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Introduce abstractions for TVD slope limiter functions (Durran 1999) and
van Leer limiters as in Lin(1994) Update numerical flux stencils to use tvd limiters Update column examples and references Update deformation flow example to use limiters Co-authored-by: Charles Kawczynski <[email protected]>
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using Test | ||
using LinearAlgebra | ||
import ClimaComms | ||
ClimaComms.@import_required_backends | ||
using OrdinaryDiffEqSSPRK: ODEProblem, solve, SSPRK33 | ||
using ClimaTimeSteppers | ||
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||
import ClimaCore: | ||
Fields, | ||
Domains, | ||
Topologies, | ||
Meshes, | ||
DataLayouts, | ||
Operators, | ||
Geometry, | ||
Spaces | ||
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||
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# Advection Equation, with constant advective velocity (so advection form = flux form) | ||
# ∂_t y + w ∂_z y = 0 | ||
# the solution translates to the right at speed w, | ||
# so at time t, the solution is y(z - w * t) | ||
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||
# visualization artifacts | ||
ENV["GKSwstype"] = "nul" | ||
using ClimaCorePlots, Plots | ||
Plots.GRBackend() | ||
dir = "tvd_advection" | ||
path = joinpath(@__DIR__, "output", dir) | ||
mkpath(path) | ||
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function tendency!(yₜ, y, parameters, t) | ||
(; w, Δt, limiter_method) = parameters | ||
FT = Spaces.undertype(axes(y.q)) | ||
bcvel = pulse(-π, t, z₀, zₕ, z₁) | ||
divf2c = Operators.DivergenceF2C( | ||
bottom = Operators.SetValue(Geometry.WVector(FT(0))), | ||
top = Operators.SetValue(Geometry.WVector(FT(0))), | ||
) | ||
upwind1 = Operators.UpwindBiasedProductC2F( | ||
bottom = Operators.Extrapolate(), | ||
top = Operators.Extrapolate(), | ||
) | ||
upwind3 = Operators.Upwind3rdOrderBiasedProductC2F( | ||
bottom = Operators.ThirdOrderOneSided(), | ||
top = Operators.ThirdOrderOneSided(), | ||
) | ||
FCTZalesak = Operators.FCTZalesak( | ||
bottom = Operators.FirstOrderOneSided(), | ||
top = Operators.FirstOrderOneSided(), | ||
) | ||
TVDSlopeLimited = Operators.TVDSlopeLimitedFlux( | ||
bottom = Operators.FirstOrderOneSided(), | ||
top = Operators.FirstOrderOneSided(), | ||
method = limiter_method, | ||
) | ||
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If = Operators.InterpolateC2F() | ||
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if limiter_method == "Zalesak" | ||
@. yₜ.q = | ||
-divf2c( | ||
upwind1(w, y.q) + FCTZalesak( | ||
upwind3(w, y.q) - upwind1(w, y.q), | ||
y.q / Δt, | ||
y.q / Δt - divf2c(upwind1(w, y.q)), | ||
), | ||
) | ||
else | ||
Δfluxₕ = @. w * If(y.q) | ||
Δfluxₗ = @. upwind1(w, y.q) | ||
@. yₜ.q = | ||
-divf2c( | ||
upwind1(w, y.q) + | ||
TVDSlopeLimited(upwind3(w, y.q) - upwind1(w, y.q), y.q / Δt, w), | ||
) | ||
end | ||
end | ||
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# Define a pulse wave or square wave | ||
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||
FT = Float64 | ||
t₀ = FT(0.0) | ||
t₁ = FT(6) | ||
z₀ = FT(0.0) | ||
zₕ = FT(2π) | ||
z₁ = FT(1.0) | ||
speed = FT(-1.0) | ||
pulse(z, t, z₀, zₕ, z₁) = abs(z - speed * t) ≤ zₕ ? z₁ : z₀ | ||
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n = 2 .^ 8 | ||
elemlist = 2 .^ [3, 4, 5, 6, 7, 8, 9, 10] | ||
Δt = FT(0.3) * (20π / n) | ||
@info "Timestep Δt[s]: $(Δt)" | ||
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domain = Domains.IntervalDomain( | ||
Geometry.ZPoint{FT}(-10π), | ||
Geometry.ZPoint{FT}(10π); | ||
boundary_names = (:bottom, :top), | ||
) | ||
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stretch_fns = [Meshes.Uniform()] | ||
plot_string = ["uniform"] | ||
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for (i, stretch_fn) in enumerate(stretch_fns) | ||
limiter_methods = ( | ||
Operators.RZeroLimiter(), | ||
Operators.RMaxLimiter(), | ||
Operators.KorenLimiter(), | ||
Operators.SuperbeeLimiter(), | ||
Operators.MonotonizedCentralLimiter(), | ||
"Zalesak", | ||
) | ||
for (j, limiter_method) in enumerate(limiter_methods) | ||
@info (limiter_method, stretch_fn) | ||
mesh = Meshes.IntervalMesh(domain, stretch_fn; nelems = n) | ||
cent_space = Spaces.CenterFiniteDifferenceSpace(mesh) | ||
face_space = Spaces.FaceFiniteDifferenceSpace(cent_space) | ||
z = Fields.coordinate_field(cent_space).z | ||
O = ones(FT, face_space) | ||
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# Initial condition | ||
q_init = pulse.(z, 0.0, z₀, zₕ, z₁) | ||
y = Fields.FieldVector(q = q_init) | ||
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# Unitary, constant advective velocity | ||
w = Geometry.WVector.(speed .* O) | ||
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# Solve the ODE | ||
parameters = (; w, Δt, limiter_method) | ||
prob = ODEProblem( | ||
ClimaODEFunction(; T_exp! = tendency!), | ||
y, | ||
(t₀, t₁), | ||
parameters, | ||
) | ||
sol = solve( | ||
prob, | ||
ExplicitAlgorithm(SSP33ShuOsher()), | ||
dt = Δt, | ||
saveat = Δt, | ||
) | ||
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q_final = sol.u[end].q | ||
q_analytic = pulse.(z, t₁, z₀, zₕ, z₁) | ||
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err = norm(q_final .- q_analytic) | ||
rel_mass_err = norm((sum(q_final) - sum(q_init)) / sum(q_init)) | ||
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if j == 1 | ||
fig = Plots.plot(q_analytic; label = "Exact", color = :red) | ||
end | ||
linstyl = [:dash, :dot, :dashdot, :dashdotdot, :dash, :solid] | ||
clrs = [:orange, :gray, :green, :maroon, :pink, :blue] | ||
if limiter_method == "Zalesak" | ||
fig = plot!( | ||
q_final; | ||
label = "Zalesak", | ||
linestyle = linstyl[j], | ||
color = clrs[j], | ||
dpi = 400, | ||
xlim = (-0.5, 1.1), | ||
ylim = (-15, 10), | ||
) | ||
else | ||
fig = plot!( | ||
q_final; | ||
label = "$(typeof(limiter_method))"[21:end], | ||
linestyle = linstyl[j], | ||
color = clrs[j], | ||
dpi = 400, | ||
xlim = (-0.5, 1.1), | ||
ylim = (-15, 10), | ||
) | ||
end | ||
fig = plot!(legend = :outerbottom, legendcolumns = 2) | ||
if j == length(limiter_methods) | ||
Plots.png( | ||
fig, | ||
joinpath( | ||
path, | ||
"SlopeLimitedFluxSolution_" * | ||
"$(typeof(limiter_method))"[21:end] * | ||
".png", | ||
), | ||
) | ||
end | ||
@test err ≤ 0.25 | ||
@test rel_mass_err ≤ 10eps() | ||
end | ||
end |
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