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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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No change in laminar flow simulation results even after changing material properties like Dynamic viscosity and Density.

Posted 2013年11月22日 GMT-5 01:05 Fluid & Heat Version 4.3b 4 Replies

Vishal Prajapati
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Hi,

I have been doing very straight-forward and simple laminar flow simulations in a chamber. I have observed that flow simulation results don't change if I add and use another fluid with different dynamic viscosity and density. I tried varying the viscosity values but I couldn't notice any change in velocity gradients. I don't fully trust my results because of this reason.
Also, I would not be able to run these flow simulations if I don't mention at least dynamic viscosity and density of the fluid.

Thank you for having a look.

Best,
Vishal
4 Replies Last Post 2016年3月9日 GMT-5 06:32
Mikael Noerregaard Nielsen
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Posted: 1 decade ago 2013年11月26日 GMT-5 02:57
Hey Vishal

Is it possible for you to upload your model, so I/we can have a look at it?

Best regards

Mikael
Hey Vishal Is it possible for you to upload your model, so I/we can have a look at it? Best regards Mikael
Vishal Prajapati
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Posted: 1 decade ago 2013年11月26日 GMT-5 04:48
Hej Mikael,

Thanks. I am afraid to say that having trouble attaching the model file, I always get the "File size error" message. My minimum file size is 5.93 MB. It would be great if you could suggest me some way to make it available to you. Thanks.

Anyway, after delving into basics of Fluid Mechanics I realized that fluid velocity would hardly depend on the viscosity of the fluid for a given flow rate and geometry. My model is pretty simple: Its a chamber of 20 x 20 x 2 mm^3 dimensions connected to 4 channels of hydraulic diameter of 0.8 mm on all four sides. I am simulating 90 degree flow configuration. Please find the image attached for better understanding.

Currently, my sole problem is that my velocity prediction in different parts of chamber using simulation doesn't really match with my Particle Image Velocimetry (PIV) experiments. I am confident that my PIV results are accurate and reproducible which are cross-checked using alternate methods. There is approximately on an average 76% deviation of COMSOL results from PIV results. The velocity values given by COMSOL are much lesser than that given by PIV.

Moreover, the velocity values don't change much with the change in Mesh size. I understand without model file nothing can be said and done much.

Tak,
Vishal
Hej Mikael, Thanks. I am afraid to say that having trouble attaching the model file, I always get the "File size error" message. My minimum file size is 5.93 MB. It would be great if you could suggest me some way to make it available to you. Thanks. Anyway, after delving into basics of Fluid Mechanics I realized that fluid velocity would hardly depend on the viscosity of the fluid for a given flow rate and geometry. My model is pretty simple: Its a chamber of 20 x 20 x 2 mm^3 dimensions connected to 4 channels of hydraulic diameter of 0.8 mm on all four sides. I am simulating 90 degree flow configuration. Please find the image attached for better understanding. Currently, my sole problem is that my velocity prediction in different parts of chamber using simulation doesn't really match with my Particle Image Velocimetry (PIV) experiments. I am confident that my PIV results are accurate and reproducible which are cross-checked using alternate methods. There is approximately on an average 76% deviation of COMSOL results from PIV results. The velocity values given by COMSOL are much lesser than that given by PIV. Moreover, the velocity values don't change much with the change in Mesh size. I understand without model file nothing can be said and done much. Tak, Vishal
Vishal Prajapati
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Posted: 1 decade ago 2013年11月26日 GMT-5 20:24
Hi Mikael,

I have deleted mesh, solutions and study (Stationary) to make the file size very small. Thanks a lot for the suggestion, it worked. Please find the file attached here.

Thank you.
Best,
Vishal
Hi Mikael, I have deleted mesh, solutions and study (Stationary) to make the file size very small. Thanks a lot for the suggestion, it worked. Please find the file attached here. Thank you. Best, Vishal
Aisha Ambreen
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Posted: 9 years ago 2016年3月9日 GMT-5 06:32
Hi Vishal,

Did you figure out the answer for this question? Why are simulation results same even after changing the viscosity of fluid?

Aisha
Hi Vishal, Did you figure out the answer for this question? Why are simulation results same even after changing the viscosity of fluid? Aisha

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