DimensionalizeAction

Overview

The DimensionalizeAction action is responsible for fetching the characteristic scales from the user and applying them to dimensionalize any field passed from NekRS into MOOSE (AuxVariables, Postprocessors, UserObjects, etc.). To use, add a [Dimensionalize] block inside the [Problem] block.

Cardinal assumes that the NekRS inputs were nondimensionalized with the following:

$$u_i^\dagger\equiv\frac{u_i}{u_{ref}}$$(1)

$$P^\dagger\equiv\frac{P}{\rho_0u_{ref}^2}$$(2)

$$T^\dagger\equiv\frac{T-T_{ref}}{\Delta T}$$(3)

$$x_i^\dagger\equiv\frac{x_i}{L_{ref}}$$(4)

$$t^\dagger\equiv\frac{t}{L_{ref}/u_{ref}}$$(5)

where $\dagger$ superscripts indicate nondimensional quantities. U is used to specify $u_{ref}$, T is used to specify $T_{ref}$, dT is used to specify $\Delta T$, L is used to specify $L_{ref}$, rho is used to specify $\rho_0$, and Cp is used to specify $C_{p,0}$ (which does not appear above, but is necessary for scaling a volumetric heat source). Finally, the mesh mirror must be in the same units as used in the coupled MOOSE application, so the scaling parameter on NekRSMesh must be set to dimensionalize the nondimensional .re2 mesh. In other words, scaling must be set to $L_{ref}$.

For passive scalars, NekRS allows each to be dimensionalized in a manner similar to temperature,

$$s_{i}^\dagger=\frac{s_i-s_{i,ref}}{\Delta s_i}$$

s01, s02, and s03 are used to indicate the $s_{i,ref}$ for scalars 1, 2, and 3, respectively. ds01, ds02, and ds03 are used to indicate the $\Delta s_i$ for scalars 1, 2, and 3, respectively.

For example, suppose your NekRS input is in non-dimensional form. Applying a NekVolumeAverage postprocessor to temperature would be used to evaluate a volume average of temperature.

[Postprocessors]
  [avg_T]
    type = NekVolumeAverage
    field = temperature
  []
[]

If the NekRS inputs are properly non-dimensionalized and the correct scales are provided to this class, then temperature is non-dimensionalized according to Eq. (3) and volume is non-dimensionalized according to Eq. (4), or

$$V^\dagger=\frac{V}{L_{ref}^3}$$(6)

The NekVolumeAverage postprocessor is then computed directly on the NekRS solution (in non-dimensional form) to give

$$p_{nd}=\frac{\int T^\dagger dV^\dagger}{\int dV^\dagger}$$(7)

where $p_{nd}$ is the value of the postprocessor in non-dimensional form. Before returning the value of the postprocessor, Eq. (7) is dimensionalized by applying the scales in Eq. (3) and Eq. (6) to give the

$$p=\frac{\int T^\dagger dV^\dagger}{\int dV^\dagger}+\frac{T_{ref}}{\Delta T}$$(8)

where $p$ is the value of the postprocessor in dimensional form (which is what is actually returned by the postprocessor).

Example Input File Syntax

An example where the NekRS input files are set up in non-dimensional form,

[Problem]
  type = NekRSProblem
  casename = 'msfr'
  output = 'temperature'

  synchronization_interval = parent_app

  [Dimensionalize]
    L = 1.0
    U = '${fparse Re * mu / rho}'
    T = '${fparse 625.0 + 273.15}'
    dT = 100.0
    rho = ${rho}
    Cp = 1524.86 # J/kg/K
  []

  normalization_abs_tol = 1e6
  normalization_rel_tol = 1e-3
[]

Input Parameters