The Calibration Options dialog box controls optimization properties and simulation options during a model calibration simulation. Within this dialog box, you can specify the convergence parameters, advanced GA options, and the objective function type. The following items appear for the Calibration Options dialog box.
Force Calibration on Pipe Groups (Calibrate All the Pipes In Groups) - Check this option to force all the pipes within a pipe group to be calibrated together even though some of them may have their own wall reaction coefficients defined.
Global (Default) Pipe Wall Reaction Coefficient - This reflects the global rate at which a chemical will grow or decay due to reactions with the pipe walls over time. It is set according to the setting in the Simulation Options. This global rate is applied to any pipe which is not defined in a pipe calibration group and does not have its own wall reaction coefficient specified.
Concentration Measurement Evaluation Threshold - Define an error threshold to evaluate the concentration measurements. Differences below the threshold will be shown in green in the "% Difference" column while differences above the threshold will be shown in red.
The optimization module will terminate its iterative solution refinement process when one of the following four criteria is satisfied.
Fitness Threshold - Prescribe a convergence criterion for the optimization routine used to minimize the selected fitness function. The iterations end when the fitness threshold is reached. WQ Calibrator will not allow a value smaller than 0.1 percent (0.001) to be used.
Least Fitness Improvement (%) - Prescribe another convergence criterion for the optimization routine used to minimize the selected fitness function. The optimization ends if it fails to improve the total fitness better than the Least Fitness Improvement ratio (%) over the Least Improvement Generation.
Least Improvement Generation - Specify the maximum number of consecutive generations with improvements of the fitness function not greater than the Least Fitness Improvement ratio. WQ Calibrator will not allow a value greater than 500 (or less than 2) to be used.
Maximum Trials - The maximum number of solution iterations that WQ Calibrator should employ when determining improved sets of pipe wall coefficients. The maximum number of trials allowed is 500,000. This criterion is checked after each computed generation.
In case a calibration run is not successful in reaching a converged solution, it is expected that the assumed network topology (i.e., a valve may be closed, an important pipe may be missing) may be in error, the observed field measurements or boundary conditions are in error, and/or the original calibration groupings need to be examined and/or adjusted.
Advanced GA Options... - Launches the Advanced GA Options dialog box where you are able to specify advanced GA parameters to improve convergence and accuracy.
Convergence Method Fitness Measurement - Define the objection (fitness) function type. Three options for the objective function are available. These are:
where N represents the total number of junction nodes with concentration measurements, Mi represents the total number of measurements associated at junction node i, Csimij represents the jth simulated data at junction node i and Cobsij is the jth measured data at junction node i. The default objective function is type 1.
The Type 1 fitness function is recommended. Type 3 is the most stringent.