Blade Tip-brake Model in OpenFAST

Hi Everyone,

I’ld like to implement a rotating tip brake for a variable speed stall-regulated small wind turbine in OpenFAST v2.1.

Roughly speaking, the tip-brake model looks like this https://isaacbrana.files.wordpress.com/2010/07/passive-control-of-tip-blade-using-screw-on-tip-shaft-and-spring1.jpg . A centrifugal force is pre-defined to activate the rotor tip brake. This centrifugal force causes the blade tip segment to rotate 90° in high wind conditions especially when the rotor exceeds its rated rotational speed.

According to Guide to Changes in FAST v8 and this discussion [url]http://forums.nrel.gov/t/blade-tip-brake-in-fast/1893/1], I understand that the tip-vane type of tip brake was developed only in FAST v7 and was not further developed in OpenFAST. Is this the one described in section 3.1 of this document, Investigation of Aerodynamic Braking Devices for Wind Turbine Applications"? In the case of the rotating tip-brake model, what would be the most viable way to implement it in AeroDyn or ServoDyn? Does anyone have an experience with this kind of blade tip-brake model in FAST v8 or OpenFAST ? I would greatly appreciate any suggestion.

Best regards,
Moe Moe

Dear Moe Moe,

NREL has still not been funded to implement a tip brake into FAST v8 or OpenFAST. I’ll let others on the forum comment if they’ve developed something.

The tip-brake model of FAST v7 and older was a very simple model that could likely be tailored to model the braking of any type of tip-brake device, at least at a global level. A more sophisticated tip-brake model is likely warranted if you want to model the details of a specific tip-brake device.

Best regards,

Dear Jason,

Thank you very much for your quick reply. I really appreciate it.

It helps me better understand the tip-brake model developed in FAST v7.

Best regards,
Moe Moe

Hi Everyone,

I compiled the original OpenFAST v2.1 and the compilation was successfully completed after making some changes described in the following link https://github.com/OpenFAST/openfast/pull/288/commits/b20de94608ef06eda30d69bc532435c9a8037940.

Then, I tried to migrate blade tip-brake model from FAST v7 into OpenFAST v2.1 to run the simulation of a variable speed stall-regulated small wind turbine, following the instructions stated in NTWC Programmer’s Handbook and making certain changes to the source codes according to the following link https://github.com/OpenFAST/openfast/commits/dev?after=b05e73f04419370e5aefb3fb7c3365e9d0008cca+34. I’ve also made some changes in ElastoDyn Module ( ElastoDyn.f90, ElastoDyn_Registery.txt), ServoDyn Module (ServoDyn.f90, ServoDyn_Registery.txt) and FAST (FAST_Solver, FAST_Subs.f90 and FAST_Registery.txt) for implementing blade tip brake parameters in OpenFAST. Here, it is assumed that the tip brakes are controlled by setting a rotor speed at which each brake is deployed. Please see the changes to the source codes in the following document. I recompile the modified OpenFAST and unfortunately end up with the following errors (please see the attachment Errors_while_Compiling_OpenFAST_with_tipbrakemodel.docx).

I’ve been grappling with this problem since a couple of weeks and couldn’t fix them up until now. Does someone have an idea where the source of the problem could be and how I can fix them? I would greatly appreciate any suggestion.

Best regards,
Moe Moe
Errors_while_Compiling_OpenFAST_with_tipbrakemodel.docx (20.5 KB)
Changes in OpenFAST for blade tip-brake Model_MMA.docx (18.3 KB)

Dear Moe Moe,

I don’t have the time to review your source code and errors myself right now, but I would recommend that you repost your question on OpenFAST issues: github.com/OpenFAST/openfast/issues. Since the transition to OpenFAST, OpenFAST issues has become the go-to place to discuss source code and compiling-related Q&A, whereas this forum tends to focus on FAST / OpenFAST usage Q&A. There are many more OpenFAST developers who check OpenFAST issues than this forum.

Best regards,

Dear Jason,

Thank you very much for your recommendation for an appropriate place to ask this question. I’ll repost it on OpenFAST issues.

Best regards,
Moe Moe