Hello Anhvu lee,
1) For the porous zone settings I recommend you to check the default setting of relative velocity resisitance formulation . An alternate way to calculate the viscous resistance is Darcy porous media law where it states that the pressure drop is directly proportional to velocity and the inertial term of pressure drop equation can be considered to be zero. but this is applicable only for laminar fows.
So in such cases the viscous resisitance can be calculated by
I am attaching the user guide link . Kindly refer this 3.4.7 user guide link of cell zone conditions to understand how the porous settings are given.
2)In source term set the momentum in particualr direction as source by multiplying the mass*velocity of the fluid.
3)By setting specific dissipation rate option you can simulate the hourly equivalent evatranspiration.
I am attaching the screenshots for your reference.
I hope this helps you in your simulation.