My program does not stop at the desired time

[afesenbek]

I have a for loop that is s=o to tf step dt, but the program never stops at the tf value. I just have no idea what I am doing wrong or what I need to add into my program. I have the whole program shown below. The basic concept is one dimensional heat transfer. I have all the right equations and things, but I just need to know how to make it stop at the time I want it to for tf being time final. Thank you!

Private Sub CommandButton1_Click()
'Alexis Fesenbek
'1D Heat Transfer

'Dimension the variables
Dim dx, dt, a, TH, TL, tf, k, h As Double
Dim T(1, 10) As Double
Dim i, s As Integer

'Setting values to the variables
TH = 100
TL = 0
dx = 0.1
dt = 0.1
a = Worksheets("Sheet1").Cells(13, 3).Value
tf = Worksheets("Sheet1").Cells(12, 3).Value
h = Worksheets("Sheet1").Cells(15, 3).Value
k = Worksheets("Sheet1").Cells(16, 3).Value

'Setting all the temps to the TH

'T(0, 0) = TL
'T(0, 10) = TL
For i = 0 To 10
T(0, i) = TH
Next i



'The time loop and correction for the ends of the simulation
For s = 0 To tf Step dt

T(0, 0) = (T(0, 1) * k / dx - h * TL) / (h + k / dx)
T(0, 10) = (T(0, 9) * k / dx - h * TL) / (h + k / dx)

'for loop for the simulation equation
For i = 1 To 9
T(1, i) = T(0, i) + (a * dt) / (dx) * (T(0, i - 1) - 2 * T(0, i) + T(0, i + 1))
Next i

'setting new values to previous values
For i = 1 To 9
T(0, i) = T(1, i)
Next i

'writing the values to the worksheet
For i = 0 To 10
Worksheets("Sheet1").Cells(4, 3 + i).Value = T(0, i)
Next i

Next s

End Sub

[Ed_Collins]

Have you tried stepping through your code, one line at a time, in the DEBUG mode?

When you do this you can look at the current values of all of the variables, and determine why the FOR NEXT loop isn't stopping.

[Greg M]

Hi there,

Your problem involves the following statements:

Please Login or Register  to view this content.

The variable "s" is declared as an integer variable.

The For loop initialises the variable "s" with a value of zero, and then attempts to increment its value by 0.1 (dt) on each iteration of the loop.

Because it is declared as an integer variable, "s" can never increase its value by an amount of less than one, and consequently remains at zero regardless of how many times the For loop is executed.

Declare "s" as a variable of type Double and see if your code works correctly.


Note: your Dim statements are probably not doing what you intend! The statement:

Please Login or Register  to view this content.

declares the variable "i" as being of type VARIANT, and the variable "s" as being of type Integer. You should probably be using:

Please Login or Register  to view this content.

or:

Please Login or Register  to view this content.

Hope this helps - please let me know how you get on.

Regards,

Greg M