View source for Convective Thermal Flow

[[Category:benchmark]]
[[Category:Oberwolfach]]
[[Category:linear]]
[[Category:time invariant]]
[[Category:first differential order]]
[[Category:MIMO]]
[[Category:sparse]]

{{Infobox
|Title           = Convective Thermal Flow
|Benchmark ID    = 
* ctfChipCoolingv0_n20082m1q5
* ctfChipCoolingv01_n20082m1q5
* ctfFlowMeterv0_n9669m1q5
* ctfFlowMeterv05_n9669m1q5
|Category        = oberwolfach
|System-Class    = LTI-FOS
|nstates         = 
* 20082
* 20082
* 9669
* 9669
|ninputs         = 1
|noutputs        = 5
|nparameters     = 0
|components      = A, B, C, E
|License         = NA
|Creator         = C. Moosmann, E.B. Rudnyi, A. Greiner, J.G. Korvink
|Editor          = 
* [[User:Himpe]]
|Zenodo-link     = NA
}}

==Description: Convective Thermal Flow Problems==
<figure id="fig1">[[File:Convection1.jpg|490px|thumb|right|Figure 1: Convective heat flow example: 2D anemometer model]]</figure>
<figure id="fig2">[[File:Convection2.jpg|490px|thumb|right|Figure 2: Convective heat flow example: 3D cooling structure]]</figure>

Many thermal problems require simulation of heat exchange between a solid body and a fluid flow.
The most elaborate approach to this problem is [[wikipedia:Computational_fluid_dynamics|computational fluid dynamics]] (CFD).
However, CFD is computationally expensive.
A popular solution is to exclude the flow completely from the computational domain and to use convection boundary conditions for the solid model.
However, caution has to be taken to select the [[wikipedia:Heat_transfer_coefficient|film coefficient]].

An intermediate level is to include a flow region with a given velocity profile that adds convective transport to the model.
Compared to convection boundary conditions this approach has the advantage that the film coefficient does not need to be specified and that information about the heat profile in the flow can be obtained.
A drawback of the method is the greatly increased number of elements needed to perform a physically valid simulation because the solution accuracy when employing upwind finite element schemes depends on the element size.
While this problem still is linear, due to the forced convection, the conductivity matrix changes from a symmetric matrix to an un-symmetric one.
So this problem type can be used as a benchmark for problems containing un-symmetric matrices.

Two different designs are tested: a 2D model of an [[Anemometer|anemometer]]-like structure mainly consisting of a tube and a small heat source (Fig.&nbsp;1) <ref name="ernst2001"/>.
The solid model has been generated and meshed in [http://www.ansys.com ANSYS].
Triangular <tt>PLANE55</tt> elements have been used for meshing and discretizing by the finite element method, resulting in 19282 elements and 9710 nodes.
The second design is a 3D model of a chip cooled by forced convection (Fig.&nbsp;2) <ref name="harper1997"/>.
In this case, the tetrahedral element type <tt>SOLID70</tt> was used, resulting in 107989 elements and 20542 nodes.
Since the implementation of the convective term in ANSYS does not allow defining the fluid speed on a per-element basis but on a per-region one, the flow profile has to be approximated by piece-wise step functions.
The approximation used for these benchmarks is shown in Fig.&nbsp;1.

The Dirichlet boundary conditions are applied to the original system.
In both models, the reference temperature is set to <math>300 \, \text{K}</math>, and Dirichlet boundary conditions as well as initial conditions are set to <math>0</math> with respect to the reference.
The specified Dirichlet boundary conditions are in both cases the inlet of the fluid and the outer faces of the solids. Matrices are supplied for the symmetric case (fluid speed is zero; no convection), and the non-symmetric case (with forced convection).
Table&#160;1 shows the output nodes specified for the two benchmarks, Table&#160;2 links the filenames according to the different cases.

Practically, only a few nodes are considered quantities of interest.
Hence, a small subset of five nodes is selected as output nodes,
which are filtered from the discretized state by a linear transformation.

==Origin==

This benchmark is part of the '''Oberwolfach Benchmark Collection'''<ref name="korvink2005"/>; No. 38867, see <ref name="moosmann2005"/>.

==Data==

Matrices are in the [http://math.nist.gov/MatrixMarket/ Matrix Market] format.
The matrix name is used as an extension of the matrix file.
<tt>*.C.names</tt> contains a list of output names written consecutively.
The system matrices have been extracted from ANSYS models by means of [http://portal.uni-freiburg.de/imteksimulation/downloads/mor4fem mor4fem].

{| class="wikitable" style="margin: auto;"
|+ style="caption-side:bottom;"|''Table 1: Output nodes for the two models.''
|-
!Model
!Number
!Code
!Comment
|-
|Flow Meter
|1
|out1
|outlet position
|-
|
|2
|out2
|outlet position
|-
|
|3
|SenL
|left sensor position
|-
|
|4
|Heater
|within the heater
|-
|
|5
|SenR
|right sensor position
|-
|Cooling Structure
|1
|out1
|outlet position
|-
|
|2
|out2
|outlet position
|-
|
|3
|out3
|outlet position
|-
|
|4
|out4
|outlet position
|-
|
|5
|Heater
|within the heater
|}
 

{| class="wikitable" style="margin: auto;"
|+ style="caption-side:bottom;"|''Table 2: Provided files.''
|-
!Model
!Fluid Speed (m/s)
!Link
!Size
|-
|Flow Meter
|<math>0</math>
|[https://csc.mpi-magdeburg.mpg.de/mpcsc/MORWIKI/Oberwolfach/Convection-dim1e4-flow_meter_model_v0.tgz Convection-dim1e4-flow_meter_model_v0.tgz]
|649.4 kB
|-
|
|<math>0.5</math>
|[https://csc.mpi-magdeburg.mpg.de/mpcsc/MORWIKI/Oberwolfach/Convection-dim1e4-flow_meter_model_v0.5.tgz Convection-dim1e4-flow_meter_model_v0.5.tgz]
|757.8 kB
|-
|Cooling Structure
|<math>0</math>
|[https://csc.mpi-magdeburg.mpg.de/mpcsc/MORWIKI/Oberwolfach/Convection-dim1e4-chip_cooling_model_v0.tgz Convection-dim1e4-chip_cooling_model_v0.tgz]
|3.9 MB
|-
|
|<math>0.1</math>
|[https://csc.mpi-magdeburg.mpg.de/mpcsc/MORWIKI/Oberwolfach/Convection-dim1e4-chip_cooling_model_v0.1.tgz Convection-dim1e4-chip_cooling_model_v0.1.tgz]
|4.0 MB
|}

Further information on the models can be found in <ref name="moosmann2004"/>,
where model reduction by means of the [[wikipedia:Arnoldi_iteration|Arnoldi algorithm]] is also presented.

==Dimensions==

System structure:

:<math>
\begin{align}
  E \dot{x}(t) &= A x(t) + B u(t) \\
  y(t) &= C x(t)
\end{align}
</math>

System dimensions:

<math>E \in \mathbb{R}^{n \times n}</math>,
<math>A \in \mathbb{R}^{n \times n}</math>,
<math>B \in \mathbb{R}^{n \times 1}</math>,
<math>C \in \mathbb{R}^{5 \times n}</math>.

System variants:

<tt>flow_v0</tt>: <math>n = 9669</math>,
<tt>flow_v0.5</tt>: <math>n = 9669</math>,
<tt>chip_v0</tt>: <math>n = 20082</math>,
<tt>chip_v0.1</tt>: <math>n = 20082</math>.

==Citation==

To cite this benchmark, use the following references:

* For the benchmark itself and its data:
::The MORwiki Community, '''Convective Thermal Flow'''. MORwiki - Model Order Reduction Wiki, 2018. http://modelreduction.org/index.php/Convective_Thermal_Flow

 @MISC{morwiki_convection,
   author =       <nowiki>{{The MORwiki Community}}</nowiki>,
   title =        {Convective Thermal Flow},
   howpublished = {{MORwiki} -- Model Order Reduction Wiki},
   url =          <nowiki>{https://modelreduction.org/morwiki/Convection}</nowiki>,
   year =         {2018}
 }

* For the background on the benchmark:

 @INPROCEEDINGS{morMooRGetal04,
   author =       <nowiki>{C. Moosmann, E.B. Rudnyi, A. Greiner, J.G. Korvink}</nowiki>,
   title =        {Model Order Reduction for Linear Convective Thermal Flow},
   booktitle =    {Proceedings of 10th International Workshops on THERMal INvestigations of ICs and Systems},
   year =         {2004},
   url =          <nowiki>{http://modelreduction.com/doc/papers/moosmann04THERMINIC.pdf}</nowiki>
 }

==References==

<references>

<ref name="korvink2005"> J.G. Korvink, E.B. Rudnyi, <span class="plainlinks">[https://doi.org/10.1007/3-540-27909-1_11 Oberwolfach Benchmark Collection]</span>, Dimension Reduction of Large-Scale Systems, Lecture Notes in Computational Science and Engineering, vol 45: 311--315, 2005.</ref>

<ref name="ernst2001">H. Ernst, <span class="plainlinks">[https://freidok.uni-freiburg.de/data/201 High-Resolution Thermal Measurements in Fluids]</span>, PhD thesis, University of Freiburg, Germany, 2001.</ref>

<ref name="harper1997">C.A. Harper, <span class="plainlinks">[https://doi.org/10.1036/0071430482 Electronic packaging and interconnection handbook]</span>, New York McGraw- Hill, USA, 1997</ref>

<ref name="moosmann2004">C. Moosmann, E.B. Rudnyi, A. Greiner, J.G. Korvink, <span class="plainlinks">[http://modelreduction.com/doc/papers/moosmann04THERMINIC.pdf Model Order Reduction for Linear Convective Thermal Flow]</span>, Proceedings of 10th International Workshops on THERMal INvestigations of ICs and Systems, THERMINIC2004, Sophia Antipolis, France, 2004.</ref>

<ref name="moosmann2005">C. Moosmann, A. Greiner, <span class="plainlinks">[https://doi.org/10.1007/3-540-27909-1_16 Convective Thermal Flow Problems]</span>, In: Dimension Reduction of Large-Scale Systems. Springer, Berlin, Heidelberg. Lecture Notes in Computational Science and Engineering, vol 45: 341--343, 2005.</ref>

</references>