PDE Toolbox - Convection in Diffusion Equation

I'm trying to add a convection term to solve a diffusion PDE using the PDE Toolbox. I'm defining the PDE as:

specifyCoefficients(model,'Face',2,'m',0,'d',1,'c',Da,'a',0,'f',@fcoeff);

and have the following at the end of my code:

function f = fcoeff(location,state)
y = location.y./h;
x = location.x./L;
v = va;
f = -(v.*state.ux.*state.time + v.*state.uy.*state.time);
end

However, whenever I try to run the code I get the following error:

Error using pde.CoefficientAssignment/checkCoefFcnHdlArgCounts (line 499)
Function specifying a coefficient must accept two
input arguments and return one output argument.

Error in pde.CoefficientAssignment/checkFcnHdlArgCounts (line 272)
            self.checkCoefFcnHdlArgCounts(self.f, systemsize, ndims);

Error in pde.CoefficientAssignment (line 104)
      obj.checkFcnHdlArgCounts(systemsize, numdims);

Error in pde.PDEModel/specifyCoefficients (line 143)
        coef = pde.CoefficientAssignment(self.EquationCoefficients,argsToPass{:});

Error in Dry_Air (line 49)
specifyCoefficients(model,'Face',2,'m',0,'d',1,'c',Da,'a',0,'f',@fcoeff);

I don't understand the error because as I see it I am ipnuting two arguments and am returning one output. Whenever I take away the function for 'f' on the RHS of the PDE my code works perfectly. Any help would be much appreciated!

Answer 1

[Ravi Kumar]

It looks like your function errored without returning one onput. Most likely the error could have been due to 'va' being out of scope for the function fcoeff.

Regards,

Ravi

[Andrew Ferguson]

Even if I change the function to

function f = fcoeff(location,state)
y = location.y./h;
x = location.x./L;
va = 0.5; % m/s
v = va;
f = -(v.*state.ux.*state.time + v.*state.uy.*state.time);
end

I still get the same error. Any other thoughts?

[Ravi Kumar]

I think you are still missing some variable in the funciton, like 'h' and 'L'. You can also insert a breakpoint on the first line of the funciton and see where you get the error.

Regards,

Ravi

[Andrew Ferguson]

Thanks! Adding in h and L worked!

[Gobinda Debnath]

Hello Andrew ferguson and ravi sir, i am new to matlab, can i get a sample code for convection-diffusion term equation, in matlab how to handle convection term, please help me on this, thank you