TVD
 

Hi,

I am wondering why it is when people are implementing TVD schemes for bounded variables like the mixture fraction in Combusting flows, why is it that they use the TVD criteria for the spatial derivatives, but often times not for the time derivatives? Surely this can still result in an unbounded solution? I have seen people to use Crank-Nicolson and Three Point Backward differences which are not TVD as well the 3rd order Runge-Kutta scheme (used by Osher) which is TVD. Can anyone explain this to me?