Initial upload of tutorial 2

docs/tutorials/2-creating-subordinate-excels.md

+# Tutorial 2: Creating subordinate Excel files
+
+The Wind Energy Toolbox has a workflow for automatically running design load 
+bases (DLBs) on Gorm.
+This workflow has the following steps:
+1. [Create a master Excel sheet defining each case in the DLB](https://gitlab.windenergy.dtu.dk/toolbox/WindEnergyToolbox/blob/master/docs/tutorials/1-creating-master-excel.md)
+2. Create subordinate Excel sheets from each tab in the master Excel sheet
+3. Create htc files and PBS job scripts for each requisite simulation using 
+the subordinate Excel files and a master htc file.
+4. Submit all PBS job scripts to the cluster
+5. Post-process results
+6. Visualize results
+
+This tutorial presents how to accomplish Step 2.
+
+Note that it is possible to customize your simulations by skipping/modifying 
+steps.
+Such a procedure will be discussed in a later tutorial.
+
+If there are any problems with this tutorial, please [submit an issue](
+https://gitlab.windenergy.dtu.dk/toolbox/WindEnergyToolbox/issues).
+
+## 1. Background: Subordinate Excel Files
+
+The subordinate Excel files are a series of basic Excel files that are 
+generated from the master Excel file. (See our tutorial on generating the 
+master Excel file [here]( https://gitlab.windenergy.dtu.dk/toolbox/WindEnergyToolbox/blob/master/docs/tut orials/1-creating-master-excel.md).)
+There is a different subordinate Excel file for every tab in the master Excel 
+file, except for the "Main" tab, one for each case to simulate (e.g., design 
+load case 1.2 from IEC-61400-1).
+Each subordinate Excel file has a single tab that lists the different tag 
+values for the htc master file in the column, and each row corresponds to a 
+different htc file to be generated.
+The generation of the htc files from the subordinate Excel files is discused 
+in the next tutorial.
+
+
+## 2. Tutorial
+
+The generation of the subordinate Excel files is done using the 
+[GenerateDLS.py](https://gitlab.windenergy.dtu.dk/toolbox/WindEnergyToolbox/blob/master/wetb/prepost/GenerateDLCs.py)
+function in the Wind Energy Toolbox.
+On Gorm, the command can be executed from the htc directory with the master 
+Excel file as follows:
+```
+export PATH=/home/python/miniconda3/bin:$PATH
+source activate wetb_py3
+python /home/MET/repositories/toolbox/WindEnergyToolbox/wetb/prepost/GenerateDLCs.py [--folder=$FOLDER_NAME] [--master=$MASTER_NAME]
+source deactivate
+```
+
+The ```source activate wetb_py3``` and ```source deactivate``` are 
+Gorm-specific commands to activate the Wind Energy Toolbox Python environment.
+Note that ```--folder``` and ```--master``` are optional flags to specify the 
+name of the folder to which the subordinate Excel files should be written to 
+and the name of the master Excel file, respectively.
+The default values for these two options are './' (i.e., the current 
+directory) and 'DLCs.xlsx', respectively.
+This command should successfully have created a folder with all of the 
+required subordinate Excel files.
+
+
+## 3. Issues
+
+If there are any problems with this tutorial, please [submit an issue](
+https://gitlab.windenergy.dtu.dk/toolbox/WindEnergyToolbox/issues).
+We will try to fix it as soon as possible.
+