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<th nowrap width="1%" height="32">P0008</th>
<th nowrap width="98%">CFDVals</th>
<th nowrap width="1%">27th November 1998</th>
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<p><b>Author:</b> Ian Curington
<b>Version:</b> 1.0
<b>Path:</b> iac_proj/cfdvals/</p>
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<h1>CFDValsNodeData</h1>
<h3>Synopsis</h3>
<p>
The module CFDValsNodeData computes derived CFD field quantities from base values in the PLOT3D format (density, momentum, and stagnation).
</p>
<p>
<hr>
<pre>
module CFDValsNodeData <src_file="cfdvals.c"> {
Node_Data+read+notify+req &in <NEportLevels={2,0}> [];
CFDValsParams &CFDValsParams <NEportLevels={2,0}>;
double+read+notify+req gamma => CFDValsParams.gamma;
double+read+notify+req gas_constant => CFDValsParams.gas_constant;
int+read+notify+req do_energy => CFDValsParams.do_energy;
int+read+notify+req do_pres => CFDValsParams.do_pres;
int+read+notify+req do_enthalpy => CFDValsParams.do_enthalpy;
int+read+notify+req do_mach => CFDValsParams.do_mach;
int+read+notify+req do_temp => CFDValsParams.do_temp;
int+read+notify+req do_totpres => CFDValsParams.do_totpres;
int+read+notify+req do_tottemp => CFDValsParams.do_tottemp;
int nblocks => array_size(in);
Node_Data+write+nonotify out[nblocks];
CFDVals_comb_mesh_and_data CFDVals_comb_mesh_and_data[nblocks] {
int index => index_of(CFDVals_comb_mesh_and_data);
in_mesh => <-.in[index];
in_nd => <-.out[index];
};
mlink+OPort2 fields => CFDVals_comb_mesh_and_data.out;
omethod+notify_val+notify_inst update<status=1> = "cfd_values_update";
};
</pre>
<hr>
</p>
<h3>Description</h3>
<p>
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)
<ul>
<li>density
<li>x-momentum
<li>y-momentum
<li>z-momentum
<li>stagnation
</ul>
<p>
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.
</p>
<p>
Two scalar parameters, Gamma and Gas Constant may be set
in the user interface.
</p>
<p>
The field that cfd values receives from read plot3D has the following
5 values: density, X momentum, Y momentum, Z momentum, and stagnation.
</p>
<p>
From these 5 values cfd values computes 7 new values:
<ul>
<li>energy
<li>pressure
<li>enthalpy
<li>mach number
<li>temperature
<li>total pressure
<li>total temp
</ul>
<p>
The gamma constant and the gas constant are user controllable parameters, and the following variables are defined:
</p>
<pre>
d = density
xm = x momentum
ym = y momentum
zm = z momentum
st = stagnation
</pre>
<p>
The equations used to derive the <i>new</i> values are as follows:
</p>
<pre>
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
</pre>
<p>
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.
</p>
<p>
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.
</p>
<p>
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.
</p>
<p>
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.
</p>
<h3>Inputs</h3>
<p>
<i><b>&in</b></i>
</p>
<p>
The input Node_Data array.
</p>
<p>
<i><b>&CFDValsParams</b></i>
</p>
<p>
Reference to the parameter block, which contains real instances of:
</p>
<p>
<i><b>gamma</b></i>
</p>
<p>
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.
</p>
<p>
<i><b>gas_constant</b></i>
</p>
<p>
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.
</p>
<p>
<i><b>do_energy</b></i>
</p>
<p>
Toggle the calculation of the energy.
</p>
<p>
<i><b>do_pres</b></i>
</p>
<p>
Toggle the calculation of the pressure.
</p>
<p>
<i><b>do_enthalpy</b></i>
</p>
<p>
Toggle the calculation of the enthalpy.
</p>
<p>
<i><b>do_mach</b></i>
</p>
<p>
Toggle the calculation of mach number.
</p>
<p>
<i><b>do_temp</b></i>
</p>
<p>
Toggle the calculation of the temperature.
</p>
<p>
<i><b>do_totpres</b></i>
</p>
<p>
Toggle the calculation of the total pressure.
</p>
<p>
<i><b>do_tottemp</b></i>
</p>
<p>
Toggle the calculation of the total temperature.
</p>
<h3>Outputs</h3>
<p>
<i><b>fields</b></i>
</p>
<p>
Output field array with modified Node_Data.
</p>
<h3>Utility Macros</h3>
<p>
The CFDValsNodeData module is used in conjunction with the CFDVals Functional Macro and the CFDValsUI UI Macro to form the User Macro <a href="doc_umac.shtml" target="_top">cfd_values</a>.
</p>
<h3>Example</h3>
<p>
An example application CFDValsEg is provided.
</p>
<h3>Files</h3>
<p>
<I>iac_proj/cfdvals/cfdvmods.v</I> contains the CFDValsParams group and the CFDValsNodeData module V definitions.
</p>
<h3>Other Notes</h3>
<p>
The low-level CFDValsMods library containing the module CFDValsNodeData does not specify a process. By default the <tt>express</tt> process will be used.
</p>
<h3>Authors</h3>
<p>
<pre>
Ian Curington, AVS Inc. (March 97)
</pre>
</p>
<h3>Modifications</h3>
<p>
<pre>
Paul G. Lever
</pre>
</p>
<h3>Contact</h3>
<p>
<pre>
International AVS Centre
Manchester Visualization Centre
Manchester Computing
University of Manchester
Oxford Road
Manchester
United Kingdom
M13 9PL
</pre>
</p>
<h3>See Also</h3>
<p>
CFDValsParams, CFDValsUI, <a href="doc_umac.shtml" target="_top">cfd_values</a>.
</p>
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