Numerically strange cp value about windpowerplants HOT 16 CLOSED

from windpowerplants.

Can you reproduce it?

from windpowerplants.

I see there is a problem; I am working on a solution...

from windpowerplants.

OK, thanks for the feedback.

from windpowerplants.

I suppose the problem is solved in master. It took a couple investigations and changes in the library to make everything working. Please check whether the simulations now work fine with SimulationX.

from windpowerplants.

It still gives a floating-point overflow when computing cp.

turbineData_c1=0.50000000000000000;
turbineData_c2=116.00000000000000;
turbineData_c3=0.40000000000000002;
turbineData_c4=5.0000000000000000;
turbineData_c5=21.000000000000000;
turbineData_c6=0.00000000000000000;
beta=0.00000000000000000;
lambda=-0.10171009365613741;
lambda1=1/(1/(0.088999999999999996+lambda)- 0.035000000000000003/(1+beta*beta*beta)); /* -0.012704442043449671 */
cp=turbineData_c6*lambda1+turbineData_c1*(turbineData_c2/lambda1- (turbineData_c3*beta+turbineData_c4))*exp( -(turbineData_c5/lambda1));

The exponent -(turbineData_c5/lambda1) is about 1653 here which results in magnitude of 10E+717 for the natural power. Such a number cannot be represented by IEEE double precision floating-point arithmetic.

from windpowerplants.

Any news on this issue?

from windpowerplants.

I am sorry, but I have absolutely no time to work on this issue at the moment. However, I am very much interested in overcoming the problems. I somehow guess that I will have time by mid next week to work on this issue again.

from windpowerplants.

I restricted lambda to positive values which solves the issue on my opinion. This is also the correct physical solution since cp should not become negative at all.

I checked in the solution in master. Please check and drop me a note.

from windpowerplants.

Cannot find the corresponding commit.

from windpowerplants.

Sorry, I did not commit properly. The changes should now be in.

from windpowerplants.

Should it better be this way?

Real lambdaLimited(min=0) "Positive tip speed ratio";
/* ... */
lambdaLimited = if noEvent(lambda<0) then 0 else lambda;

from windpowerplants.

I incorporated your suggestion in master.

from windpowerplants.

Thanks. Can hopefully test it tomorrow.

from windpowerplants.

Fix confirmed.

@AlexMagdanz FYI.

from windpowerplants.

Created version v0.9.5 incorporating this fix.

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