Pressure Drop at different regions

philip.unglert · February 4, 2016, 10:49

Dear colleagues,

I have to determine the pressure loss of a geometry which consists of several pipe segments with different diameters (see sketch below).

sketch.jpg

I need to determine the pressure loss which is caused by each pipe segment (indicated by the different length l1, l2 and l3).

Below the sketch of the problem, I attached a "diagram" of the pressure drop that I would assume over the total length (l1+2+l3).

As I have not used StarCCM+ before (only ANSYS CFX and OpenFOAM), I have some questions:

How do I have to prepare the geometry in CAD (e.g. CATIA)? Is it possible to build one single part or do I have to import each pipe segment seperatly?
How do I have to pre-process my model in order to determine the pressure drop of each segment?

I would be great if you can give me some hints (or maybe a good tutorial). I would further be interessted in your experience / best practice guidelines regarding such type of problem.

Many thanks in advande,
Phil

fluid23 · February 4, 2016, 12:42

It looks like all you need to do is create two derived part > section > planes at l1 and l1 + l2 from your inlet. You will need to know the origin and normal at each location, but this shouldn't be an issue based on your sketch.

Next, create a series of mass flow averaged reports of pressure (total, static, whatever...) at the inlet, outlet and the two derived parts. Title them appropriately something like p0, p1, p2, and p3. Also define the units you want pressure reported in.

Finally, create three expression reports named dp1, dp2 and dp3. Make sure to define the dimensions as pressure and select the units to match your mass flow averaged pressure reports. Define each expression report as follows:
$p1Report-$p0Report
$p2Report-$p0Report
$p3Report-$p0Report

That should do it. Now if you want to setup a plot like you show within star-ccm, then you will need to create monitors from these dp reports and define an XY Plot. If you need help with this, let me know.

philip.unglert · February 4, 2016, 16:58

Dear MBdoneCFD,

many thanks for your quick reply!

As I understand your answer correct, the problem of determining seperate pressure losses can be reduced by generating several so called "derived" parts. Therefore, it is not neccesary to split the geometry directly in CAD, is this correct?

Does this procedere affect the mesh generation process? I would expect that the meshes of each "derived" part have to match each other...

Within the next days, I will try your procedere and give a feedback wether it worked or not.

Kind regards,
Phil

fluid23 · February 4, 2016, 17:29

No, this has nothing to do with mesh and is generated/regenerated after the mesh process. It will show the mesh that you slice through but does not affect the structure of the mesh. It is actually a handy way to check mesh through the domain at specific locations. You can also use these derived parts to look at flow distribution at the locations (i.e. plot scalars on them).

UdoUebel · February 9, 2016, 06:40

Quote:

Originally Posted by MBdonCFD

It looks like all you need to do is create two derived part > section > planes at l1 and l1 + l2 from your inlet. You will need to know the origin and normal at each location, but this shouldn't be an issue based on your sketch.

Next, create a series of mass flow averaged reports of pressure (total, static, whatever...) at the inlet, outlet and the two derived parts. Title them appropriately something like p0, p1, p2, and p3. Also define the units you want pressure reported in.

Finally, create three expression reports named dp1, dp2 and dp3. Make sure to define the dimensions as pressure and select the units to match your mass flow averaged pressure reports. Define each expression report as follows:
$p1Report-$p0Report
$p2Report-$p0Report
$p3Report-$p0Report

That should do it. Now if you want to setup a plot like you show within star-ccm, then you will need to create monitors from these dp reports and define an XY Plot. If you need help with this, let me know.

Thanks for this practice! Got almost the same challenge

Can you tell me for which reason it is necessary to know the origin & normal at each Location?

fluid23 · February 10, 2016, 10:10

That defines where your derived parts are at and what plane they lie in. For a simple axial pipe flow like you show it's fairly trivial. If your flow direction is [1, 0, 0] (from left to right in the sketch) and the origin is in the middle of the pipe all the way at the left end... your origin's and normals would be:

[L1,0,0] and [1,0,0]
[L1+L2,0,0] and [1,0,0].

This would create derived parts that have the shape of the cross-section at the locations that the diameter changes.

February 4, 2016, 10:49	Pressure Drop at different regions	#1
philip.unglert New Member Philip Unglert Join Date: Feb 2016 Posts: 2 Rep Power: 0	Dear colleagues, I have to determine the pressure loss of a geometry which consists of several pipe segments with different diameters (see sketch below). sketch.jpg I need to determine the pressure loss which is caused by each pipe segment (indicated by the different length l1, l2 and l3). Below the sketch of the problem, I attached a "diagram" of the pressure drop that I would assume over the total length (l1+2+l3). As I have not used StarCCM+ before (only ANSYS CFX and OpenFOAM), I have some questions: How do I have to prepare the geometry in CAD (e.g. CATIA)? Is it possible to build one single part or do I have to import each pipe segment seperatly? How do I have to pre-process my model in order to determine the pressure drop of each segment? I would be great if you can give me some hints (or maybe a good tutorial). I would further be interessted in your experience / best practice guidelines regarding such type of problem. Many thanks in advande, Phil Last edited by philip.unglert; February 4, 2016 at 16:59.

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February 4, 2016, 12:42		#2
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 18	It looks like all you need to do is create two derived part > section > planes at l1 and l1 + l2 from your inlet. You will need to know the origin and normal at each location, but this shouldn't be an issue based on your sketch. Next, create a series of mass flow averaged reports of pressure (total, static, whatever...) at the inlet, outlet and the two derived parts. Title them appropriately something like p0, p1, p2, and p3. Also define the units you want pressure reported in. Finally, create three expression reports named dp1, dp2 and dp3. Make sure to define the dimensions as pressure and select the units to match your mass flow averaged pressure reports. Define each expression report as follows: $p1Report-$p0Report $p2Report-$p0Report $p3Report-$p0Report That should do it. Now if you want to setup a plot like you show within star-ccm, then you will need to create monitors from these dp reports and define an XY Plot. If you need help with this, let me know.

February 4, 2016, 16:58		#3
philip.unglert New Member Philip Unglert Join Date: Feb 2016 Posts: 2 Rep Power: 0	Dear MBdoneCFD, many thanks for your quick reply! As I understand your answer correct, the problem of determining seperate pressure losses can be reduced by generating several so called "derived" parts. Therefore, it is not neccesary to split the geometry directly in CAD, is this correct? Does this procedere affect the mesh generation process? I would expect that the meshes of each "derived" part have to match each other... Within the next days, I will try your procedere and give a feedback wether it worked or not. Kind regards, Phil

February 4, 2016, 17:29		#4
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 18	No, this has nothing to do with mesh and is generated/regenerated after the mesh process. It will show the mesh that you slice through but does not affect the structure of the mesh. It is actually a handy way to check mesh through the domain at specific locations. You can also use these derived parts to look at flow distribution at the locations (i.e. plot scalars on them).

February 10, 2016, 10:10		#6
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 18	That defines where your derived parts are at and what plane they lie in. For a simple axial pipe flow like you show it's fairly trivial. If your flow direction is [1, 0, 0] (from left to right in the sketch) and the origin is in the middle of the pipe all the way at the left end... your origin's and normals would be: [L1,0,0] and [1,0,0] [L1+L2,0,0] and [1,0,0]. This would create derived parts that have the shape of the cross-section at the locations that the diameter changes.