If I want to know the airflow for the same computational mesh with a different inflow wind speed, do I have to redo the whole simulation from the start?

If the airflow is within the range applicable for the similarity rule, in other words, if the order of the Reynolds number does not change, you can use the wind speed ratio to make a conversion from the simulation results for one case, in order to use them as the wind speed distribution for a different wind speed grade. The conversion is calculated automatically by configuring the ground height and wind speed to be used as standard. This is done when converting the calculation results into NetCDF format.