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IDProjectCategoryView StatusDate SubmittedLast Update
0001451OpenFOAMBugpublic2014-12-04 15:452014-12-28 14:38
Reporterjoegi Assigned Tohenry  
PrioritynormalSeverityminorReproducibilityalways
Status closedResolutionno change required 
PlatformlinuxOSopensuseOS Version12.3
Summary0001451: Pressure stair-step behaviour using rhopimplefoam
DescriptionHi,

I don't know if this properly classifies as a bug, but I am having an strange stair-step behavior on the pressure when using rhopimplefoam.

The case consists of a simple straight pipe (Poiseuille case, so we have an analytical solution). I am computing the solution using icoFoam, pimpleFoam, and rhoPimpleFoam for the same mesh, physical properties, and same boundary conditions. The peak velocity is about 2.8 m/s, so I expect rhoPimpleFoam to yield to the same results as those of the incompressible solvers. While the velocity is pretty much the same, the pressure along the pipe axis of rhoPimpleFoam shows a stair-step (wiggles) behavior, whereas the pressure reported by the incompressible solvers has a smooth behavior (as expected and desired). At this point, I wonder if you have seen this behavior.

I have used many different numerical schemes and I always see the same behavior. Using finer meshes did not yield to better results.

By the way, I see the same behavior using the Heat transfer and buoyancy-driven flows solvers.
Steps To ReproduceRun:

Go to rp5:

blockMesh -dict system/blockMeshDict

rhoPimpleFoam

sample -latestTime


Then go to pimple:

blockMesh

pimpleFoam

sample -latestTime


Then compare the solutions for both cases (pressure).
TagsNo tags attached.

Activities

joegi

2014-12-04 15:45

viewer  

pimple.tar.gz (6,504 bytes)

joegi

2014-12-04 15:50

viewer  

f1.png (32,669 bytes)   
f1.png (32,669 bytes)   

joegi

2014-12-04 15:51

viewer  

f2.png (10,177 bytes)   
f2.png (10,177 bytes)   

joegi

2014-12-04 15:51

viewer  

f3.png (15,211 bytes)   
f3.png (15,211 bytes)   

joegi

2014-12-04 16:39

viewer  

f4.png (16,290 bytes)   
f4.png (16,290 bytes)   

joegi

2014-12-04 16:40

viewer   ~0003298

The last figure is a comparison between fluent and openfoam. Using same BC, IC and numerical method.

dhora

2014-12-14 22:10

reporter   ~0003318

Try to increase the write precision ;-)

Issue History

Date Modified Username Field Change
2014-12-04 15:45 joegi New Issue
2014-12-04 15:45 joegi File Added: pimple.tar.gz
2014-12-04 15:50 joegi File Added: f1.png
2014-12-04 15:51 joegi File Added: f2.png
2014-12-04 15:51 joegi File Added: f3.png
2014-12-04 16:39 joegi File Added: f4.png
2014-12-04 16:40 joegi Note Added: 0003298
2014-12-14 22:10 dhora Note Added: 0003318
2014-12-28 14:38 henry Status new => closed
2014-12-28 14:38 henry Assigned To => henry
2014-12-28 14:38 henry Resolution open => no change required