Hello,

I would like to define the exact solution for a time dependent stokes problem. I used to use Expression in fenics to do this. How can I define a vector valued function in fenicsx?

I have written the following code but it does not work

class exact_solution1():

def **init**(self):

self.t = 0.0

def eval(self, x):

print(x.shape[1])

t = self.t

return np.full(x.shape[1], (pow(t,2)*(pow(x[0],4)-2*pow(x[0],3)+ pow(x[0],2))*(4*pow(x[1],3)-6*pow(x[1],2)+ 2*x[1]), -pow(t,2)*(pow(x[1],4)-2*pow(x[1],3)+ pow(x[1],2))*(4*pow(x[0],3)-6*pow(x[0],2)+ 2*x[0])))

I would be grateful if someone can help me with this!

Thank you in advance!

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