Givem the temperature, the dimensions of the filter bed, the physics and granulometric characteristics of its media and the washing water velocity , calculates the percentual expansion of the media ant its expanded depth.
References
AMIRTHARAJAH, A; CLEASBY, J. L. Predicting expansion of filters during backwash. Journal AWWA, v. 64, n. 1, p. 52-9, jan. 1972.