SWMM5 table.c Summary

 The table.c file in SWMM 5 handles the manipulation and management of Curve and Time Series objects, which are essential for defining relationships between variables (e.g., rainfall rates, runoff, pollutant loads). It provides functions for reading, writing, and processing data for curves (used to define relationships between variables) and time series (used for time-based data such as rainfall, temperature, etc.). This file is key for processing input data, interpolating values, and performing lookups in the context of the SWMM simulation.

Key Functions in table.c:

1. table_interpolate:

   • This function performs linear interpolation between two data points (x1, y1) and (x2, y2) to estimate the value (y) corresponding to an x value that lies between x1 and x2.

2. table_readCurve:

   • Reads a curve table from input data. This function handles the definition of curves used for mapping variables to one another, such as flow vs. depth or other relationships.

3. table_readTimeseries:

   • Reads time series data from input and stores it in a TTable object. This is used for time-varying data like rainfall, temperature, and other time-dependent parameters.

4. table_addEntry:

   • Adds an entry (x, y) to a table. This is used to store data points in both curves and time series tables.

5. table_deleteEntries:

   • Deletes all entries in a table. This is useful for cleaning up memory when a table is no longer needed.

6. table_init:

   • Initializes the properties of a TTable structure, setting default values for curve and time series tables.

7. table_validate:

   • Ensures that the data in a table is valid, checking that the x-values are in ascending order. If not, it returns an error.

8. table_getFirstEntry & table_getNextEntry:

   • These functions allow you to retrieve the first and subsequent entries (x, y) from a table. They are used for processing tables and performing lookups.

9. table_lookup:

   • Looks up the y-value corresponding to an x-value in a curve or time series table. It returns the interpolated value if necessary.

10. table_getMaxY:

    • Retrieves the maximum y-value from the initial part of the table, useful for determining the extent of a table.

11. table_getStorageVolume & table_getStorageDepth:

    • These functions are used in SWMM for tables that define storage curves, particularly for stormwater detention or retention basins.

12. table_tseriesInit:

    • Initializes a time series table, setting the first and last date/time entries, and preparing it for interpolation and lookups.

13. table_tseriesLookup:

    • Looks up a y-value corresponding to a given x (date/time) value in a time series table. Supports interpolation and extrapolation.

14. table_getNextFileEntry:

    • Retrieves the next data entry (x, y) from an external file, which is essential for reading time series or curve data from files.

15. table_parseFileLine:

    • Parses a line from a time series or curve file, extracting the x (date/time) and y (value) pairs for storage in the table.

Table Structure and Use in SWMM:

• Curve Tables: These are used to define relationships between two variables, like flow vs. depth or other physical properties.
• Time Series Tables: These store time-varying data, such as rainfall, temperature, and other temporal input data for simulations.

Functions for Interpolation and Lookup:

• Interpolation: Functions like table_interpolate and table_lookup are used to estimate values between known data points in the table, allowing the model to handle time-varying inputs like rainfall.
• Extrapolation: Functions like table_tseriesLookup handle extrapolation when time series data is outside the existing table range.

Use of External Files:

• Some tables are loaded from external files (e.g., time series data for rainfall). The functions handle file reading and parsing, as seen in table_getNextFileEntry and table_parseFileLine.

Validation:

• The table_validate function ensures the integrity of table data, ensuring that x-values in the table are ordered correctly, which is important for interpolation and lookups.

Summary:

The table.c file in SWMM 5 is crucial for managing and processing curve and time series data. It enables interpolation, extrapolation, and lookup of values from these data structures, which are used throughout the SWMM simulation for various physical processes like runoff, routing, and water quality. The file also handles input parsing, validation, and memory management for tables, making it a core component of the SWMM computational engine.