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Collocation Baseline (bvp4c / bvp5c)

Mathematical Modelling — Fluid Dynamics & Heat TransferNumerical analysis; boundary-layer similarity theory

Symbol

Lobatto IIIa

MATLAB’s finite-difference collocation solvers used as the independent baseline: a C¹ piecewise-cubic solution forced to satisfy the ODE at Lobatto points on an adaptive mesh, with the boundary conditions imposed GLOBALLY (no shooting). Agreement between this and the shooting/RK4 route is itself a validation.

Dimension I

Definition

What it is — and what it is not

What it is
  • S1bvp4c is a COLLOCATION method: a C¹ piecewise cubic satisfying the ODE at three Lobatto IIIa points per mesh interval, with the boundary conditions imposed globally and the mesh adapted to control the residual. [1.1]
Common misconceptions
  • S2“bvp4c is a fourth-order Runge–Kutta/shooting solver” — it is not: it never integrates an IVP and never guesses initial slopes. The “4” refers to the fourth-order accuracy of the collocation solution. Shooting + RK4 is a SEPARATE strategy, used here as an independent cross-check. [1.1]

Dimension II

In practice

How to deal with it

How to deal with it
  • S3Use bvp4c/bvp5c first (robust to poor guesses), then refine/cross-check with shooting + RK4; agreement across the two method families is itself evidence of correctness. [1.1]

References

  1. Shampine & Kierzenka (2001); Shampine, Kierzenka & Reichelt (2003).

    • 1.1

      bvp4c reference — A three-stage Lobatto IIIa COLLOCATION method: C¹ piecewise-cubic solution with residual control on an adaptive mesh — not a shooting method.

      Established
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