Finding Similarity Solutions for Boundary Value Problems

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SUMMARY

The discussion focuses on applying the similarity solution method to the boundary value problem defined by the equation u_t = k u_{xx}, with specific boundary conditions. The user seeks guidance on deriving the similarity variable η = x/√(kt) and the function u = √(kt) f(η). The procedure involves substituting the similarity variable into the equation and solving for the unknown function f(η) to satisfy the given boundary conditions. The discussion emphasizes the importance of understanding the transformation to similarity variables in solving such problems.

PREREQUISITES
  • Understanding of boundary value problems in partial differential equations.
  • Familiarity with the similarity solution method in mathematical analysis.
  • Knowledge of the heat equation and its properties.
  • Basic skills in solving ordinary differential equations derived from partial differential equations.
NEXT STEPS
  • Study the derivation of similarity variables in boundary value problems.
  • Learn about the method of separation of variables for solving PDEs.
  • Explore the application of the heat equation in various physical contexts.
  • Investigate numerical methods for approximating solutions to boundary value problems.
USEFUL FOR

Mathematicians, physicists, and engineers working on boundary value problems, particularly those interested in the application of similarity solutions in partial differential equations.

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This question is also posted at http://www.mathhelpforum.com/math-help/f59/similarity-solutions-185537.html. Please view that post instead for better formatting.

The original question is:
Try and apply the Similarity solution method to the following boundary value problems for u(x,t).

u_t = k u_{xx} for all x > 0 with boundary conditions
u_x(0,t) = 1
u(x,t) \to 0 as x \to \infty
u(x,0) = 0 for x > 0.

I know from my tutorial that I should first find u = \sqrt{kt} f(\eta) where f is an unknown function of similarity variable \displaystyle \eta = \frac{x}{\sqrt{kt}}. What I don't know is how to find the similarity variable \eta and the formula u = \sqrt{kt} f(\eta).

Please tell me the procedure for finding similarity solution. Thank you in advance.
 
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