## Search found 41 matches

- Sat Dec 28, 2019 1:00 pm
- Forum: Rotor Aerodynamics
- Topic: Help about BEM and NREL's Phase VI
- Replies:
**41** - Views:
**10788**

### Re: Help about BEM and NREL's Phase VI

Yes Jason, i meant "phi" not 'x'. My main concern is how to deal with the case of a=1, and a' = -1; I understand your comments on Vx, Vy. Since I'm looking at the simple case of rigid blades, I'm using V_wind and r*Omega instead of Vx, Vy. Could you please tell me how are these exceptional...

- Thu Dec 26, 2019 1:38 pm
- Forum: Rotor Aerodynamics
- Topic: Help about BEM and NREL's Phase VI
- Replies:
**41** - Views:
**10788**

### Re: Help about BEM and NREL's Phase VI

Dear all,

Should the induction factors (a, a') and inflow angle (phi) obtained from FAST, satisfy the below equation always? I am using OpenFastV2.2.0.

[sin(phi) / (1 - a) ] - [ (V_wind/V_r)*cos(x) / (1 + a') ] = 0

where V_r = r*Omega_r;

Regards,

Kumara

Should the induction factors (a, a') and inflow angle (phi) obtained from FAST, satisfy the below equation always? I am using OpenFastV2.2.0.

[sin(phi) / (1 - a) ] - [ (V_wind/V_r)*cos(x) / (1 + a') ] = 0

where V_r = r*Omega_r;

Regards,

Kumara

- Fri Dec 20, 2019 3:31 am
- Forum: Rotor Aerodynamics
- Topic: Help about BEM and NREL's Phase VI
- Replies:
**41** - Views:
**10788**

### Re: Help about BEM and NREL's Phase VI

Dear Jason, I went through the source code ( inductionFactors subroutine, BEMTUncoupled module ) again. Now I understand the reason for defining 'a' twice (before and after the evaluation of residual). It is because Residual calculations (which are performed in later part of the code) require the va...

- Wed Dec 18, 2019 1:52 pm
- Forum: Rotor Aerodynamics
- Topic: Help about BEM and NREL's Phase VI
- Replies:
**41** - Views:
**10788**

### Re: Help about BEM and NREL's Phase VI

Dear Jason, I have one more question. In the source code corresponding to the propeller brake region, (Copied below) after setting IsValidSolution =.false, why to assign value to a? Because at another portion in the source copied below (with blue color text) a and a' are assigned as zeros. ? Please ...

- Wed Dec 18, 2019 12:31 pm
- Forum: Rotor Aerodynamics
- Topic: Help about BEM and NREL's Phase VI
- Replies:
**41** - Views:
**10788**

### Re: Help about BEM and NREL's Phase VI

Dear Jason. My apologies for not making the question clear enough. I am looking for the initialization value for the phi. I think I found the answer in the source code (in the colored text below). Thank you! !..............................................................................................

- Tue Dec 17, 2019 10:49 pm
- Forum: Rotor Aerodynamics
- Topic: Help about BEM and NREL's Phase VI
- Replies:
**41** - Views:
**10788**

### Re: Help about BEM and NREL's Phase VI

Dear Jason, Sorry, it is still not clear to me. Assume that blades and tower are rigid (no structural velocities), pitch angle=0, wind velocity =6 m/s (uniform), initial angular velocity of rotor = 2 rpm. Now, while calculating induction factors at time zero, the Phi_guess (for the very first iterat...

- Tue Dec 17, 2019 2:18 pm
- Forum: Rotor Aerodynamics
- Topic: Help about BEM and NREL's Phase VI
- Replies:
**41** - Views:
**10788**

### Re: Help about BEM and NREL's Phase VI

Dear Jason, I am currently using FASTV8.6, AeroDynV15.03. Now, I have downloaded OpenFASTV2.1.0 and going through the source code of AeroDyn in it. I see some differences compared to AeroDynV15.03. I could follow most of the details. If I understand it right, the starting point for the algorithm to ...

- Sun Dec 15, 2019 1:09 pm
- Forum: Rotor Aerodynamics
- Topic: Help about BEM and NREL's Phase VI
- Replies:
**41** - Views:
**10788**

### Re: Help about BEM and NREL's Phase VI

Dear Jason, I have implemented axial induction factor calculation in MATLAB as given in the paper "Ning, Andrew, et al. "Development and validation of a new blade element momentum skewed-wake model within AeroDyn." 33rd Wind Energy Symposium. 2015". I get good match for AxInd and...

- Tue Dec 10, 2019 11:35 am
- Forum: Controls
- Topic: Power coefficient/Aerodynamic torque
- Replies:
**17** - Views:
**978**

### Re: Power coefficient/Aerodynamic torque

Dear Jason,

Many thanks for your quick response. I'll do that.

Regards,

Kumara

Many thanks for your quick response. I'll do that.

Regards,

Kumara

- Tue Dec 10, 2019 11:16 am
- Forum: Controls
- Topic: Power coefficient/Aerodynamic torque
- Replies:
**17** - Views:
**978**

### Re: Power coefficient/Aerodynamic torque

Yes Jason. I am plotting AeroDyn output RtAeroCp. Yes, Induced velocity calculation is disabled in my simulation. I did not think about the fact that Betz limit is valid only when BEMT is used. Thanks for pointing that. Now I understand that exceeding Betz limit is sensible, but how is it possible t...

- Tue Dec 10, 2019 10:47 am
- Forum: Controls
- Topic: Power coefficient/Aerodynamic torque
- Replies:
**17** - Views:
**978**

### Re: Power coefficient/Aerodynamic torque

Dear Jason, I have performed simulation of WP1.5MW using FAST for the conditions specified below. I observe that Cp is greater than 1 as shown in figures. But it should be below Betz limit. Right? Could you please help me how to interpret this. Uniform wind speed: 6 m/s. Pitch controller: No pitch c...

- Sun Dec 08, 2019 12:05 am
- Forum: Structural Analysis
- Topic: Rotor Inertia computation
- Replies:
**4** - Views:
**256**

### Re: Rotor Inertia computation

Thanks, Jason. For the benefit of others, here is the formula for the p%RNodes: (Line 2432, ElastoDyn.F90 source file) p%RNodes = BladeMeshData(K)%RNodes - p%HubRad ! Radius to blade analysis nodes relative to root ( 0 < RNodes(:) < p%BldFlexL ) (Convert RNodes to be relative to the hub) Regards, Ku...

- Mon Dec 02, 2019 11:35 am
- Forum: Structural Analysis
- Topic: Rotor Inertia computation
- Replies:
**4** - Views:
**256**

### Re: Rotor Inertia computation

Dear Jason, Thanks for the clarification. It checks out now. For RNode definition, I looked at the picture (below) and mistook as the distance from the rotor axis. Bladelayout.JPG Instead I should have referred to the definition given in the later part of the FAST documentation as: RNodes These valu...

- Sun Dec 01, 2019 4:54 am
- Forum: Structural Analysis
- Topic: Rotor Inertia computation
- Replies:
**4** - Views:
**256**

### Rotor Inertia computation

Dear all, This question is regarding the rotor inertia reported in ElastoDyn summary file. And its computation. I have taken the below formula01 and 02 from the ElastoDyn Source Code. Variable K stands for the blade number; Formula01 : Blade Inertia Formula: (Line:4747) p%SecondMom(K) = p%SecondMom(...

- Fri Nov 29, 2019 1:46 pm
- Forum: Controls
- Topic: Blade pitch control
- Replies:
**20** - Views:
**7707**

### Re: Blade pitch control

Dear all, I am trying to implement a simple pitch controller in FAST using MATLAB (Simulink). However, I observe discrepancy in the pitch angle between MATLAB and FAST.out. Kindly note that here i am not using two different controllers in FAST and MATLAB. I am simply setting PCMode to 4 in servodyn....