Hi I need to model variable flow rate with time depending on the temperature on the particular patch.
If Temp<300.15 K then flow rate is 0.058;
else Temp>300.15K then flow rate is (m*temp)+c

I recently read that expressions can be modelled directly in openfoam 1912.
Initially I tried to model flowrate I'm unable to do so. Hence I used
SERVER_SOURCE
{
type exprFixedValue;
value $internalField;
valueExpr "(tSink<=300.15)?vector(0,value1/area1,0):vector(0,((0.00531*tSink)-0.08485)/area1,0)";
variables
(
"tSink{SERVER_SINK} = weightAverage(T)"
"value1{SERVER_SOURCE} = 0.05852"
"area1{SERVER_SOURCE} = area()"
);
}
But Im getting the following warning while the simulation is running
"--> FOAM Warning :
From function bool Foam::expressions::exprResult::getUniformChecked(F oam::expressions::exprResult&, Foam::label, bool, bool) const [with Type = double; Foam::label = int]
in file expressions/exprResult/exprResultI.H at line 143
Different min/max values: (0.000674827 0.00410428) Using the average 0.00146216
Can any one explain how to fix this error?

Also is it feasible to model variable flow rate instead of velocity?