CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Pre-Processing

OpenFoam - DynamicMesh SphericalAngularDamper value

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

LinkBack Thread Tools Search this Thread Display Modes
Old   August 16, 2021, 12:09
Default OpenFoam - DynamicMesh SphericalAngularDamper value
New Member
Join Date: Mar 2021
Posts: 8
Rep Power: 2
BasG is on a distinguished road
Hi all,

At the moment I am modelling the efficiency for a hydraulic turbine in OpenFOAM. The generated theoretical power results from the product of angular velocity and torque around the turbine axis.

For this purpose I use the dynamic mesh solver sixDoFRigidBodyMotion. From a sensitivity analysis it follows that the sphericalAngularDamper restraint has a large influence on the modelled angular velocity and torque (see attachment).

This parameter has the unit [Nms/rad] and represents friction against angular motion. It acts in the opposite direction with respect to the angular motion.

The parameter is defined as follows:

    //- Some dumping functions
            //- Nms/rad
            //  Acts against motion as friction
            sixDoFRigidBodyMotionRestraint  sphericalAngularDamper;
            coeff 500;
My question is: how do I estimate the value of the coefficient for the turbine? If I know from the manufacturer that the overall efficiŽncy of this turbine is about 90%, can I transfer this efficiency into a coefficient for anuglar friction?

I hope to hear from you!

Attached Images
File Type: png CFD-Turbine_Angvel_Torque.png (143.3 KB, 10 views)
BasG is offline   Reply With Quote

Old   October 4, 2021, 07:04
Default repl:
New Member
Join Date: Mar 2021
Posts: 8
Rep Power: 2
BasG is on a distinguished road
I discovered that there are multiple ways to find optimum operational conditions for a turbine in order to yield maximum production. The first is by running multiple simulations with a forced rotation for various rotational speeds (under a constant flow velocity). The second one is to apply a model with free rotation (and a fixed flow velocity) whilst varying the angular friction coefficient until one finds optimum conditions. Hence, the angular friction coefficient is not a term one knows on beforehand, but one must search for an optimum value that leads to maximum production of the turbine.
BasG is offline   Reply With Quote


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
OpenFoam - DynamicMesh SphericalAngularDamper value BasG OpenFOAM Pre-Processing 0 August 16, 2021 10:49
Frequently Asked Questions about Installing OpenFOAM wyldckat OpenFOAM Installation 1 June 24, 2021 21:34
UNIGE February 13th-17th - 2107. OpenFOAM advaced training days joegi.geo OpenFOAM Announcements from Other Sources 0 October 1, 2016 20:20
Suggestion for a new sub-forum at OpenFOAM's Forum wyldckat Site Help, Feedback & Discussions 20 October 28, 2014 10:04
64bitrhel5 OF installation instructions mirko OpenFOAM Installation 2 August 12, 2008 19:07

All times are GMT -4. The time now is 09:59.