# How to specify curved piston motion

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June 2, 2020, 05:54
How to specify curved piston motion
#1
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Abdullah Jamil
Join Date: Jun 2020
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I want to do cold flow cfd analysis of a curved cylinder engine. The piston oscillates in the curved cylinder. In ICE (Fluent) module, we specify cylinder linear faces, but it is for linear piston motion. How can I specify the cylinder curved face or curved path for the piston to follow with each crank angle? Kindly have a look at the attached image of the curved cylinder engine.
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 June 2, 2020, 06:05 Curved Piston #2 Senior Member     Vinerm Join Date: Jun 2009 Location: Nederland Posts: 2,946 Blog Entries: 1 Rep Power: 35 You can do this, however, the system is physically useless if the piston is rigid. How do you expect a rigid face, the crown of the piston, to cover two multiple distances? The distance to be traveled by the sides close to higher curvature is much less than those close to lower curvature. So, the piston will move, but the stroke cannot be long enough to be useful. __________________ Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.

June 2, 2020, 06:13
#3
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Abdullah Jamil
Join Date: Jun 2020
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Quote:
 Originally Posted by vinerm You can do this, however, the system is physically useless if the piston is rigid. How do you expect a rigid face, the crown of the piston, to cover two multiple distances? The distance to be traveled by the sides close to higher curvature is much less than those close to lower curvature. So, the piston will move, but the stroke cannot be long enough to be useful.
Its alright, the motion is same as that of a toroidal engine. If one side has small displacement, the other side has a big one. So thats not an issue. Have a look at the image below:

But I dont know how to apply this condition in Fluent for piston motion. Please let me know about it. Thanks in advance!

 June 2, 2020, 07:20 Motion #4 Senior Member     Vinerm Join Date: Jun 2009 Location: Nederland Posts: 2,946 Blog Entries: 1 Rep Power: 35 This does make sense. As far as motion is concerned, you just need to give angular motion and not linear one. If you use Dynamic Mesh, then piston will be a rigid body with C.G. at the center of rotation and motion will be angular one without any linear motion. __________________ Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.

 July 9, 2020, 01:17 Define Dynamic Mesh for Piston #5 New Member   Abdullah Jamil Join Date: Jun 2020 Posts: 13 Rep Power: 5 Kind regards. Last edited by geniusjimmy92; August 4, 2020 at 09:41.

 Tags cfd, cylinder, engine, fluent, piston