Vertical axis wind turbine

DrBidden · November 28, 2012, 19:32

I am using a local rotating region around the impellor and axis which is transverse to the wind flow. The question is how large to make the diameter of the rotating region. There will be an error at the interface between wind direction and rotation. I thought that by making the diameter of the rr large then the error is further away from the impellor. However all that happens is you get a distinct rotating object ie the region and when you look at the velocity contours there is no continuity through the interface of the rr. I understand that if we were dealing with an axial (conventional) wind turbine then it is easier to define the rr. Any advice would be welcome.

Boris_M · December 18, 2012, 06:52

Hi DrBidden,

Did I understand you correct?
You have an transverse fan where you want to have the fluid blown through it perpendicular to its rotating axis? So entering the RR on one side of the circumfernece and leaving it on the other side of the circumference?

This is a limitation of the RR and therefore not possible as the cicumverential velocity is averaged. This means that if we consider the flow going in x-direction through the fan it enters the fan with a relative velocity of for example +10m/s and exits it with -10m/s. This means it will average to 0m/s.

I hope this helps,
Boris

DrBidden · December 19, 2012, 20:03

Thanks for your reply. I am aware of the circumferential averaging hence the question about how best to set up the rotating region, in order to minimise error as much as possible. I currantly have aRR which is in the shape of an annulus so it only contains the vanes, and not the central region of the rotor. The alternative is to use a Global rotating option, but this has other problems associated with it.

Boris_M · December 21, 2012, 04:45

The problem with every RR is that is has cirumferential surfaces which are averaging the flow, no matter if anular or a full cylinder. There is no minimizing it for such cross flow, tangential or transverse fans. If you cannot use it as global rotating it will not give you correct results. I'm sorry.

Boris

DrBidden · December 21, 2012, 21:50

Thanks for your reply. I will try to use the Global Rotation instead. Thanks for you help

November 28, 2012, 19:32	Vertical axis wind turbine	#1
DrBidden New Member colin Join Date: Dec 2011 Posts: 10 Rep Power: 14	I am using a local rotating region around the impellor and axis which is transverse to the wind flow. The question is how large to make the diameter of the rotating region. There will be an error at the interface between wind direction and rotation. I thought that by making the diameter of the rr large then the error is further away from the impellor. However all that happens is you get a distinct rotating object ie the region and when you look at the velocity contours there is no continuity through the interface of the rr. I understand that if we were dealing with an axial (conventional) wind turbine then it is easier to define the rr. Any advice would be welcome.

December 19, 2012, 20:03	Hi Boris	#3
DrBidden New Member colin Join Date: Dec 2011 Posts: 10 Rep Power: 14	Thanks for your reply. I am aware of the circumferential averaging hence the question about how best to set up the rotating region, in order to minimise error as much as possible. I currantly have aRR which is in the shape of an annulus so it only contains the vanes, and not the central region of the rotor. The alternative is to use a Global rotating option, but this has other problems associated with it.

December 21, 2012, 21:50	Hi Boris	#5
DrBidden New Member colin Join Date: Dec 2011 Posts: 10 Rep Power: 14	Thanks for your reply. I will try to use the Global Rotation instead. Thanks for you help

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December 18, 2012, 06:52		#2
Boris_M Disabled Join Date: Jul 2009 Posts: 616 Rep Power: 24	Hi DrBidden, Did I understand you correct? You have an transverse fan where you want to have the fluid blown through it perpendicular to its rotating axis? So entering the RR on one side of the circumfernece and leaving it on the other side of the circumference? This is a limitation of the RR and therefore not possible as the cicumverential velocity is averaged. This means that if we consider the flow going in x-direction through the fan it enters the fan with a relative velocity of for example +10m/s and exits it with -10m/s. This means it will average to 0m/s. I hope this helps, Boris

December 21, 2012, 04:45		#4
Boris_M Disabled Join Date: Jul 2009 Posts: 616 Rep Power: 24	The problem with every RR is that is has cirumferential surfaces which are averaging the flow, no matter if anular or a full cylinder. There is no minimizing it for such cross flow, tangential or transverse fans. If you cannot use it as global rotating it will not give you correct results. I'm sorry. Boris