If you assume that the divergence angle of the cone is relatively small and that the flow is relatively incompressible, you can approximate the downward velocity component as roughly uniformly distributed, and, from the continuity equation, you can then solve for the radial velocity component at each cross section. You can then estimate the magnitude of the velocity at the center and at the edge, just above the layer of filters. Using Bernoulli, this will enable you to determine the difference in pressure between the center and edge. The result you get for the pressure difference will be proportional to the stagnation pressure, multiplied by the square of the rate of change of radius with height. The flow non-uniformity through the layer of filters will be equal to this pressure difference divided by the pressure drop across the layer of filters. If you want to crudely bound this answer, just make the pressure drop across the layer of filters large compared to the stagnation pressure.

If you assume that the divergence angle of the cone is relatively small and that the flow is relatively incompressible, you can approximate the downward velocity component as roughly uniformly distributed, and, from the continuity equation, you can then solve for the radial velocity component at each cross section. You can then estimate the magnitude of the velocity at the center and at the edge, just above the layer of filters. Using Bernoulli, this will enable you to determine the difference in pressure between the center and edge. The result you get for the pressure difference will be proportional to the dynamic pressure, multiplied by the square of the rate of change of radius with height. The flow non-uniformity through the layer of filters will be equal to this pressure difference divided by the pressure drop across the layer of filters. If you want to crudely bound this answer, just make the pressure drop across the layer of filters large compared to the dynamic pressure.