cfd_values

Synopsis

The User Macro cfd_values computes derived CFD field quantities from base values in the PLOT3D format (density, momentum, and stagnation).

Input Ports

Name Type Description
&in Node_Data[] Input CFD NodeData multiblock array

Parameters

The following lists all of the parameters found in the parameter block CFDValsParams, which are accessed by the module CFDValsNodeData and the UI Macro CFDValsUI.

Name Type Description UI Control
gamma double gamma constant (default 1.4) Gamma
gas_constant double gas constant (default 1) Gas Constant
do_energy boolean Toggle energy calculation Energy
do_pres boolean Toggle pressure calulation Pressure
do_enthalpy boolean Toggle enthalpy calculation Enthalpy
do_mach boolean Toggle mach number calculation Mach Number
do_temp boolean Toggle temperature calculation Temperature
tot_pres boolean Toggle total pressure calculation Total Pressure
tot_temp boolean Toggle total temperature calculation Total Temperature

Output Ports

Name Type Description
out Mesh+ Node_Data [] Output CFD Field array

Description

The module CFDValsNodeData computes derived CFD field quantities from base values in the PLOT3D format. It inputs an array of Structured Fields (5-vector data at nodes)

  • density
  • x-momentum
  • y-momentum
  • z-momentum
  • stagnation

This module takes input in the form produced by the Read PLOT3D module, with an array of fields (multiblock) with 5 scalar components. Based on the toggle parameters, this module computes numerically derived quantities, usefull for flow visualization.

Two scalar parameters, Gamma and Gas Constant may be set in the user interface.

The field that cfd values receives from read plot3D has the following 5 values: density, X momentum, Y momentum, Z momentum, and stagnation.

From these 5 values cfd values computes 7 new values:

  • energy
  • pressure
  • enthalpy
  • mach number
  • temperature
  • total pressure
  • total temp

The gamma constant and the gas constant are user controllable parameters, and the following variables are defined: 

       d = density
       xm = x momentum
       ym = y momentum
       zm = z momentum
       st = stagnation

The equations used to derive the new values are as follows: 

       energy = stag / d
       pressure = (gamma - 1)(stag - ((0.5/d)(xm^2+ym^2+zm^2))
       enthalpy = (gamma/(gamma - 1))pressure/d
       mach number (M) = square_root(xm^2+ym^2+zm^2)
                         ---------------------------------------
                         (d * square_root(gamma * pressure /d ))
       temperature(T) = pressure / (d * gas constant)
       total pressure = pressure * exp(log(x) * gamma/(gamma - 1)
              where x = 1 - 0.5(gamma - 1) M * M
       total temperature = T(1 + (0.5*(gamma - 1) M * M

Note that, in calculating the 7 derived quantities, cfd values uses the same assumptions about the non-dimensionality, or normalization, of data that the National Aeronautics and Space Administration's PLOT3D, and the read plot3D module themselves use.

The min/max range of data is set on all blocks for consistancy. The module will compile and run in the user or express process.

The reader is written in an "omethod" style in C, with a multi-block (arrays of fields) output data structure. The DVswitch module can be used to select just one of the blocks for visualization with Main-Page modules, otherwise use the ARR modules for multiblock processing.

The low level code module takes a parameter block with default values as input. It only operates on Node_Data, and ignores the mesh. The user interface is in a separate macro and can be removed or replaced.

Input Ports

&in

The input Node_Data array.

Parameters

gamma

Specifies the gamma value to be used in the equations. A floating point value between 1 and 5, which determines the value of the constant. The formulas assume an ideal gas with a constant ratio of specific heats. The default value is 1.4.

gas_constant

Specifies the gas constant value to be used in the equations. A floating point value between 0 and 5, which determines the value of the gas constant. The default value is 1.

do_energy

Toggle the calculation of the energy.

do_pres

Toggle the calculation of the pressure.

do_enthalpy

Toggle the calculation of the enthalpy.

do_mach

Toggle the calculation of mach number.

do_temp

Toggle the calculation of the temperature.

do_totpres

Toggle the calculation of the total pressure.

do_tottemp

Toggle the calculation of the total temperature.

Output Ports

out

Output field array with modified Node_Data.

Utility Macros

The Functional Macro CFDVals and the UI Macro CFDValsUI are used in this User Macro cfd_values. The functional macro contains an instance of the low-level module CFDValsNodeData.

Example

An example application CFDValsEg is provided.

Files

iac_proj/cfdvals/cfdvmacs.v contains the cfd_values User Macro, the CFDVals Functional Macro, the CFDValsUI UI Macro, and the example application CFDValsEg V definitions.

Other Notes

The CFDValsMacs library inherits its process. As this library contains no procedural code, the process is not important. The low-level CFDValsNodeData module, executes under the process specified in its library, not the process defined in the high-level library.

Authors

Ian Curington, AVS Inc. (March 97)

Modifications

Paul G. Lever

Contact

International AVS Centre
Manchester Visualization Centre
Manchester Computing
University of Manchester
Oxford Road
Manchester
United Kingdom
M13 9PL

See Also

CFDValsParams, CFDValsUI, CFDVals and CFDValsNodeData.