SWMM - Control Rules - Arithmetic Expressions

In addition to a simple condition placed in a single variable, a control condition clause can also contain an arithmetic expression consisting of several variables whose value is compared. Thus, the format of a condition clause can be extended as follows:

 EXPRESSION  relation   value   

Or:

 EXPRESSION  relation   variable

Where the expression is defined on a separate line before its first use in a rule using the format:

EXPRESSION  name = f(variable1, variable2, ...)

The f(...) function can be any well-formed mathematical expression containing one or more named variables, as well as any of the following (case-insensitive) mathematical functions and operators:

• abs(x): absolute value of x
• sgn(x): +1 for x >= 0 or -1 otherwise
• step(x): 0 for x <= 0 and 1 otherwise
• sqrt(x): square root of x
• log(x): logarithm base e of x
• log10(x): base 10 logarithm of x
• exp(x): e raised to the power of x
• sin, cos, tan, cot: standard trigonometric functions
• asin, acos, atan, acot: inverse trigonometric functions
• sinh, cosh, tanh, coth: hyperbolic trigonometric functions
• +, -, *, /, ^: standard operators and any level of nested parentheses

Here is an example of using this feature:

VARIABLE  P1_flow = LINK 1 FLOW
VARIABLE  P2_flow = LINK 2 FLOW
VARIABLE  O3_flow = Link 3 FLOW

EXPRESSION Net_Inflow = (P1_flow + P2_flow)/2 - O3_flow
EXPRESSION Test =  asin( sin(P1_flow) +  sin(P2_flow)))/2 - O3_flow

RULE 1
IF   Net_Inflow > 0.1
THEN ORIFICE 3 SETTING = 1
ELSE ORIFICE 3 SETTING = 0.5

On SOLIDOS (command SWMMCONTROLS) , the expressions are created in the table below:

Veja também: Regras Controles do SWMM