added Flows section

3.0_technical_documentation.md

@@ -594,6 +594,36 @@ Each story has its own unique feedback loop that shows named balancing and reinf
 
 14. **Exit:** Click to close this window.
 
+##### Flows
+
+Flow meters are visualized in Sankey form. Sankey is a data visualization technique that uses a flow diagram to depict the movement of a quantity (Veterans) through stocks (a state of care) over time. The width of the arrows is proportioinal to the flow quantity, which allows viewers to easily identify the largest flows within a system.
+
+<img alt="Image of stock or state indicator key." src="https://raw.githubusercontent.com/lzim/mtl/gh-pages/images/stock_state_indicator_key.png" style="float: right; margin: 25px">
+
+The stock or state indicator key is located at the top right of each flow diagram pop-up for quick reference. A stock is a state of care in which patients can accumulate over time. In the Sim UI, stocks change coor based on their state. When the invlow exceeds the outflow, patients accumulate and the stock is red. When the inflow is equal to, or less than the outflow, patients flow and the stock is blue. This allows viewers to easily identify bottlenecks within a system.
+
+Each module has its own unique flow dynamics. For illustrative purposes, the Psychotherapy Flow Diagram is used as an example below to orient you to general flow diagram features.
+
+<img alt="Image of psychotherapy flow diagram." src="https://raw.githubusercontent.com/lzim/mtl/gh-pages/images/psy_flow_diagram.png">
+
+1. **Tutor:** The Tutor button will introduce you to the features of this page. 
+
+2. **Appointments:** The top part of the diagram depicts the flow of appointments within PSY.
+
+3. **Key:** Refer to this key to understand color coding of the stock or state indicator. 
+
+4. **Patients:** The bottom part of the diagram depicts the flow of patients within PSY.
+
+5. **Dial:** A dial indicates rate of flow into the stock at the point of the arrow—here, the dial indicates the number of patients per week starting their first visit.
+
+6. **Proportional Flow Lines:** The width of the flow lines under this pin are proportional to the flow quantity. To aid in comparing inflows and outflows, they appear in the same fixed order.
+
+7. **Stock Rectangle:** This stock indicates the total number of patients scheduled for their first visit. The level of a stock is determined by the rates of flow into and out of it.
+
+8. **”i” icons:** Click any “i” icon in the Sim UI for a pop-up with more information about the labeled feature.
+
+9. **Exit:** Click to close this window.
+
 ##### Decision Meters
 
 Decision Meters are a quick infographic-based way to identify the highest leverage points and are highly supportive of clinical decision-making; they are for "decider" users who need systems thinking insights. The meters provide a visual interface that provides real-time feedback on ranges in our primary _MTL_ units of patients/week and appointments/week. The traffic light reflects the current state results and _recommendation_ of future state results. Through dialogue with decision-makers, consultants and field users manually input values into this graphic generator so the decision meters reflect the recommendations based on the alternative scenarios/experiments run by the learner. Decision meter numbers should be reflected in the "D" box of the Q/H/F/D outputs text field within the Sim UI, usually as ranges of numbers.