Air Flow Analysis around a Wind Turbine

NightHawkRaven · January 29, 2014, 14:59

Hello,
I am from an Electrical Engineering background and am working on a wind turbine design project. I am looking to purchase a wind turbine for one of my commercial needs. But before I make a decision on the different types of wind turbines available in the market, I would like to simulate the airflow around a wind turbine and see how the output power and efficiency vary based on the different wind speeds.
I've been trying to gather some information from the different forums on this site, but I would be really happy if somebody could walk me through the basic procedure required to start off at this juncture. I mean, to be specific, how do I start off with the ANSYS Fluent software to simulate the airflow ? Since, I am not designing the wind turbine by myself but instead looking to purchase one, I don't have the CAD model of the turbine either. I've been listening to a lot of techniques such as "Moving Reference Frames", "Sliding Meshes", "Studying the Wind Turbine Wake by replacing the turbine array with Pressure Jump or Porous Media" etc., but I have no clue as to what each of these would mean ! I'm radically looking at the first basic step of the ANSYS Fluent simulation of a wind turbine - so please help me out on this issue.

P.S: Please make sure your response scales down to the most rudimentary level !

tcarrigan · January 29, 2014, 15:39

I wrote a journal article that describes a few of the things you mentioned. I also used FLUENT for the analysis. It's a VAWT, but the procedure is similar for a HAWT.

http://www.hindawi.com/isrn/renewabl...y/2012/528418/

NightHawkRaven · February 7, 2014, 15:21

Hey Travis,
Thanks for your publication ! But to be honest, I couldn't understand even a bit of whatever was in there ! As I said, I'm practically looking at the first basic step of ANSYS simulation., so please direct me to an even more basic tutorial.

I really appreciate your help in this regard !

stumpy · February 10, 2014, 17:15

You should start with some of the basic tutorials in the Fluent documentation, particularly those that deal with rotating reference frames. However, to be honest you could be wasting your time. Getting an accurate answer would take a lot of time and computational resources and reasonable amount of experience. You would need to make sure your mesh was sufficiently refined and resolves the boundary layer well and probably the wakes too. You might need to think about boundary layer transition effects. Would you include ground and tower effects, or just model a single blade, etc. You'd need a cluster and a bunch of parallel licenses to get any reasonable results. I would just look for something that is well proven and from a company that can stand behind its product. Just my 2 cents...

fluid23 · August 12, 2014, 17:18

NightHawkRaven,
This is probably too little too late, since you posted this 5 months ago. However, I would caution you against using CFD to help you select a wind turbine to purchase. Why, you ask?

1. You will need a massive amount of computational resources to accurately capture the aerodynamics of this problem.

2. If you are a beginner to CFD this problem is likely too complex to start with. People write entire PhD dissertations on only a small subset of the problem you are trying to solve. Your models will complex and large, the potential for human error in the setup is too great.

3. Every wind turbine manufactuer in the entire world provides power curves (Power Coefficient vs Tip Speed Ratio) for their products. This is how people decide to buy them vs another macine. This will give you the information you say you need.

4. If you are hell-bent on calculating these values for yourself, look into the free NREL Design Codes. The easiest is TurbSim, but I think that has been discontinued and replaced with AeroDyn. These are Blade Element Momentum (BEM) codes and are used to design blades and predict their performance and any number of off-design conditions including skewed wake, over speed, and so on. AeroDyn is a little complicated, but has options for modeling dynamic effects as well. Be advised, if you have little to no background in either 2D or 3D aerodynamics, you are going to struggle setting up your model. There are several good books on wind energy which give detailed formulations of BEM theory. I suggest you consult one before you attempt any BEM modeling. (For that matter, I suggest you read a basic CFD text book too before trying to jump into the deep end of the analysis pool).

5. The biggest problem I see with your approach to turbine selection is that you need to have the blade geometry in order to do either CFD or BEM analysis. In my experience, manufacturers rarely provide this data as it is highly proprietary. However, if you have airfoil distrbutions, airfoil aerodyanmic data, and chord/twist distributions you might be able to pull it off...

Good Luck! I am curious to know how your attempt in Feb turned out and if you do end up trying BEM analysis, I will be happy to answer any questions you have.

January 29, 2014, 14:59	Air Flow Analysis around a Wind Turbine	#1
NightHawkRaven New Member Join Date: Jan 2014 Location: Houston, Texas Posts: 6 Rep Power: 12	Hello, I am from an Electrical Engineering background and am working on a wind turbine design project. I am looking to purchase a wind turbine for one of my commercial needs. But before I make a decision on the different types of wind turbines available in the market, I would like to simulate the airflow around a wind turbine and see how the output power and efficiency vary based on the different wind speeds. I've been trying to gather some information from the different forums on this site, but I would be really happy if somebody could walk me through the basic procedure required to start off at this juncture. I mean, to be specific, how do I start off with the ANSYS Fluent software to simulate the airflow ? Since, I am not designing the wind turbine by myself but instead looking to purchase one, I don't have the CAD model of the turbine either. I've been listening to a lot of techniques such as "Moving Reference Frames", "Sliding Meshes", "Studying the Wind Turbine Wake by replacing the turbine array with Pressure Jump or Porous Media" etc., but I have no clue as to what each of these would mean ! I'm radically looking at the first basic step of the ANSYS Fluent simulation of a wind turbine - so please help me out on this issue. P.S: Please make sure your response scales down to the most rudimentary level !

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January 29, 2014, 15:39		#2
tcarrigan Senior Member Travis Carrigan Join Date: Jul 2010 Location: Arlington, TX Posts: 161 Rep Power: 15	I wrote a journal article that describes a few of the things you mentioned. I also used FLUENT for the analysis. It's a VAWT, but the procedure is similar for a HAWT. http://www.hindawi.com/isrn/renewabl...y/2012/528418/

February 7, 2014, 15:21		#3
NightHawkRaven New Member Join Date: Jan 2014 Location: Houston, Texas Posts: 6 Rep Power: 12	Hey Travis, Thanks for your publication ! But to be honest, I couldn't understand even a bit of whatever was in there ! As I said, I'm practically looking at the first basic step of ANSYS simulation., so please direct me to an even more basic tutorial. I really appreciate your help in this regard !

February 10, 2014, 17:15		#4
stumpy Senior Member Join Date: Apr 2009 Posts: 531 Rep Power: 21	You should start with some of the basic tutorials in the Fluent documentation, particularly those that deal with rotating reference frames. However, to be honest you could be wasting your time. Getting an accurate answer would take a lot of time and computational resources and reasonable amount of experience. You would need to make sure your mesh was sufficiently refined and resolves the boundary layer well and probably the wakes too. You might need to think about boundary layer transition effects. Would you include ground and tower effects, or just model a single blade, etc. You'd need a cluster and a bunch of parallel licenses to get any reasonable results. I would just look for something that is well proven and from a company that can stand behind its product. Just my 2 cents...

August 12, 2014, 17:18		#5
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	NightHawkRaven, This is probably too little too late, since you posted this 5 months ago. However, I would caution you against using CFD to help you select a wind turbine to purchase. Why, you ask? 1. You will need a massive amount of computational resources to accurately capture the aerodynamics of this problem. 2. If you are a beginner to CFD this problem is likely too complex to start with. People write entire PhD dissertations on only a small subset of the problem you are trying to solve. Your models will complex and large, the potential for human error in the setup is too great. 3. Every wind turbine manufactuer in the entire world provides power curves (Power Coefficient vs Tip Speed Ratio) for their products. This is how people decide to buy them vs another macine. This will give you the information you say you need. 4. If you are hell-bent on calculating these values for yourself, look into the free NREL Design Codes. The easiest is TurbSim, but I think that has been discontinued and replaced with AeroDyn. These are Blade Element Momentum (BEM) codes and are used to design blades and predict their performance and any number of off-design conditions including skewed wake, over speed, and so on. AeroDyn is a little complicated, but has options for modeling dynamic effects as well. Be advised, if you have little to no background in either 2D or 3D aerodynamics, you are going to struggle setting up your model. There are several good books on wind energy which give detailed formulations of BEM theory. I suggest you consult one before you attempt any BEM modeling. (For that matter, I suggest you read a basic CFD text book too before trying to jump into the deep end of the analysis pool). 5. The biggest problem I see with your approach to turbine selection is that you need to have the blade geometry in order to do either CFD or BEM analysis. In my experience, manufacturers rarely provide this data as it is highly proprietary. However, if you have airfoil distrbutions, airfoil aerodyanmic data, and chord/twist distributions you might be able to pull it off... Good Luck! I am curious to know how your attempt in Feb turned out and if you do end up trying BEM analysis, I will be happy to answer any questions you have.