Bed materials

n₁

n₂

n₃

$\propto$

Min Z (m²)

d₅₀ = 25 mm

0.032

0.016

0.018

1.42

1.16 × 10⁻⁴

d₅₀ = 8 mm

0.028

0.016

0.018

1.46

1.62 × 10⁻⁴

Lined concrete

0.027

0.015

0.017

1.48

1.09 × 10⁻⁴