Model Parameters

On the Model Parameters page the properties of the model parameters that are defined in the model parameter files are specified. The parameter table is automatically created by AUTOCAL based on the specifi­cations given in the template files on the Simulation Specifications page.

 

The following properties are specified in the table:

ID value

The ID value is the identification tag value given for the parameter in the tem­plate file.

Keyword/Line no

The keyword is an identification string that shows the location of the parame­ter in the PFS model input file. The first part of the string is the name of the template file. This is followed by the hierarchy of PFS sections separated by dots. The last part of the string is the PFS keyword. If the parameter file is not a MIKE Zero PFS file, the line No. where the parameter is located is shown.

For each parameter, the following has to be specified:

Name

The user must specify a unique name for each parameter. This name must not include white spaces. In addition, if the parameter is included as an inde­pendent parameter in an equation, arithmetic symbols and function names used by the equation parser must not be used as part of the parameter name.

Parameter type

The parameter may be defined as either a Variable parameter, a Constant parameter or a Dependent parameter. A variable parameter is a parameter that is changed by AutoCal according to the chosen simulation option. For a variable parameter the Initial value, Lower bound and Upper bound need to be defined. A constant parameter is set to the value defined in the Initial value field. A dependent parameter is defined as a function of the other parameters. In this case the Equation must be specified.

Initial value

The Initial value is the value used by AutoCal for performing a single scenario run. If the Local sensitivity analysis option is chosen, the sensitivity coeffi­cients are evaluated around the initial parameter set.

Lower bound

The Lower bound specifies the lower limit of the feasible parameter values in the parameter optimisation.

Upper bound

The Upper bound specifies the upper limit of the feasible parameter values in the parameter optimisation.

Transformation

The parameter may be used in AutoCal as its native value by setting the transformation field to Real or as its logarithmic transformed value by setting the transformation field to Logarithmic. A logarithmic transformation is gener­ally recommended if the feasible range of the parameter varies over orders of magnitude.

Equation

If a parameter is defined as a dependent parameter, an equation must be given to define the parameter as a function of the available variable parame­ters. AutoCal uses an equation parser that supports the general arithmetic operators (+,-,*,/) as well as a number of mathematical functions. The list of available mathematical functions is given in Table 1.1.

Table 1.1             Mathematical functions used by the equation parser (X and Y are varia­ble names)

Syntax

Function

SQR(X)

Square function

SQRT(X)

Square root function

SIN(X)

Sinus function. SIN returns the sine of the angle X in radians

COS(X)

Cosinus function. COS returns the cosine of the angle X in radians

TAN(X)

Tangent function. TAN returns the tangent of the angle X in radians

COTAN(X)

Cotangent function. COTAN returns the cotangent of the angle X in radians

ATAN(X)

ArcTangent function

EXP(X)

Exponential function

LN(X)

Natural logarithmic function

LOG(X)

10 based logarithmic function

SINH(X)

Sinus Hyperbolic function

COSH(X)

Cosinus Hyperbolic function

INTPOW(X,Y)

The INTPOW function raises X to an integer power Y, e.g. INTPOW(2, 3) = 8. Note that the result of INTPOW(2, 3.4) = 8 as well

POW(X,Y)

The POW function raises X to any power Y

ABS(X)

Absolute value

SIGN(X)

SIGN(X) returns -1 if X<0; +1 if X>0, 0 if X=0

TRUNC(X)

Discards the fractional part of a number, e.g. TRUNC(3.2) is 3

MIN(X,Y)

Minimum of X and Y, e.g. MIN(2,3) is 2

MAX(X,Y)

Maximum of X and Y, e.g. Max(2,3) is 3

As an example, suppose Y is to be expressed as a function of the variables X1, X2 and X3 as 5 times variable X1 minus the square of variable X2 plus 2 times the natural logarithm of X3, the Equation field for Y should be written:

5*X1-SQR(X2)+2*LN(X3)

Comment

Optionally a comment can be written for the parameter.

Model parameter update

If parameter values are updated or deleted in the model parameter files, the model parameter table is automatically updated.