[J. Pan]

Originally Posted by sharonyue

Update,

Oh, time flies...

I think I figure it out, put it simple, if we want calculate the torque on the blade, this is quite simple, please see the output below:

forces forces output:
    sum of forces:
        pressure : (70.3478 2.53417 -0.129928)
        viscous  : (-8.35929e-07 -3.77215e-07 -9.01343e-07)
        porous   : (0 0 0)
    sum of moments:
        pressure : (-0.01138 -0.00344619 -9.2415)
        viscous  : (-8.14101e-08 -1.81033e-08 7.56807e-08)
        porous   : (0 0 0)

U can neglect all the other things if u just need the value of torque. The value on the red is torque. From this torque we can use this to calculate power.

power = 2 * 3.14 * rps * torque

By this, I got almost the rite power with experiment.

Dear sharonyue,

I am confused that why your torque is minus. In my case (2D Savonius rotor), I got the moment value in every time step. And I calculated the average value of all output values of Z component, which is also a negative value. Can you help me to explain the reason of minus value please? I am stuck for a long time. My controlDict is shown as below:

functions
{
forces
{
type forces;
libs ("libforces.so");
writeControl timeStep;
writeInterval 1;
patches (dragblade_1 dragblade_2);
porosity no;
pRef 0;
rho rhoInf;
log true;
rhoInf 1.225;
CofR (0 0 0);
pitchAxis (0 0 -1);
}
}

Best, J.Pan

[J. Pan]

Originally Posted by sharonyue

Update,

Oh, time flies...

I think I figure it out, put it simple, if we want calculate the torque on the blade, this is quite simple, please see the output below:

forces forces output:
    sum of forces:
        pressure : (70.3478 2.53417 -0.129928)
        viscous  : (-8.35929e-07 -3.77215e-07 -9.01343e-07)
        porous   : (0 0 0)
    sum of moments:
        pressure : (-0.01138 -0.00344619 -9.2415)
        viscous  : (-8.14101e-08 -1.81033e-08 7.56807e-08)
        porous   : (0 0 0)

U can neglect all the other things if u just need the value of torque. The value on the red is torque. From this torque we can use this to calculate power.

power = 2 * 3.14 * rps * torque

By this, I got almost the rite power with experiment.

Dear sharon,

May I ask you to explain why the torque is minus please? I am confused about that.

Best, J.Pan