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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 The information provided may be out of date.

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Free rotation of object in shear flow

Posted 2011年3月11日 GMT-5 17:43 Fluid & Heat Version 4.2 5 Replies

Thomas Hermans
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I'm trying to simulate a 2D object (propeller shaped) in a shear flow. I managed to let the propeller turn and move the liquid, but I want to have the opposite: the fluid should rotate the propeller. Any idea how to get "free rotation" of the propeller induced by the liquid flow?

THANKS A MILLION!!
5 Replies Last Post 2013年11月21日 GMT-5 18:20
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 2011年3月12日 GMT-5 04:56
Hi

the trick is to get the fluid pressure to generate a torque that rotates your device (I have often noticed difficulties to get it to "start to turn" but basically it works) I use an external ODE.

Hereafter are two views how I do it, with a global equation in V4.1.
Note there is formally an unit issue as torques are expressed in [N] and not [N*m] This is because (hope I'm correct) one should normally multiply by the depth of the device, I'm here in 2D so the depth is by default 1[m]

--
Good luck
Ivar
Hi the trick is to get the fluid pressure to generate a torque that rotates your device (I have often noticed difficulties to get it to "start to turn" but basically it works) I use an external ODE. Hereafter are two views how I do it, with a global equation in V4.1. Note there is formally an unit issue as torques are expressed in [N] and not [N*m] This is because (hope I'm correct) one should normally multiply by the depth of the device, I'm here in 2D so the depth is by default 1[m] -- Good luck Ivar
Waqqar Ahmed
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Posted: 1 decade ago 2011年11月17日 GMT-5 19:13
Hi Ivar,

Thanks for your insight. I am working on the simillar problem which is ellipsoid rotation with shear flow. I tried to compute the rotation of sphere using global equation as mentioned by you but I got the error " Failed to evealute variable Jacobian". I could not figure out where I went wrong. If possible, could you please send me the file with the program.
I will really appreciate that.
Hi Ivar, Thanks for your insight. I am working on the simillar problem which is ellipsoid rotation with shear flow. I tried to compute the rotation of sphere using global equation as mentioned by you but I got the error " Failed to evealute variable Jacobian". I could not figure out where I went wrong. If possible, could you please send me the file with the program. I will really appreciate that.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 2011年11月18日 GMT-5 03:54
Hi

from my understanding that means that your equation cannot be derived once, do you use a max() or min() or abs() or any bolean equations in your BC's ? these are the typical ones that give problems, or variables that COMSOL cannot evaluate

--
Good luck
Ivar
Hi from my understanding that means that your equation cannot be derived once, do you use a max() or min() or abs() or any bolean equations in your BC's ? these are the typical ones that give problems, or variables that COMSOL cannot evaluate -- Good luck Ivar
Navin Verma
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Posted: 1 decade ago 2012年4月7日 GMT-4 06:39
Hi Thomas,

Could you complete this simulation?
would you please attach final simulation?

I am facing similar problem.

Thanking you.
Hi Thomas, Could you complete this simulation? would you please attach final simulation? I am facing similar problem. Thanking you.
Tsung-Hsing Hsu
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Posted: 1 decade ago 2013年11月21日 GMT-5 18:20
Hi Ivar,

From the 2nd pic that you post, what are the parameters of "rpmt" and "Izz"? How could we find it in equation view? I'm having the same problem regarding to the rotation in the model. Actually, it should be easier to use fluid structure interaction model, but I totally have no idea how to set the rotating wall. Would you please help me on that? Thank you for your help.

Kevin
Hi Ivar, From the 2nd pic that you post, what are the parameters of "rpmt" and "Izz"? How could we find it in equation view? I'm having the same problem regarding to the rotation in the model. Actually, it should be easier to use fluid structure interaction model, but I totally have no idea how to set the rotating wall. Would you please help me on that? Thank you for your help. Kevin

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