View source for FAQ/Solution procedure

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[[Category:FAQSection]]

== FAQ Section [[faqnumber::4]]: [[faqname::Solution procedure]] ==
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[[faqdescription::Manipulating the solution procedure by non-programming means]]
=== How does one turn off the dimensional checking? ===

Dimensional checking is one of the cool features in OpenFOAM that helps to develop solvers that do something physically meaningful. Therefore: don't do this if not absolutely necessary.

To switch it off at run-time:
<pre>dimensionSet 0;</pre>
in the global {{tt|controlDict}} file or in the local one. A few example paths:
* In OpenFOAM 1.1: <tt>OpenFOAM-1.1/.OpenFOAM-1.1/controlDict</tt>
* In OpenFOAM 1.5 and newer: <tt>OpenFOAM-1.5/etc/controlDict</tt>

For more details on how to set these options, see section [[HowTo_debugging#Getting built-in feedback from OpenFOAM|Getting built-in feedback from OpenFOAM]] at [[HowTo_debugging]].

A more controlled way is to use the <tt>dimensions()</tt>-method to set the dimension of the  <tt>volXXXField</tt> in question to the desired dimension.

(source: [https://www.cfd-online.com/Forums/openfoam-solving/60598-how-does-one-turn-off-dimensional-checking.html How does one turn off the dimensional checking])

=== Is there a way to switch between single and double precision? ===

; For Version 1.2 and older: Only by editing <tt>src/OpenFOAM/primitives/scalar/scalar.H</tt> and recompiling OpenFOAM. But why would you want to do that (except for memory issues)?
(source: [http://openfoam.cfd-online.com/forum/messages/1/591.html])

; For Version 1.3 and newer: Recompile OpenFOAM with ''single-precision'' enabled, by setting the environment variable {{tt|WM_PRECISION_OPTION}} to {{tt|SP}}. For more details, see section [[Installation/Working_with_the_Shell#OpenFOAM_Environment_Variables|OpenFOAM Environment Variables]] at [[Installation/Working_with_the_Shell]].

=== Why doesn't my solver have any residuals for the velocity equations? ===
# Edit the file {{tt|system/fvSolution}}.
# Look inside the {{tt|SIMPLE}}, {{tt|PISO}} or {{tt|PIMPLE}} block that you have configured for the solver you're using.
# You will find that you probably have {{tt|momentumPredictor}} set to {{tt|no}}.
Faqdescription	Manipulating the solution procedure by non-programming means +
Faqname	Solution procedure +
Faqnumber	4 +