Aerodynamic investigation of the Cour's pollen filter

At the Department of Physical Geography, Goteborg University, the Cour's po llen filter was used to calculate the aerial mass flow and concentration of marine salts in coastal and inland locations. During this work, it became apparent that a correction formula for obtaining the how through the filter was required. This was obtained by acquiring correct concentration values from the flow through an undisturbed, equally-sized cross section beside th e filter. Cour (1974) suggests that concentration values should be multipli ed by a factor of five but also adds that the relation is wind speed depend ant. Hence, an aerodynamic investigation was performed in a wind tunnel at five different reference wind speeds. The air flow through the filter was t hus found to depend on reference wind speed as a 4th grade polynomial. The airflow through the filter is insignificantly affected by applied contamina tion of wheat flour or pollen grains to the filter surface up to approximat ely 500 mg. Above is an increasing risk for reduced flow. The reduction can be estimated using the results of this work. Applying the correction to ex isting data showed that the correction effect decreases with increasing ref erence wind speed. Due to the form of the polynomial, a correction is not r ecommended outside the approximate interval 2 < u(ref) > 27 m s(-1).