ارجو المساعده في فهم قيمه ال P الموجودة في المعادله و معرفه قيمتها لكل طبقه و اذا كانت هناك جداول مستخدمه لهذا الغرض مع العلم انها مهمهة جدا في حسابات ال headloss في الrapid sand filter
وهذا هو الملخص اللذي وجدته عن تصميم الفلتر
ارجو المساعدة و بسرعه
و الشكر الجزيل علي تعاونكم

Clean Water Headloss
Several equations have been developed to describe the flow of clean water through a porous medium. Carman-Kozeny equation used to calculate head loss is as follows:
h= f (1-a)Lvs2
fa3dg
h= f p(1-a)Lvs2
fa3dgg
f =150
(1-a) + 1.75
Ng
Ng=
fdvsr
m
where, h = headloss, m
f = friction factor
a = porosity
f = particle shape factor (1.0 for spheres, 0.82 for rounded sand, 0.75 for average sand,0.73 for crushed coal and angular sand)
L = depth of filter bed or layer, m
d = grain size diameter, m
vs = superficial (approach) filtration velocity, m/s
g = accelaration due to gravity, 9.81 m/s2
p = fraction of particles ( based on mass) within adjacent sieve sizes
dg = geometric mean diameter between sieve sizes d1 and d2
Ng = Reynolds number
m = viscosity, N-s/m2