11using Test
2- using DiffEqOperators, OrdinaryDiffEq
2+ using DiffEqOperators, OrdinaryDiffEq, LinearAlgebra
33
44@testset " KdV equation (Single Solition)" begin
55 N = 21
@@ -9,26 +9,28 @@ using DiffEqOperators, OrdinaryDiffEq
99 # x = 10:Δx:30;
1010 x = - 10 : Δx: 10 ;
1111 # ϕ(x,t) = (r/2)*sech.((sqrt(r)*(x-r*t)/2)-7).^2 # solution of the single forward moving wave
12- ϕ (x,t) = (1 / 2 )* sech .((x- t)/ 2 ).^ 2 # solution of the single forward moving wave
12+ ϕ (x,t) = (1 / 2 )* sech .((x .- t)/ 2 ).^ 2 # solution of the single forward moving wave
1313
1414 u0 = ϕ (x,0 );
1515 oriu = zeros (size (x));
1616
17- const du3 = zeros (size (x));
18- const temp = zeros (size (x));
17+ # const du3 = zeros(size(x));
18+ du = zeros (size (x));
19+ # const temp = zeros(size(x));
1920
2021 # A = CenteredDifference(1,2,Δx,length(x),:Dirichlet0,:Dirichlet0);
21- A = UpwindOperator {Float64} (1 ,3 ,Δx,length (x),true .| BitVector (undef,length (x)),
22- :Dirichlet0 ,:Dirichlet0 );
22+ A = UpwindDifference {Float64} (1 ,3 ,Δx,length (x),- 1 );
2323 # C = CenteredDifference(3,2,Δx,length(x),:Dirichlet0,:Dirichlet0);
24- C = UpwindOperator {Float64} (3 ,3 ,Δx,length (x),true .| BitVector (undef,length (x)),
25- :Dirichlet0 ,:Dirichlet0 );
24+ # C = UpwindDifference{Float64}(3,3,Δx,length(x),-1);
2625
2726 function KdV (du, u, p, t)
28- C (t,u,du3)
29- A (t,u,du)
30- @. temp = - 0.5 * u* du - 0.25 * du3
31- copyto! (du,temp)
27+ # bc = DirichletBC(ϕ(-10-Δx,t),ϕ(10+Δx,t))
28+ bc = GeneralBC ([0 ,1 ,- 6 * ϕ (- 10 ,t),0 ,- 1 ],[0 ,1 ,- 6 * ϕ (10 ,t),0 ,- 1 ],Δx,3 )
29+ # mul!(du3,C,bc*u)
30+ mul! (du,A,bc* u)
31+ # @. temp = -0.5*u*du - 0.25*du3
32+ # copyto!(du,temp)
33+
3234 end
3335
3436 single_solition = ODEProblem (KdV, u0, (0. ,5. ));
@@ -41,13 +43,14 @@ using DiffEqOperators, OrdinaryDiffEq
4143 =#
4244
4345 for t in 0 : 0.5 : 5
44- @test_skip soln (t) ≈ ϕ (x,t) atol = 0.01 ;
46+ @test soln (t) ≈ ϕ (x,t) atol = 0.01 ;
4547 end
4648end
4749
4850# Conduct interesting experiments by referring to
4951# http://lie.math.brocku.ca/~sanco/solitons/kdv_solitons.php
50- @testset " KdV equation (Double Solition)" begin
52+ # TODO The true solution for this case seems unstable, look for a workaround
53+ #= @testset "KdV equation (Double Solition)" begin
5154 N = 10
5255 Δx = 1/(N-1)
5356
5760
5861 function ϕ(x,t)
5962 # t = t-10
60- num1 = 2 (c1- c2)* (c1* cosh .(√ c2* (x- c2* t)/ 2 ).^ 2 + c2* sinh .(√ c1* (x- c1* t)/ 2 ).^ 2 )
61- den11 = (√ c1-√ c2)* cosh .((√ c1* (x- c1* t) + √ c2* (x- c2* t))/ 2 )
62- den12 = (√ c1+√ c2)* cosh .((√ c1* (x- c1* t) - √ c2* (x- c2* t))/ 2 )
63+ num1 = 2(c1-c2)*(c1*cosh.(√c2*(x .- c2*t)/2).^2 + c2*sinh.(√c1*(x .- c1*t)/2).^2)
64+ den11 = (√c1-√c2)*cosh.((√c1*(x .- c1*t) + √c2*(x .- c2*t))/2)
65+ den12 = (√c1+√c2)*cosh.((√c1*(x .- c1*t) - √c2*(x .- c2*t))/2)
6366 den1 = (den11+den12).^2
6467 return num1./den1
6568 end
6669
67- const du3 = zeros (x);
68- const temp = zeros (x);
70+ # const du3 = zeros(size(x));
71+ du = zeros(size(x));
72+ # const temp = zeros(size(x));
6973
70- A = UpwindOperator {Float64} (1 ,1 ,Δx,length (x),false .* BitVector (length (x)),
71- :Dirichlet0 ,:nothing );
72- C = UpwindOperator {Float64} (3 ,1 ,Δx,length (x),false .* BitVector (length (x)),
73- :Dirichlet0 ,:nothing );
74+ A = UpwindDifference{Float64}(1,3,Δx,length(x),-1);
75+
76+ # C = UpwindDifference{Float64}(3,1,Δx,length(x),-1);
7477
7578 function KdV(du, u, p, t)
76- C (t,u,du3)
77- A (t, u, du)
78- @. temp = - 6 * u* du - du3
79- copyto! (du,temp)
79+ bc = GeneralBC([0,1,-6*ϕ(-50,t),0,-1],[0,1,-6*ϕ(50,t),0,-1],Δx,3)
80+ # mul!(du3,C,bc*u)
81+ mul!(du,A,bc*u)
82+ # @. temp = -6*u*du - du3
83+ # copyto!(du,temp)
8084 end
8185
8286 u0 = ϕ(x,0);
8589
8690 # The solution is a forward moving soliton wave with speed = 1
8791 for t in 0:0.1:9
88- @test_skip soln (t) ≈ ϕ (x,t)
92+ @test_skip soln(t) ≈ ϕ(x,t) atol = 0.01
8993 end
90- end
94+ end =#
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