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HISTORY - Time history flowfield variable tracking (block)

Structured Grids

   VARIABLE [M] [p] [T] [u] [v] [w] [radius] [DeltaP] [x] [y] [z] \
            [rho] [rho*u] [rho*v] ...
   REGION nzn ibeg iend jbeg jend kbeg kend
   REGION nzn [NODE | CELL] num

For unsteady flow problems, the HISTORY keyword block allows the user to track the temporal evolution of variables at discrete specified points. The specified flow quantities are written to a common time history (.cth) file every f iterations. Upon completion of a time history run, the auxiliary program thplt may be used to analyze the data and/or to create a GENPLOT file that may then be plotted using CFPOST. [Because of changes to the format of the .cth file, the timplt utility used to analyze .cth files created by WIND 5.51 and earlier will not work with .cth files created by the current Wind-US code.] The .cth file contains reference and scaling data. Thus, when thplt is used to create a GENPLOT file, the time history variables will be dimensional.

For the results to be strictly valid, all zones must run with the same time step and with one iteration per cycle. However, in recognition that this is not always feasible, this capability can be used with only the stipulation that the zone(s) in which temporal evolution information is desired be run with a constant time step.

The .cth file itself does not support direct I/O. Therefore, when Wind-US is being run in parallel mode, each individual processor maintains the requested time history for its zones, but calls the master process to update the .cth file whenever the flow (.cfl) file is updated, and whenever the time history memory buffer is filled. This forces the .cth file to be consistent with the .cfl file.

It should be noted that although time history files are commonly referred to as .cth files, Wind-US automatically appends the current date and time to the end of the file name, using the format mm-dd-yyhhhmmm. As an example, for a case run using an input data (.dat) file named config3.dat, the resulting time history file might be config3.cth.08-22-07h22m19, indicating that it was created at on Aug. 22, 2007, at 10:19 PM. Restarting a calculation will thus result in multiple time history files, one for each individual run. The time history post-processing tool thplt can read multiple .cth files to analyze the data and/or create a single GENPLOT file combining the different time intervals.

The various elements of the HISTORY keyword block are defined as follows:


Defines the beginning of the HISTORY block.

VARIABLE [M] [p] [T] [u] [v] [w] [radius] [DeltaP] [x] [y] [z] \
         [rho] [rho*u] [rho*v] ...

Specifies the variables to be recorded. At least one must be specified, and the maximum allowed is fifteen. Note that variable names are case-sensitive. The first eight variables shown above are defined as follows:

    M   Mach number
p Static pressure
T Static temperature
u Velocity in the x direction
v Velocity in the y direction
w Velocity in the z direction
radius Distance from a specified reference point to the location of a shock front. See the section Front Tracking Mode for details.
DeltaP Monotone pressure rise across the shock front. See the section Front Tracking Mode for details.

In addition to the variables listed above, any variable in the q array may be specified. These of course depend on the equations being solved. The possible q variables are listed below, in groups, along with an indication of when they are available.

    Name   Definition   When Used

---Navier-Stokes equations
rho Static density Always
rho*u Momentum in the x direction
rho*v Momentum in the y direction
rho*w Momentum in the z direction
rho*e0 Total energy
---Auxiliary parameters
beta Effective specific heat ratio Always
Z Compressibility factor
a Speed of sound
kappa Thermal conductivity
dt Time step
mul Laminar viscosity coefficient Viscous flows
mut Turbulent viscosity coefficient
---Turbulence equations
anut Eddy viscosity Baldwin-Barth and Spalart-Allmaras turbulence models
k Turbulent kinetic energy SST and k-ε turbulence models
omega Specific dissipation rate SST turbulence model
epsilon Turbulent dissipation k-ε turbulence models
---Chemistry equations
species Mass fraction of species, where species is the species name defined in the chemistry data file (also see the CHEMISTRY keyword block) Non-reacting chemistry
rho*species Finite-rate reacting chemistry
shf Specific heat of formation Chemistry
---Navier-Stokes equations in rotating frame
rho*ur Momentum in the x direction in a rotating reference frame (rho*u, etc., are in the inertial frame) Rotating reference frame
rho*vr Momentum in the y direction in a rotating reference frame
rho*wr Momentum in the z direction in a rotating reference frame
rho*e0r Total energy in a rotating reference frame
---MFD equations
Bx, By, Bz Magnetic field components in the x, y, and z directions MFD flows
Ex, Ey, Ez Electric field components in the x, y, and z directions
Jx, Jy, Jz Current density components in the x, y, and z directions
Lx, Ly, Lz Lorentz force components in the x, y, and z directions
sigma Conductivity
voltage Voltage


Specifies the number of solver iterations between output of time history information. The default is to write to the .cth file every 10 iterations.

REGION nzn ibeg iend jbeg jend kbeg kend
REGION nzn [NODE | CELL] num

Defines the discrete locations where temporal information will be sampled in zone nzn. The different formats correspond to a structured zone range, and a particular node or cell in an unstructured node-based or cell-based scheme. [Note, though, that Wind-US does not yet support the use of the HISTORY keyword with unstructured grids.]

Except for the special-purpose variables radius and DeltaP, in a structured grid time history data will be recorded at each point in the domain defined by the indices (ibeg,jbeg,kbeg) to (iend,jend,kend). The variables radius and DeltaP are intended for use in tracking the location of a shock wave. In this case, the REGION parameters are defined differently. See the section Front Tracking Mode for details.

Multiple REGION lines may be used to specify multiple sampling regions, in the same zone, or different zones. Grid sequencing is supported for structured grids, but there is presently no other way (except multiple REGION lines) to spatially sub-sample a region.


Defines the end of the HISTORY block.

See Also: TEST 142

Front Tracking Mode

For structured grids, a special mode exists that can be useful for tracking the motion of shock waves. If the region is specified as:

   REGION nzn i0 idir j0 jdir k0 kdir
where one of idir, jdir, kdir is ±1 and the other two are zero, then front tracking mode is active in zone nzn.

Beginning at the point (i0,j0,k0), the solution is sampled to the end of the zone in the specified direction, looking for the maximum change in pressure across a cell. This location is then used as the "probe location" to output the specified variables. In this context, the radius variable represents the distance of this point from the point (i0,j0,k0). Note that this is probably the only time that a time history variable of x, y, or z makes sense, as they can be used to more precisely specify the location of the detected front.

To provide an indication of the evolution of the shock strength, the variable DeltaP can be used. When this variable is specified, the search is continued from the detected front location to the end of the zone, in the specified search direction, and the maximum monotone pressure change is recorded.

Example 1

The following use of the HISTORY block will create a time history file containing the static pressure at the points (17,1,1), (17,11,5), and (9,11,7) in zones 1, 2, and 3, respectively. Values will be written to the file every ten iterations.

      Variable p
      Region 1 17 17  1  1 1 1
      Region 2 17 17 11 11 5 5
      Region 3  9  9 11 11 7 7

Example 2

In the following example, the Mach number and pressure will be recorded in zone 5, for the grid points (i,j,k) = (7-16,22-24,19). Values will be written to the file every five iterations.

      Variable M p
      Frequency 5
      Region 5 7 16 22 24 19 19

Example 3

In this example, the position and strength of a shock wave will be tracked in the +i direction in zone 4. The point (1,52,20) will be used as the reference point, and values will be recorded every 20 iterations.

      Variable radius x DeltaP
      Frequency 20
      Region 4 1 1 52 0 20 0

Last updated 31 Oct 2011