Mercurial > repos > public > sbplib
diff +rv/+time/BDFDerivative.m @ 1013:eb441fbdf379 feature/advectionRV
Draft implementation of RungeKutta with exterior RV updates
- Draft class RungeKuttaExteriorRV which updates the residual using a BDF approximation of the derivtive outside of the RK stages.
- Draft class for BDF derivative
| author | Vidar Stiernström <vidar.stiernstrom@it.uu.se> |
|---|---|
| date | Wed, 05 Dec 2018 15:04:44 +0100 |
| parents | |
| children | e547794a9407 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/+rv/+time/BDFDerivative.m Wed Dec 05 15:04:44 2018 +0100 @@ -0,0 +1,33 @@ +class BDFDerivative < handle + properties + dt + coefficents + end + methods + function obj = BDFDerivative(order, dt) + obj.coefficents = obj.getBDFCoefficients(order); + obj.dt = dt; + end + + function DvDt = evaluate(v, v_prev) + DvDt = (obj.coefficients(1)*v - sum(obj.coefficients(2:end).*v_prev),2)/obj.dt; + end + + function c = getBDFCoefficients(obj, order) + switch order + case 1 + c(1,1) = 1; c(1,2) = 1; + case 2 + c(1,1) = 3/2; c(1,2) = 4/2; c(1,3) = -1/2; + case 3 + c(1,1) = 11/6; c(1,2) = 18/6; c(1,3) = -9/6; c(1,4) = 2/6; + case 4 + c(1,1) = 25/12; c(1,2) = 48/12; c(1,3) = -36/12; c(1,4) = 16/12; c(1,5) = -3/12; + case 5 + c(1,1) = 137/60; c(1,2) = 300/60; c(1,3) = -300/60; c(1,4) = 200/60; c(1,5) = -75/60; c(1,6) = 12/60; + case 6 + c(1,1) = 147/60; c(1,2) = 360/60; c(1,3) = -450/60; c(1,4) = 400/60; c(1,5) = -225/60; c(1,6) = 72/60; c(1,7) = -10/60; + assert(length(c) == (order+1)); + end + end +end