.
• Key "DelftAem_Model" : this model is a combination of DelftAlg_Model and Nezu_Model. The maximum of the two models is taken. In DelfAlg_Model and DelftAem_Model, the turbulent Viscosity damping function after Busch is used. For tracers, the Munk and Anderson damping function is implemented.

More informations are available in the document (ca. 120 kB) A Short Theoretical Description of the Mixing Length Models Implemented in the ProgHome Package MIX

• Block One_Equation_Model.

• In the one equation models, an additional equation for the TKE (turbulent kinetic Energy) needs to be solved. The Dissipation term E is derived from the KTE and other method specific parameters. Every single model has its own Damping function. Key "Norris_Reynolds" : the Dissipation is computed using the Norris Reynolds Model.
• Key "Hassid_Poreh" : the Dissipation is computed using the Hassid and Poreh Model.
• Key "Wolfstein" :the Dissipation is computed using the Wolfstein Model.

• Block Two_Equation_Model.

In the two equation models, the solution of two additional equations for the TKE and the Dissipation E is requested. The models are classified according to the Reynolds number. Practically, this is realized through the use of different damping functions.

• Key "K-E_Low" : the model K-E_Low is appropriated for low Reynolds numbers where the distance to the wall plays an important role.
• Key "K-E_High" : the model K-E_High is the standard case and is appropriated for high Reynolds numbers.

• (optional) Block Minimum_Visco_Diff.

Minimum default values for Diffusivity and Viscosity are implemented. The user is given the possibility to introduce his own minimum values. Additionally, the mimimum Diffusivity can be computed using the Ozmidov mixing length. The user has to define a weighting parameter between the Ozmidov mixing length and the mixing length of the method.

• (optional) Key "Minimum_Vis" : user defined minimum turbulent Viscosity. can be zero.
• (optional) Key "Minimum_Dif" : user defined minimum turbulent Diffusivity. can not be zero.
• (optional) Key "Ozmidov_Wei" : user defined weighting parameter for Ozmidovs mixing length.

• (optional) Block Constant_Visco_Diff.

For Diffusivity and Viscosity, default constant values are implemented. The user is given the possibility to introduce his proper values.

• (optional) Key "Constant_Vis" : user defined constante turbulent Viscosity.
• (optional) Key "Minimum_Dif" : user defined constante turbulent Diffusivity.

Programs using this Type of File

UNTRIM2, UNTRIM2007

Example-File

siehe $PROGHOME/examples/lib/mix/mix.dat

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