# Comparison of FAST.Farm and SOWFA **URL:** \ **Category:** Computer-Aided Engineering Software Tools\ **Created:** [October 10, 2024, 5:18pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684 "2024-10-10T17:18:28Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Ipsita.Mishra](https://avatars.discourse-cdn.com/v4/letter/i/5daacb/32.png) [@Ipsita.Mishra](https://forums.nlr.gov/u/Ipsita.Mishra)\ **Post date:** [October 10, 2024, 5:18pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/1 "2024-10-10T17:18:28Z")
Hello Dr. Jason, I am a new user of FAST.Farm and have run a few r-test cases available on GitHub. Now, I’m looking for published papers that use FAST.Farm to simulate wake steering in small wind farms with two or three turbines so that I can create the results and match them with the document. So far, I haven’t found any papers focusing on small wind farm wake steering with FAST.Farm, but I’ve come across several studies using SOWFA for this purpose. I’m interested in replicating the results from the paper " [Simulation comparison of wake mitigation control strategies for a two‐turbine case ([wiley.com](http://wiley.com))]"([https://onlinelibrary.wiley.com/doi/epdf/10.1002/we.1810](https://onlinelibrary.wiley.com/doi/epdf/10.1002/we.1810)). I have a few questions: 1. If I generate the test set-up given in the paper and run it in FAST.Farm, will the results of the turbine power production and DELs of the turbine components be the same as those obtained from SOWFA? 2. What additional changes should be made in the FAST.Farm, so that I can get comparable results with SOWFA 3. Do you have any relevant papers which I can run using FAST.Farm for 2-3 turbine cases so that it will help in my research as a benchmark case. Regards Ipsita Mishra ---
**Author:** ![Jason.Jonkman](https://dub1.discourse-cdn.com/nrel/user_avatar/forums.nlr.gov/jason.jonkman/32/3086_2.png) [@Jason.Jonkman](https://forums.nlr.gov/u/Jason.Jonkman)\ **Post date:** [October 10, 2024, 5:50pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/2 "2024-10-10T17:50:45Z")
Dear @Ipsita.Mishra, Here are my responses: 1. We ran the exact case from the paper you cite with the curled wake formulation of FAST.Farm and published the results in the following paper: [https://onlinelibrary.wiley.com/doi/full/10.1002/we.2785](https://onlinelibrary.wiley.com/doi/full/10.1002/we.2785). 2. Hopefully FAST.Farm will generate results close to SOWFA using DEFAULT wake parameters in FAST.Farm. But you most likely get improved results from FAST.Farm if you calibrate the wake parameters of FAST.Farm to the specific conditions (specific turbine, specific inflow) of the SOWFA simulations. 3. Other useful papers involving calibration, validation, and application of FAST.Farm to wake steering can be found here: [https://onlinelibrary.wiley.com/doi/full/10.1002/we.2756](https://onlinelibrary.wiley.com/doi/full/10.1002/we.2756) and [WESD - Load assessment of a wind farm considering negative and positive yaw misalignment for wake steering](https://wes.copernicus.org/preprints/wes-2024-6/). Best regards, ---
**Author:** ![Ipsita.Mishra](https://avatars.discourse-cdn.com/v4/letter/i/5daacb/32.png) [@Ipsita.Mishra](https://forums.nlr.gov/u/Ipsita.Mishra)\ **Post date:** [October 18, 2024, 3:41pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/3 "2024-10-18T15:41:07Z")
Thank You Dr. Jason for supporting me with relevant papers. I have gone through the first paper which you have mentioned in Sl.No.1. I am going through other papers too. I have certain observations and queries which I will post after I completely understanding the process adopted in each paper and how can I use it for my research. Regards Ipsita Mishra ---
**Author:** ![Ipsita.Mishra](https://avatars.discourse-cdn.com/v4/letter/i/5daacb/32.png) [@Ipsita.Mishra](https://forums.nlr.gov/u/Ipsita.Mishra)\ **Post date:** [November 14, 2024, 5:56pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/4 "2024-11-14T17:56:48Z")
Hello Dr. Jason, I went through your first paper ([https://onlinelibrary.wiley.com/doi/full/10.1002/we.2785](https://onlinelibrary.wiley.com/doi/full/10.1002/we.2785)), which includes one of the result analyses of Dr. Fleming’s paper ([https://onlinelibrary.wiley.com/doi/epdf/10.1002/we.1810](https://onlinelibrary.wiley.com/doi/epdf/10.1002/we.1810)), which I was interested in running in FAST.Farm. The results are quite interesting to know that power outputs with yaw settings using FAST.Farm tool is different from the LES simulation with the SOWFA tool, although there is a good trend matching. I want to use the polar and curled wake model to generate the same case. My question is: 1. Is only 1 inflow wind file @8m/s generated using TurbSim for only 1 seed or multiple seeds? 2. A series of FAST. Farm simulations were run for all different yaw settings. So can I get the details of the yaw settings that I have to change in the servodyn input file? 3. Is it ok to share the FAST.Farm input file, if it is available open-source? This will help in moving forward as extension to this work which is my research objective. ---
**Author:** ![Jason.Jonkman](https://dub1.discourse-cdn.com/nrel/user_avatar/forums.nlr.gov/jason.jonkman/32/3086_2.png) [@Jason.Jonkman](https://forums.nlr.gov/u/Jason.Jonkman)\ **Post date:** [November 14, 2024, 9:21pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/5 "2024-11-14T21:21:24Z")
Dear @Ipsita.Mishra, Here are my responses: 1. The FAST.Farm analysis published in that paper used 1 seed of 1-hour TurbSim inflow. 2. In this case, the wind turbines were modeled rigidly, with only the generator DOF enabled. So, ServoDyn controlled the torque, but not the yaw. Rather, separate simulations where run each with fixed yaw error of the first turbine, by changing `NawYaw` in ElastoDyn between simulations. 3. I was not the one who ran these simulations and don’t have access to the input files. Perhaps Emmanuel Branlard (the lead author) can respond. Best regards, ---
**Author:** ![Ipsita.Mishra](https://avatars.discourse-cdn.com/v4/letter/i/5daacb/32.png) [@Ipsita.Mishra](https://forums.nlr.gov/u/Ipsita.Mishra)\ **Post date:** [November 14, 2024, 9:30pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/6 "2024-11-14T21:30:41Z")
Hi Dr. Jason, Thank you for your prompt response and giving a clear answer. For Q2. I meant the ‘Nacelle-Yaw control’ settings in the ServoDyn input file. Like at what time the turbine 1 starts yawing and till how many secs out of 1hour. I am attaching the image of the ‘Nacelle-Yaw control’ with highlighted points about which I was asking. ![image](https://europe1.discourse-cdn.com/nrel/original/2X/8/8b035ea3b2799c7eff235eb9595f08107050e8d3.png) ---
**Author:** ![Jason.Jonkman](https://dub1.discourse-cdn.com/nrel/user_avatar/forums.nlr.gov/jason.jonkman/32/3086_2.png) [@Jason.Jonkman](https://forums.nlr.gov/u/Jason.Jonkman)\ **Post date:** [November 14, 2024, 9:38pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/7 "2024-11-14T21:38:56Z")
Dear @Ipsita.Mishra, These simulations did not involve active yaw control through ServoDyn, which is unused when `YawDOF` = FALSE in ElastoDyn, as was the case here. Rather fixed yaw was used based on `NacYaw`. Best regards, ---
**Author:** ![Ipsita.Mishra](https://avatars.discourse-cdn.com/v4/letter/i/5daacb/32.png) [@Ipsita.Mishra](https://forums.nlr.gov/u/Ipsita.Mishra)\ **Post date:** [November 14, 2024, 9:42pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/8 "2024-11-14T21:42:50Z")
Thank you so much. I will try running the case and share the results if I have any further issues. ---
**Author:** ![Emmanuel.Branlard](https://avatars.discourse-cdn.com/v4/letter/e/e495f1/32.png) [@Emmanuel.Branlard](https://forums.nlr.gov/u/Emmanuel.Branlard)\ **Post date:** [November 15, 2024, 11:29pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/9 "2024-11-15T23:29:37Z")
Hi, I’ve pushed the input files in the following git repository: > **[GitHub - ebranlard/ff-curl](https://github.com/ebranlard/ff-curl/tree/main)** > > main You’ll likely have to adapt them to the version of OpenFAST you are using, Emmanuel ---
**Author:** ![Ipsita.Mishra](https://avatars.discourse-cdn.com/v4/letter/i/5daacb/32.png) [@Ipsita.Mishra](https://forums.nlr.gov/u/Ipsita.Mishra)\ **Post date:** [November 16, 2024, 3:50pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/10 "2024-11-16T15:50:17Z")
Thank you so much. I have a quick question: Which version of OpenFAST are these files compatible with? ---
**Author:** ![Ipsita.Mishra](https://avatars.discourse-cdn.com/v4/letter/i/5daacb/32.png) [@Ipsita.Mishra](https://forums.nlr.gov/u/Ipsita.Mishra)\ **Post date:** [November 20, 2024, 10:35pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/11 "2024-11-20T22:35:13Z")
Hello Emmanuel, kind attn: Dr. Jason I tried running the case file shared with me. I also changed the OpenFAST input files as compatible to version 3.5.3. But the following error is reflected when I run the .fstf files. Maybe it is the version issue. Can you send me the FAST.FARM and OpenFAST exe file like so that it goes along with the case generated in your simulation. The error is shown below: FAST.Farm-v3.5.3 Compile Info: - Compiler: Intel(R) Fortran Compiler 2021 - Architecture: 64 bit - Precision: single - OpenMP: No - Date: Apr 11 2024 - Time: 20:51:36 Execution Info: - Date: 11/20/2024 - Time: 15:40:48-0600 Heading of the FAST.Farm input file: Sample FAST.Farm - input file Running AWAE. Running InflowWind. Reading a 101x35 grid (1000 m wide, 5 m to 345 m above ground) with a characteristic wind speed of 9.243 m/s. This full-field file was generated by TurbSim on 20-Nov-2024 at 10:33:02. forrtl: severe (170): Program Exception - stack overflowperiod of 3702.6 seconds). Image PC Routine Line Source FAST.Farm\_x64.exe 00007FF751651507 Unknown Unknown Unknown FAST.Farm\_x64.exe 00007FF74E79C01F Unknown Unknown Unknown FAST.Farm\_x64.exe 00007FF74E78F48F Unknown Unknown Unknown FAST.Farm\_x64.exe 00007FF74E5A13F4 Unknown Unknown Unknown FAST.Farm\_x64.exe 00007FF75112882E Unknown Unknown Unknown FAST.Farm\_x64.exe 00007FF751651710 Unknown Unknown Unknown KERNEL32.DLL 00007FFF62127374 Unknown Unknown Unknown ntdll.dll 00007FFF6251CC91 Unknown Unknown Unknown ---
**Author:** ![Jason.Jonkman](https://dub1.discourse-cdn.com/nrel/user_avatar/forums.nlr.gov/jason.jonkman/32/3086_2.png) [@Jason.Jonkman](https://forums.nlr.gov/u/Jason.Jonkman)\ **Post date:** [November 20, 2024, 10:57pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/12 "2024-11-20T22:57:42Z")
Dear @Ipsita.Mishra, Perhaps try upgrading to FAST.Farm within OpenFAST v3.5.4, where the known stack overflow issue ([FAST.Farm · Issue #2053 · OpenFAST/openfast · GitHub](https://github.com/OpenFAST/openfast/issues/2053)) has been fixed ([Fix for some stack overflow issues with FAST.Farm by andrew-platt · Pull Request #2452 · OpenFAST/openfast · GitHub](https://github.com/OpenFAST/openfast/pull/2452))? Best regards, ---
**Author:** ![Ipsita.Mishra](https://avatars.discourse-cdn.com/v4/letter/i/5daacb/32.png) [@Ipsita.Mishra](https://forums.nlr.gov/u/Ipsita.Mishra)\ **Post date:** [November 21, 2024, 6:05pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/13 "2024-11-21T18:05:45Z")
Thank You, Dr. Jason. The problem is fixed by upgrading to v3.5.4. However, a new error is reflected: T2:FARM\_InitialCO:FWrap\_t0:FAST\_Solution0:CalcOutputs\_And\_SolveForInputs:SolveOption2:SolveOption2 c\_Inp2AD\_SrvD:InflowWind\_CalcOutput:InflowWind\_GetSpatialAverage:CalculateOutput:IfW\_FlowField\_Get VelAcc:Grid4DField\_GetVel: Outside the grid bounds. I checked the same issues mentioned before in this forum and tried to check the fast.farm input files as per the suggestions given. NZ\_high is 17 and the dZ\_High is 10. Thus, the height of the high-resolution domain is 170 which is higher than the total turbine height in Z-direction (Zdist\_High) as 158.3 m (RefHt + high\_ext\*Drotor/2 - zbot). I have considered zbot = 1m and high\_ext = 1.1. Then where is it outside the grid bound? Please let me know if my understanding is correct and how can I correct this error. I have attached the image of my .fstf and inflow wind.inp files for reference. ![image](https://europe1.discourse-cdn.com/nrel/original/2X/4/4dc06027134a30f7bd1d2740a86b4fa9dbc2b399.png) inflow wind file ![image](https://europe1.discourse-cdn.com/nrel/original/2X/c/cf732d5f67921e0b23e48bf6ceb4d24cc7b3daba.png) ---
**Author:** ![Andy.Platt](https://avatars.discourse-cdn.com/v4/letter/a/df788c/32.png) [@Andy.Platt](https://forums.nlr.gov/u/Andy.Platt)\ **Post date:** [November 21, 2024, 10:31pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/14 "2024-11-21T22:31:35Z")
Hi @Ipsita.Mishra, I suspect the issue is with the `InflowWind_GetSpatialAverage` routine. This routine calculates the average wind speed across the rotor by sampling a set of predetermined points based on the rotor diameter. If this routine is getting the wrong value for the rotor diameter, then an out of bounds issue could occur. I will attempt to reproduce your error and find the what the issue is. Regards, Andy ---
**Author:** ![Ipsita.Mishra](https://avatars.discourse-cdn.com/v4/letter/i/5daacb/32.png) [@Ipsita.Mishra](https://forums.nlr.gov/u/Ipsita.Mishra)\ **Post date:** [November 21, 2024, 10:53pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/15 "2024-11-21T22:53:55Z")
Thank you so much for your support. ---
**Author:** ![Andy.Platt](https://avatars.discourse-cdn.com/v4/letter/a/df788c/32.png) [@Andy.Platt](https://forums.nlr.gov/u/Andy.Platt)\ **Post date:** [November 23, 2024, 11:33pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/16 "2024-11-23T23:33:11Z")
Dear @Ipsita.Mishra, After some digging, I found the issue. There is an error in how the rotor points are calculated for the disk average average plane resulting in an incorrect rotor projection. The effect of this is that this calculation currently requires points a half rotor diameter downstream of the rotor. This causes a bounds error in the `X` dimension the high resolution box around Turbine 2. For Turbine 1, your high resolution box extends from `X0_High=-77.7` to `95.2` (`X0_High + (NX_High-1) * dX_High`). This spans more than a half rotor diameter downstream of the turbine hub. for Turbine 2, your high resolution box extends from `X0_High=709.3` to `882.2` (`X0_High + (NX_High-1) * dX_High`). However, with the turbine sitting at 877 m, there is only 5 m of high resolution wind box behind it. WIth the error in the calculations for the rotor average wind speed, the incorrectly projected rotor is partially behind this box. I will submit a fix for this issue shortly. This will be included in our soon to be released v3.5.5 next week. In the meantime, you can either shift `X0_High` back by 40 m to 749.3 m, or increase `NX_High` to 22. Regards, ---
**Author:** ![Ipsita.Mishra](https://avatars.discourse-cdn.com/v4/letter/i/5daacb/32.png) [@Ipsita.Mishra](https://forums.nlr.gov/u/Ipsita.Mishra)\ **Post date:** [April 11, 2025, 9:02pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/17 "2025-04-11T21:02:45Z")
Hi Emmanuel, As I mentioned in the above messages, I am trying to re-generate the test case referred to in your paper [https://onlinelibrary.wiley.com/doi/10.1002/we.2785](https://onlinelibrary.wiley.com/doi/10.1002/we.2785) using FAST. Farm. You shared the files in the Github repository ([GitHub - ebranlard/ff-curl](https://github.com/ebranlard/ff-curl/tree/main)), and I ran the simulations for \*\* the polar wake model\*\* only and generated all .out files for T1 and T2 cases, ranging from yaw angle [-40:5:40]. Then, while plotting the power vs yaw angle for T1 and T, the T1 results matched with your generated results, but the T2 power results look to be high compared to the paper. I have attached my generated results image here: 1. Regenerated power plots ![image](https://europe1.discourse-cdn.com/nrel/original/2X/f/fa73de8210d8781c96db1e7a089e1051f7b6496d.png) 1. Power plots referred to in the paper ![image](https://europe1.discourse-cdn.com/nrel/original/2X/3/34799983e2d7ab1b0ddd70a5382b7b6c9202a600.png) I did the following checks in the input files: a) .fstf files checked for the wake mod set to ‘1’ for polar wake model, b) Eastodyn files for T1 and T2 are checked. One difference found is the rotor speed for T1 is 8 rpm and T2 is 9 rpm. This may cause the difference which I am thinking. c) Servodyn files of both the turbines remain the same except for the .dll files. Please let me why is this difference and what else I need to check and re-run to match the power plots. This will be very helpful. Regards Ipsita Mishra ---
**Author:** ![Ipsita.Mishra](https://avatars.discourse-cdn.com/v4/letter/i/5daacb/32.png) [@Ipsita.Mishra](https://forums.nlr.gov/u/Ipsita.Mishra)\ **Post date:** [April 14, 2025, 4:25pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/18 "2025-04-14T16:25:20Z")
In the published paper, the simulations were run for variable rotor speed. So I think you also run the files at T1 = 8 rpm and T2 =9 rpm. So, this is ruled out. I also find that the wind inflow files generated through TurbSim have a hub height of 175 m instead of 90 m (NREL 5MW). Will that make a difference? Please let me know where I am going wrong so I can rectify the simulation results before proceeding. ---
**Author:** ![Ipsita.Mishra](https://avatars.discourse-cdn.com/v4/letter/i/5daacb/32.png) [@Ipsita.Mishra](https://forums.nlr.gov/u/Ipsita.Mishra)\ **Post date:** [April 17, 2025, 3:21pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/19 "2025-04-17T15:21:54Z")
Hello Dr. Jason, can you please comment on my above questions, which I have posted for Mr. Emmanuel on the polar wake models power plots difference when compared to your paper? All details are given. If you need anything, I am available to answer that. I am eagerly waiting to hear the answer. Thank you for your guidance as always. Regards Ipsita Mishra ---
**Author:** ![Jason.Jonkman](https://dub1.discourse-cdn.com/nrel/user_avatar/forums.nlr.gov/jason.jonkman/32/3086_2.png) [@Jason.Jonkman](https://forums.nlr.gov/u/Jason.Jonkman)\ **Post date:** [April 17, 2025, 3:44pm UTC](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684/20 "2025-04-17T15:44:35Z")
Dear @Ipsita.Mishra – This is a question that would be better answered by @Emmanuel.Branlard; hopefully he can respond. [Next page](https://forums.nlr.gov/t/comparison-of-fast-farm-and-sowfa/7684.md?page=2)