Index
Functional dependence of parameter
Ver: 1
 

DESCRIPTION

In the context of time-dependent tasks, material parameters or boundary condition parameters can be a function of time (e.g. changing flow rate).

In Polyflow version 3, any problem parameter can be defined as an algebraic function of time t .  This menu will appear just after the definition of each parameter,  and the function defined in this menu will multiply the value previously defined.   In order to avoid to generate an excessive number of forms,  this menu will only appear whenever the mode is "EVOL ON".  This can be defined by either hitting the EVOL button in the top menu bar,  or by entering the EVOL keyword in MENUS mode.   This mode is turned off again by hitting EVOL once more.

When the task setup is of the transient type, the "Time-dependence" menu appears after the definition of parameters which might be a function of time.

During the time-marching process, the value of a specific parameter will be calculated as the product of its nominal value and the function of time selected for that particular parameter.  Those parameters will appear in the listing as well.

Implemented functions are as follows :

  OPTIONS
 
 -1 
 Upper level menu
0
 F(S) = User Defined Function
Allows the user to enter the index his own function of time. This function will be evaluated at run-time by CLIPS interpreter. (cfr 'User Defined Functions' chapter of the User's Manual).
1
 Time-independent
This is the default setup
2
 f(t) = t
Linear function of time.
Frequently used for flow rates changing with time.
3
 f(t) = 1/t
Inverse function of time.
Not available if tinit = 0.0
4
 f(t) = a + b*t + c*t**2 + d*t**3 
Third order polynomial
5
 f(t) = ramp function
This is a function with 4 parameters (a,b,c,d) representing the corner values of a ramp function as follows:


 
6
 f(t) = a * cos( b*t + c ) + d + e*t
A cosine function
7
 f(t) = a * t**b + c * t**d
Rational exponents of t
8
 f(t) = a * exp( b*t ) + c + d*t
Exponential function (e-base)
9
 f(t) = double ramp function
This is a function with 7 parameters (a,b,c,d,e,f,g) representing the corner values of a double ramp function as follows:


 
10
 f(t) = trapezoidal wave
This is a function with 6 parameters (a,b,c,d,e,f) representing a 'trapezoidal wave' as follows:


 
11
 f(t) = H step function
This is a function with 4 parameters (a,b,c,d) increasing or decreasing step by step as follows:


 
12
 Modify the value of a
To enter the "a" parameter in laws (4 to 11)
13
 Modify the value of b
To enter the "b" parameter in laws (4 to 11)
14
 Modify the value of c
To enter the "c" parameter in laws (4 to 11)
15
 Modify the value of d
To enter the "d" parameter in laws (4 to 11)
 16 
 Modify the value of e
To enter the "e" parameter in laws (6, 9 and 10)
17
 Modify the value of f
To enter the "f" parameter in laws (9 to 10)
18
 Modify the value of g
To enter the "g" parameter in laws (9)
EXAMPLES For an transient problem starting at a low flow rate and ending at a flow rate of Q, enter :
Q as the flow rate; select function 2.
The calculation will start at a flow rate = Q * (tinit + Dtinit) SEE ALSO