  A novel set of wind tunnel measurements of the drag force and its spatial
distribution along aligned arrays of cubes of height H and planar area index
lambdap (air gap between cubes) equal to 0.028 (5H) to 0.69 (0.2H) is presented
and analysed. Two different types of measurements are compared: one type where
the drag force is obtained using the standard load cell method, another type
where the drag force is estimated by measuring the pressure difference between
windward and the leeward facades. Results show that the drag force is nearly
uniformly distributed for lower lambdap (0.028 and 0.0625), it decreases up to
50% at the second row for lambdap=0.11, and it sharply decreases for larger
lambdap (from 0.25 to 0.69) where the force mostly acts on the first row. It
follows that for the lowest lambdap the drag force typically formulated as a
drag area corresponds to the total frontal area of the array, whereas for large
lambdap the drag area corresponds to the area of the first row. By assessing
the driving pressure for ventilation from the drag force, the analysis is
extended to estimate the cross ventilation as an example of application of this
type of measurements.
