CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

VAWT - average torque = 0, and TSR very low for 1dof system

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   November 8, 2019, 13:57
Default VAWT - average torque = 0, and TSR very low for 1dof system
  #1
New Member
 
Joachim Hansen
Join Date: Nov 2019
Posts: 1
Rep Power: 0
toftegaard23 is on a distinguished road
I am simulating a H-rotor VAWT (Vertical Axis Wind Turbine) with three blades using ANSYS Fluent, and I have set up the rotor to allow free rotation around its centre axis (1dof system). My inlet wind speed is 15 m/s, Iíve made ANSYS calculate the moment for each timestep and I use NACA0018 as the aerofoil-design type. After approximately 5 seconds (transient study with the blades standing still to begin with), the rotor has reached a steady state, and from the motion history written, I can see the angular velocity corresponds to a tip speed ratio of 0.06. Furthermore, the average of my moment values is very close to zero, which makes sense in that the rotor is not accelerating Ė it rotates with a constant speed. However, power is calculated as the product of the average torque and angular velocity, but since the average torque is zero, then I donít produce any power, which shouldnít be the case?

I have also tried to set the rotor to rotate with a constant angular velocity that corresponds to a TSR = 4. This gives me torque-values that are negative for a positive angular velocity, hence the power is negative. This means the rotor needs to receive energy to maintain its rotational velocity, which again is contradictory to how a wind turbine works.

One thing, I am not sure about is how you can include the resistance by the generator, since this depends on the magnetic flux etc.? One of my professors said that because I do not include frictional resistance in the simulation, then the simulation can either go to infinity, since there is nothing slowing it down, or it can reach a steady state, which is what has happened to mine. I just donít understand why I got the second option? And why I get the solutions and numbers that I get?

Appreciate your time and any input can be a massive help.
Attached Images
File Type: jpg moment_curve.jpg (43.1 KB, 0 views)
toftegaard23 is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
VAWT Sliding Mesh - Negative Torque Pervispasco OpenFOAM Running, Solving & CFD 0 August 5, 2018 10:59
Issue with Negative Torque in 2D VAWT MRF Simulation fall3n FLUENT 0 December 22, 2017 19:50
Low Coefficient of Moment for VAWT, 2D, TOlsen FLUENT 0 October 29, 2016 12:11
low and negative torque eng.nassim FLUENT 0 September 24, 2011 17:02


All times are GMT -4. The time now is 17:03.