Algorithm 1: Mannshardt's transition scheme (uniform time steps) |
Given $ \tau,t_0,\mathit{\boldsymbol{x}}_0 $. |
for $ k=0,1,2,\dots $ do |
end |
We introduce conservative integrators for long term integration of piecewise smooth systems with transversal dynamics and piecewise smooth conserved quantities. In essence, for a piecewise dynamical system with piecewise defined conserved quantities where its trajectories cross transversally to its interface, we combine Mannshardt's transition scheme and the Discrete Multiplier Method to obtain conservative integrators capable of preserving conserved quantities up to machine precision and accuracy order. We prove that the order of accuracy of the conservative integrators is preserved after crossing the interface in the case of codimension one number of conserved quantities. Numerical examples in two and three dimensions illustrate the preservation of accuracy order across the interface for cubic and logarithmic type conserved quantities. We observed that conservative transition schemes can prevent spurious transitions from occurring, even in the case when there are fewer conserved quantities.
Citation: |
Figure 4. (A) An initial condition of $ [0.612, 0.0137, 0.629] $ was used with a final time $ T = 700 $ and step size $ \tau = 0.07 $. Here DMM transition scheme agrees with the RK4 transition scheme, but the RK2 transition scheme has drifted far away due to spurious transitions. (B) Convergence of the error between the exact transition time $ t^* $ and the approximate transition time $ \hat{t} $ for the PWS three species Lotka-Volterra system
Figure 7. The sign of the switching function $ g $ for the three methods are plotted versus time, corresponding tok__ge Figure 6. In this case, the solution computed using RK2 makes spurious transitions (denoted by red "x") while the RK4 and DMM solutions do not
Figure 9. The sign of the switching function $ g $ for the three methods are plotted versus time, corresponding to Figure 8. All three methods make initial transitions and then RK2 makes further spurious transitions (denoted by red "x")
Table .
Algorithm 1: Mannshardt's transition scheme (uniform time steps) |
Given $ \tau,t_0,\mathit{\boldsymbol{x}}_0 $. |
for $ k=0,1,2,\dots $ do |
end |
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(A) PWS trajectories for the elliptic curve example with the interface being a circle of radius 1 centered at the origin. (B) Convergence of the error between the exact transition time
Comparison of error in the solution of the PWS elliptic curve system with different perturbation added to
Comparison of the error in conserved quantity versus time between our DMM transition scheme and the RK2 transition scheme for the PWS elliptic curve system. An initial condition of
(A) An initial condition of
Comparison of error in the solution of the PWS three species Lotka-Volterra system with different perturbation added to
Comparison of the error in conserved quantity versus time, as computed by RK2 (top), RK4 (middle) and our DMM transition scheme (bottom) for the PWS three species Lotka-Voltera system
The sign of the switching function
Comparison of error in conserved quantity versus time, as computed by RK2 (top), RK4 (middle) and our DMM transition scheme (bottom) for the PWS three species Lotka-Voltera system when the solution makes several transitions
The sign of the switching function