Search found 41 matches

by KumaraRaja.Eedara
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...
by KumaraRaja.Eedara
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
by KumaraRaja.Eedara
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...
by KumaraRaja.Eedara
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 ...
by KumaraRaja.Eedara
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! !..............................................................................................
by KumaraRaja.Eedara
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...
by KumaraRaja.Eedara
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 ...
by KumaraRaja.Eedara
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...
by KumaraRaja.Eedara
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
by KumaraRaja.Eedara
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...
by KumaraRaja.Eedara
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...
by KumaraRaja.Eedara
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...
by KumaraRaja.Eedara
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...
by KumaraRaja.Eedara
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(...
by KumaraRaja.Eedara
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....

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