WTPERF requests for enhancement?

Hi everybody,
it is, I guess, a small request that I have, but I would appreciate it very much. If I am wrong, please correct me.

I would like to be able to do parametric studies with WTPERF, using the InputTSR (Tip Speed Ratio) flag, not only on Cp (Power Coefficient), but also on the Thrust and on the Flap-Bending Moment.

At the moment, the output quantities of the parametric study are:

  • Rotor Power
  • Power Coefficient
  • Rotor Torque
  • Flap Bending moment
  • Rotor Thrust

The only adimensional quantity is the Power Coefficient. Activating the InputTSR Flag I get a TWO-Dimensional matrix, where I can interpolate from any given couple of data: [TSR, Pitch]. The Omega is (correctly) ignored.

I would like to be able to do the same for Thrust and Flap Bending Moment (being dimensional, at the moment they depend on THREE values: [omega (rpm), wind speed, Pitch].

This should mean adding two possible outputs:

  • Coefficient of thrust
  • something like a Coefficient of Flap Moment
    both will be function only of [TSR, Pitch]

Well, I hope I explained myself…

Best regards

Addressing Claudio’s points:

The number of iteration parameters is completely independent of what output parameters you want to generate. You can output thrust as a function of pitch and TSR.

I had previously decided to add Ct and Cq to the output list. I guess I can add Cf(?) to that list. And again, they can be functions of wind speed, pitch and rpm or TSR and pitch.

I’m sorry, but these changes will not happen this year. If I do any more code development this year, it will be on AeroDyn. I would suggest that you can convert the dimensional quantities to non-dimensional ones with a simple spreadsheet until I have a chance to update the code.


Marshall, then I will turn my request for enhancements in a request for help :slight_smile:

This was actually my original intention: but, unless I am making something wrong, the results DO depend on the omega. I will try to make an example of my results. The end of my input file is something like:
----- I/O Settings -----------------------------------------------------------
True TabDel: Make output tab-delimited (fixed-width otherwise).
True KFact: Output dimensional parameters in K (e.g., kN instead on N)
False WriteBED: Write out blade element data to “.bed”?
True InputTSR: Input speeds as TSRs?
“mps” SpdUnits: Wind-speed units (mps, fps, mph), ignored if InputTSR=True.
----- Combined-Case Analysis -------------------------------------------------
0 NumCases: Number of cases to run. Enter zero for parametric analysis.
WS or TSR RotSpd Pitch Remove following block of lines if NumCases is zero.
----- Parametric Analysis (Ignored if NumCases > 0 ) -------------------------
3 ParRow: Row parameter (1-rpm, 2-pitch, 3-tsr/speed).
2 ParCol: Column parameter (1-rpm, 2-pitch, 3-tsr/speed).
1 ParTab: Table parameter (1-rpm, 2-pitch, 3-tsr/speed).
False OutPwr: Request output of rotor power?
True OutCp: Request output of Cp?
False OutTrq: Request output of shaft torque?
False OutFlp: Request output of flap bending moment?
True OutThr: Request output of rotor thrust?
-5, 45, 0.3125 [2]-PitSt, PitEnd, PitDel: First, last, delta blade pitch (deg).
150, 150, 0.1 [1]-OmgSt, OmgEnd, OmgDel: First, last, delta rotor speed (rpm) [Should have no effect if InputTSR=True].
1, 21, 0.125 [3]-TSRSt, TSREnd, TSRDel: First, last, delta TSR (adimensional)

Now, the results for CP and Thrust should be independent of the value of Omega that I supply, or am I wrong?
Now, fact is: if I change the omega line to:
the CP matrix remains unchanged, but the Thrust changes (pretty much).

Again, this is now a request for help :slight_smile:

thanks a lot
and best regards


You are correct that the value of dimensional outputs will vary with rotor speed for a given TSR. Obviously, the wind speed will change. However, you can still leave the rotor speed at a constant value while varying TSR and pitch to produce a single 2-D matrix. You can then use a simple spreadsheet to convert the dimensional data to non-dimensional form. The resulting values will be independent of rotor speed.

Would you like some help with the spreadsheet?


Thanks, Marshall,
no I don’t… now I finally understood what you mean!. I have been trying with the Thrust, and it seems to work. In my understanding, I have to compute, for every line of the matrix, a formula derived from the substitution of the wind speed with its expression in terms of TSR and Omega

WindSpeed = Omega*RotorRadius/TSR

(taking care of the units!).

If I am not wrong, for example, I came out with the following:


If I do this, apart from very small numerical errors, the result IS independent of Omega. And I have a 2-D Matrix function of (TSR,Pitch).

Thansk again for your advice!
Best Regards
C. Pedrazzi