Error in ODE15s

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Ranjeev Kumar Bhatia 2021-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/835258-error-in-ode15s

评论： Ranjeev Kumar Bhatia 2021-5-23

Richards.m

I am trying to solve Richards equation for 1D soil column. All the state variables are vectorized. and the functions are defined below the main body of the code. Since the ode is of the form M(t,y)*dy/dt = f(t,y). We can define M(t,y) using the ode options structure i.e. options =odeset('RelTol',1e-6,'AbsTol',1e-6,'Mass',@(t,hw) Richardmass(t,hw,soilPar,modPar), 'MStateDependence','strong').

when I Include the options structure in ode15s solver I get an error saying :-

' Warning: Failure at t=5.661773e+00. Unable to meet integration tolerances without reducing the step size below the

smallest value allowed (1.421085e-14) at time t.

In ode15s (line 655)

In Richards (line 93) '

but without the mass matrix i get a solution but it is not correct

In the code given the variables are t and hw ( time and pressure head) , soilPar and modPar are structures containing the soil properties and model properties repsectively. A staggeredgrid approach was used to deinfe the model parameters

Any hep woul dbe greatky appreciated, Thanks in Advance . :-)

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Answer 1

Jan 2021-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/835258-error-in-ode15s#answer_704593

Reduce tspan to tspan = [0, 0.0023] and check the results. It seems, like the values implode such that the integration must fail. I'd assume a typo in the fomula.