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Find the first-order forward difference approximation of \((\frac{\partial u}{\partial x})_{i,j}\) using the Taylor series expansion.(a) \(\frac{u_{i,j+1}-u_{i,j}}{2 \Delta x}\)(b) \(\frac{u_{i+1,j}-u_{i,j}}{2 \Delta x}\)(c) \(\frac{u_{i,j+1}-u_{i,j}}{\Delta x}\)(d) \(\frac{u_{i+1,j}-u_{i,j}}{\Delta x}\)The question was posed to me in an online quiz.I want to ask this question from Finite Difference Method in portion Finite Difference Methods of Computational Fluid Dynamics

Answer»

The correct option is (d) \(\frac{u_{i+1,j}-u_{i,j}}{\Delta x}\)

The best I can explain: To GET the first-order FORWARD DIFFERENCE APPROXIMATION,

The Taylor series expansion of ui+1,j is

\(u_{i+1,j}=u_{i,j}+(\frac{\partial u}{\partial x})_{i,j}\Delta x+(\frac{\partial ^2 u}{\partial x^2})_{i,j}\frac{(\Delta x)^2}{2}+⋯\)

\((\frac{\partial u}{\partial x})_{i,j}=\frac{u_{i+1,j}-u_{i,j}}{\Delta x}\).



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