MHB What Determines the Time Dependent Value of A[t] in Quasi-Static Approximations?

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In the discussion, a student seeks clarification on the time-dependent value of A[t] in quasi-static approximations for their thesis. The response suggests that A[t] is initially treated as a constant to simplify integration or solving differential equations. Once the solution is obtained, A[t] can be substituted back into the results for an approximate solution. The conversation emphasizes the importance of understanding the underlying concepts rather than just the mathematical procedures. This approach aids in grasping the significance of A[t] in the context of hot oil/watering jobs.
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Hello,

I'm working on my bachelor's thesis, and I ran into a problem. In the text they say: "For hot
oil/watering jobs, U is typically large enough that f(t) is closer to a constant temperature than
constant flux boundary condition. In the quasi-static approximation,
these integrals are solved assuming that A[t] is a constant independent of time and then the
appropriate time dependent value of A[t] is plugged into the approximate solutions."

I don't understand how to do it. What will be that "appropriate time dependent value of A[t]"?View attachment 7574

I will be grateful for any advice,
Full text in the attachment,

Thanks in advance. Full text View attachment 7575
 

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mk747pe said:
Hello,

I'm working on my bachelor's thesis, and I ran into a problem. In the text they say: "For hot
oil/watering jobs, U is typically large enough that f(t) is closer to a constant temperature than
constant flux boundary condition. In the quasi-static approximation,
these integrals are solved assuming that A[t] is a constant independent of time and then the
appropriate time dependent value of A[t] is plugged into the approximate solutions."

I don't understand how to do it. What will be that "appropriate time dependent value of A[t]"?

I will be grateful for any advice,
Full text in the attachment,

Thanks in advance. Full text

Hi mk747pe! Welcome to MHB! ;)

Your documents seem to be missing some context.
Anyway, my current interpretation is that we presumably have a fully known function A[t].
And we want to integrate something or solve some differential equation (that I can't seem to find) that includes A[t].
To do so, we assume A[t] to be constant to make it easier to integrate or solve the equation.
That is, we replace A[t] everywhere by A.
And when we have found the solution, we replace every occurrence of A again by A[t] for an approximate solution.

Btw, since this seems to be more about understanding what it all means than about actually integrating or solving a differential equation, I'm moving your thread to Other Advanced Topics.
 
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