Chapter 32: Problem 4
Investigate the convergence of the following iteration scheme for the friction law (32.52) $$\Lambda_{n}=A \log \operatorname{Re}_{\delta}+B+C-A \log \Lambda_{n-1}, \quad \Lambda_{0}=1,$$ where \(\Lambda_{n}\) is the \(n\) th approximant to \(\Lambda=U_{\delta} / u_{0} .\) Find the approximant sequence for \(A=2.44, B=5\), \(C=0\) and \(\operatorname{Re}_{\delta}=10^{5}\).
Short Answer
Step by step solution
Initialize Constants for Iteration
Setup Iteration Function
First Calculation (n=1)
Second Calculation (n=2)
Continue Calculations for Convergence
Check for Convergence
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Iteration Scheme
- Start with an initial guess: This is usually denoted as \( \Lambda_0 \), and in the problem, it begins with 1.
- Use a function: The function incorporates parameters like \( A, B, C, \) and values such as \( \operatorname{Re}_{\delta} \).
- Calculate subsequent approximations: Compute \( \Lambda_1, \Lambda_2, \ldots \) until a steady result or convergence is observed.
Logarithmic Functions
- Logarithms help simplify exponential expressions: They are crucial in reducing multiplication into addition.
- Facilitates iterative calculations: By making the computation straightforward and manageable in each step, especially in finding successive approximations.
- Useful in convergence criteria: Logarithms help determine if a sequence converges by simplifying differences between terms.
Convergence Analysis
- Observe changes between successive iterations: When the difference between \( \Lambda_n \) and \( \Lambda_{n-1} \) becomes negligible, convergence is likely.
- Consider initial values and function behavior: Ensure that \( \Lambda_0 \) isn't too far from the expected solution and the function behaves smoothly near the target value.
- Use convergence criteria: Common tests involve examining the limit of \( \Lambda_n \) as \( n \) approaches infinity to ensure it stabilizes to a specific value.