CS 455/CSE 411/MATH 455: Review Questions, Spring 2008

This is a list of review questions for each section of the books and notes. The (*) symbol means some method or equation that would be given explicitly on the exam. This list of questions is not an inclusive list of exam questions, but is only intended to help with preparing for the exam.

[1] General Introduction to PDEs

  • Is (*) PDE linear? quasilinear? nonlinear?
  • Is (*) PDE elliptic? parabolic? hyperbolic?
  • When is a PDE well posed?
  • What are the characteristics of this PDE?
  • Are the boundary conditions specified correctly?
  • How do the characteristics help determine if a PDE is well posed?
  • What is the domain of dependence?
  • What is the range of influence?
  • Is (*) an advection equation?
  • Is (*) the Laplace equation? a heat equation? a wave equation?

[2] M&M Parabolic in 1D

  • Derive the analytical solution for the 1D Heat equation
  • Write down the forward/backward/centered difference approximation
  • Derive the local accuracy of a finite difference method
  • Write down the theta method.
  • For which theta is this method explicit?
  • For which theta is this method unconditionally stable?
  • For which theta is this method second-order accurate?
  • Derive the local truncation error
  • Is (*) finite difference method stable?
  • Show (*) is stable using Fourier analysis
  • Does (*) method have a maximum principle?
  • Show (*) converges globally using a maximum principle.
  • Are (*) boundary conditions Dirichlet? Neumann? Robin?
  • Compute one step with method (*).

[3] M&M Parabolic in higher dimensions

  • What is the ADI method?
  • How stable/accurate/expensive is the ADI method?
  • How does the ADI method compare to Crank Nicolson?
  • How does the Explicit method compare to ADI and Crank Nicolson?
  • Write down a finite difference approximation at a curved boundary.
  • Compute the stability condition for method (*) using Fourier
  • How sparse is the linear system solve for ADI and Crank Nicolson?

[4] M&M Hyperbolic Problems

  • What is the upwind method for a quasilinear advection equation?
  • How about the Lax-Wendroff method?
  • What are the characteristics?
  • What is the Courant-Friedrich-Lewy (CFL) condition?
  • What is the domain of dependence?
  • Compute the stability condition of (*) using Fourier
  • What happens when characteristics cross?
  • Write (*) PDE in conservation form.
  • What equation does the weak solution satisfy?
  • What is the shock speed for the weak solution?

[6] M&M Elliptic Problems

  • Write down a finite difference method for Laplace/Poisson
  • What is the local order of accuracy of (*) method?
  • What is the sparse structure of the system of equations?
  • Prove global convergence for centered difference
    for Poisson on a square domain with Dirichlet boundary conditions.
  • For a general elliptic problem, what four conditions must be satisfied to prove convergence using Theorem 6.1?
  • What is the global accuracy with curved boundaries (without proof)?
  • What about Neumann boundary conditions (without proof)?

[1] B Weak Formulation I

  • What is a functional?
  • What is a vector space? Is (*) a vector space?
  • What is an inner product? Is (*) an inner product?
  • What is the Cauchy-Schwarz inequality?
  • What is a norm? Is (*) a norm?
  • What is complete vector space?
  • Which vector spaces are complete?
  • Is C(k) complete?
  • Is H(k) complete?
  • What is a Hilbert Space? Give an example of a Hilbert Space.
  • What is L2?
  • What is H(k)?
  • Compute the L2-norm and inner-product of (*).
  • Compute the H(k)-norm and inner-product of (*).
  • Apply the Poincare-Friedrichs inequality.
  • What is a quadratic functional?
  • What is a stationary point?
  • Compute the directional derivative of (*) functional
  • What are the conditions for Lax-Milgram?
  • State the Riesz representation theorem.
  • Is (*) a bounded linear functional?
  • Is (*) a bounded and coercive bilinear form?
  • Why is Lax-Milgram so important?

[2] B Weak Formulation II

  • Derive the weak form of (*) in strong form
  • Derive the Euler-Lagrange equations for (*) functional
  • What is the Gauss divergence theorem?
  • Integrate the 2d/3d integral (*) by parts to get the weak form.
  • How do boundary conditions in the minimization form translate to boundary conditions in the strong form?
  • Which boundary conditions are "natural" in minimization form?
  • Which boundary conditions are "essential"?
  • Show that (*) satisfies the conditions for Lax-Milgram.
  • Is (*) domain Lipschitz? Does (*) satisify the cone condition?
  • What is the trace theorem?

[3] B Ritz-Galerkin Method

  • What is a(u,v) = G(v) in minimization form?
  • What is a(u,v) and G(v) for (*) in strong form?
  • Given a finite subspace with basis functions, derive the discrete equations for a(u,v) = G(v).
  • Show how to handle non-homogeneous boundary conditions.
  • What are the piecewise linear basis functions on a triangle?
  • Construct the mapping to a standard triangle.
  • Outline how you would assemble the global system of equations.
  • When is numerical integration necessary?
  • Apply a simple quadrature rule.

[4] B Error Estimates

  • Is (*) a conforming mesh?
  • Is (*) a uniform mesh?
  • What is the diameter of (*)?
  • Is (*) shape regular?
  • Are C(k-1) finite elements in H(k)?
  • What does Céa's Lemma tell us?
  • Show the finite element approximation is bounded
  • How accurate are H(k) finite elements?

[5] B Iterative Methods

  • Write down the non-linear weak form for (*).
  • Write down the linearized bilinear form for (*).
  • What would you solve to take one step of Newton's method?
  • When does the iteration M x(k+1) = N(k) + b converge?
  • Take one step of Jacobi/Gauss-Seidel for a 2 x 2 problem.
  • Is (*) diagonally dominant?
  • How many steps does it take for CG to converge?
  • Why is Jacobi and Gauss-Seidel so slow for many large problems?
  • How does Multigrid smooth error on all frequencies?

Last Updated: 27-Apr-08
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