PHASTA/Restart Ordering

Knowledge of the ordering of restarts is most useful for the creation of .pht or .phts files (used to tell ParaView what to read in from restarts in POSIX or SyncIO format respectively). There are both standard outputs from PHASTA that will be written no matter what, and optional ones that may depend on the simulation type or what type of analysis is planned on being done.

In the following, index numbering will be in index-by-1 format, or Fortran format. When creating a .pht or .phts file and filling in the start_index_in_phasta_array=" " section for each field, note that you should subtract one as ParaView reads this file using index-by-0.

Standard Outputs

The output flow variables written to restarts are NOT dependent on the choice of variables used to solve a given setup. PHASTA will always write pressure, velocity, and temperature (in that order) for both compressible and incompressible for the sake of consistency. If the incompressible formulation is being used without a temperature solve, the temperature field will still exist but will simply be all zeros. These output flow variables are stored under the header solution

In the case where turbulence models are being used or species are being solved for, solution will also populate scalar fields starting in the 6th field in sequential ordering:

• Scalar 1
• Scalar 2

The final ordering is then:

Pressure Primitive Fields

Field Number	Description	Notes
1	Pressure
2:4	Velocity	Vector quantity, ordered u, v, w
5	Temperature	This field can be ignored if incompressible
6	Scalar 1	Only written if scalar 1 exists
7	Scalar 2	Only written if scalar 2 exists

The exact quantity that any scalar represents depends on the models being used, though as some examples, for the Spalart-Allmaras (SA) 1-equation RANS model or DES/DDES formulations using the SA model, scalar 1 will be &nu _t. Some branches of the code may have the ability to solve more scalar equations and those extra scalars will be appended, in order, to the end of the solution field.

Time Derivatives

The time derivatives of all of the above fields are also present in the restarts, under the header time derivative of solution. These fields are in the exact same order as in solution, and are subject to the same caveats about how many scalars there may be and what they actually represent for any given branch of the code and simulation setup.

Pressure Primitive Fields

Field Number	Description	Notes
1	Time derivative of pressure
2:4	Time derivative of velocity	Vector quantity, ordered u, v, w
5	Time derivative of temperature	This field can be ignored if incompressible
6	Time derivative of scalar 1	Only written if scalar 1 exists
7	Time derivative of scalar 2	Only written if scalar 2 exists

Optional Outputs

Wall Distance

This quanity is simply a measure of the distance from any given node to the nearest wall point in the simulation. This quantity is mostly used in turbulence models but can be useful for the post-processing of complex domains

• Header: dwal
• solver.inp flag: placeholder

Fields

Field Number	Description	Notes
1	Wall Distance

Vorticity

• Header: vorticity
• solver.inp flag: Print vorticity: True

Fields

Field Number	Description	Notes
1:3	Vorticity	Vector quantity, ordered ωx, ωy, ωz
4	Magnitude of vorticity
5	Q	Defined as the second invariant of the velocity gradient tensor

Time Averaged Statistics (point-wise)

Point-wise time averaged statistics are useful for problems where there are no homogeneous directions in the flow to accumulate an average along. Instead, PHASTA can accumulate averages at each individual node. Note that this formulation only accumulates per-run, so an average is only computed from the start step of the current run, and total averages must be computed by adding successive averages with the appropriate weighting.

• Header: ybar
• solver.inp flag: Print ybar: True

Fields (incompressible)

Field Number	Description	Notes
1	Average velocity	Vector quantity, ordered u, v, w
2:4	Average pressure
5	Average speed
6:8	Average of the square of velocity	Vector quantity, ordered u2, v2, w2
9	Average of the square of pressure
10:12	Average of velocity cross-components	Vector quantity, ordered uv, uw, vw
13	Average of scalar 1
14:16	Average of vorticity	Vector quantity, ordered ωx, ωy, ωz
17	Average vorticity magnitude
18	Average of scalar 2

Average of Q may be in position 19 depending on the branch

Wall Shear Stress

This field is only defined at wall points and is used to get the most accurate measure of the wall shear stress possible as otherwise a finite gradient using the first point off of the wall must be implemented, which may or may not be normal to a wall point underneath of it.

• Header: wss
• solver.inp flag: Print Wall Fluxes: True (check this)

Fields

Field Number	Description	Notes
1:3	Wall shear stress	Vector quantity, ordered τwallx, τwally, τwallz

Time Averaged Wall Shear Stress

• Header: wssbar
• solver.inp flag: Print Wall Fluxes: True and Print ybar: True

Fields

Field Number	Description	Notes
1:3	Average wall shear stress	Vector quantity, ordered τwallx, τwally, τwallz

Pressure Projection Vectors

• Header: pressure projection vectors
• solver.inp flag: placeholder