value is then multi-dimensional, as for instance shown in:
# Define velocity field
class uExactDef(UserExpression):
def __init__(self, t, **kwargs):
super().__init__(kwargs)
self._t = t
def eval_cell(self, value, x, ufc_cell):
value[0] = -self._t(x) * np.sin(2 * np.pi * (1 - x[1]))
value[1] = Constant(0.0)
def value_shape(self):
return (2,)
as shown in: Same time dependent temperature problem in two different ways: one works, one doesn't. Why?