********* Viscosity ********* :: Viscosity = {model_name} {float_list} [M/Lt] ----------------------- **Description / Usage** ----------------------- This card is used to specify the viscosity model for the liquid constitutive equation (see Sackinger et al., 1995). Definitions of the input parameters are as follows: +-----------------+----------------------------------------------------------------------------------------------------+ |{model_name} |The name of the viscosity model, which can be one of the following: **CONSTANT, USER, USER_GEN**, or| | |**FILL, LEVEL_SET, CONST_PHASE_FUNCTION**. | +-----------------+----------------------------------------------------------------------------------------------------+ |{float_list}. |One or more floating point numbers ( through ) whose values are determined by the | | |selection for {model_name}. These are identified in the discussion of each model below. Note that | | |not all models employ a {float_list}. | +-----------------+----------------------------------------------------------------------------------------------------+ Thus, +---------------------------------------------------------------------------------------+---------------------------------------------------------------------------+ |**CONSTANT** |This option specifies a constant viscosity for a Newtonian fluid. The | | |{float_list} has a single value: | | | | | | * - value of viscosity | +---------------------------------------------------------------------------------------+---------------------------------------------------------------------------+ |**USER** ... through and passed to the routine as an | | |array. | +---------------------------------------------------------------------------------------+---------------------------------------------------------------------------+ |**USER_GEN** ... |This option specifies that the viscosity will be given by a generalized | | |user-defined model. This user-defined model must be incorporated by | | |modifying the routine “usr_viscosity_gen” in the file user_mp_gen.c. Any | | |number of parameters can be passed (via through ) in here.| +---------------------------------------------------------------------------------------+---------------------------------------------------------------------------+ |**FILL** |The {float_list} for this option requires two values. It invokes a FILL | | |dependent viscosity that is set to the value of *float1* if the FILL | | |variable is 1 and *float2* if the FILL variable is 0. | +---------------------------------------------------------------------------------------+---------------------------------------------------------------------------+ |**LEVEL_SET** |This model is used to vary the viscosity in the flow region when a level | | |set function is used to track the boundary between two fluids using level | | |set interface tracking. This choice assures a smooth transition in density | | |across the zero level set contour. The {float_list} contains three values | | |for this model, where: | | | | | | * Fluid viscosity in the negative regions of the level set | | | function, μ- | | | * Fluid viscosity in the positive regions of the level set | | | function, μ+ | | | * Length scale over which the transition occurs, :math:`\alpha` .| | | If this parameter is set to zero, it will default to one-half the Level | | | Set Length Scale value specified elsewhere in the input deck. | | | | | |**Note**: a better way to specify the identical viscosity model is to make | | |use of the 2nd Level Set Viscosity card documented also in this manual. | +---------------------------------------------------------------------------------------+---------------------------------------------------------------------------+ |**CONST_PHASE_FUNCTION** |This model is used to vary the viscosity in the flow regime when phase | | |functions are used to track the motion of muliple phases. This choice | | |assures a smooth transition in viscosity across the phase boundaries. The | | |{float_list} contains a variable number of values that depend on the number| | |phase functions being tracked, where: | | | | | | * list of float variables equal to the number of phase | | | functions. These are the constant viscosities associated with each | | | phase in order from 1 to number of phase functions. | | | * Length scale over which the transition between one phases | | | viscosity value to theother occurs, :math:`\alpha` . If this parameter | | | is set to zero, it will default to one-half the Level Set Length Scale | | | value already specified. | | | * The “null” value for viscosity. This is the value for viscosity| | | which will be assigned to those regions of the flow where all the phase | | | functions are less than or equal to zero. | | | | | |The user should examine the **CONST_PHASE_FUNCTION** density model for a | | |detailed description of the relations used to compute viscosity with this | | |model. That model refers to densities but the same equations apply if | | |viscosities are exchanged for densities. | +---------------------------------------------------------------------------------------+---------------------------------------------------------------------------+ |**TABLE** {LINEAR | BILINEAR} [integer2] [FILE = filenm]|Please see discussion at the beginning of the material properties chapter 5| | |for input description and options. Currently the only valid options for | | |character_string1 is **TEMPERATURE** and **MASS_FRACTION**. | +---------------------------------------------------------------------------------------+---------------------------------------------------------------------------+ ------------ **Examples** ------------ The following is a sample card that sets the viscosity to USER: :: Viscosity = USER 1. 1. 1. 1. 1. :: Viscosity = LEVEL_SET 0.083 0.0001 0.1 ------------------------- **Technical Discussion** ------------------------- The viscosity specified by this input card is used with the **NEWTONIAN** *Liquid Constitutive Equation*. -------------- **References** -------------- Sackinger, P. A., Schunk, P. R. and Rao, R. R. 1995. "A Newton-Raphson Pseudo-Solid Domain Mapping Technique for Free and Moving Boundary Problems: A Finite Element Implementation", J. Comp. Phys., 125 (1996) 83-103.