Hydrodynamic calculation Butterfly valve double disc

Butterfly valve (double disc) D s +F by +F bx +M H L 0.5D D Q max +F y +F x +F Φ Q air α 0.2D 0.4D c D s L D
Butterfly valve (double disc)
Double disc c D s L D
Double disc

Values for calculation

$D$ $\mathrm{mm}$
$L_D$ $\mathrm{mm}$
$c$ $\mathrm{mm}$
$D_s$ $\mathrm{mm}$
$Q_{max}$ $\mathrm{m^3/s}$
$H$ $\mathrm{m}$
$g$ $\mathrm{m/s^2}$
$T$ $\mathrm{°C}$
$ρ$ $\mathrm{kg/m^3}$
$P_T$ $\mathrm{Pa}$
$ΔP$ $\mathrm{m}$
$h$ $\mathrm{m}$
$ρ_{air}$ $\mathrm{kg/m^3}$
$p_{a}$ $\mathrm{Pa}$
$t$ $\mathrm{s}$
$L$ $\mathrm{m}$


Velocity in valve

$$v_{max}=\cfrac{4\cdot 10^6\cdot Q_{max}}{π\cdot D^2}$$

Theoretical pressure in the valve at full opening

$$Δ_h=\cfrac{v_{max}^2}{2\cdot g}\cdot \left(ζ+1\right)$$

Pressure parameter

$$p=\cfrac{Δ_h}{H}$$$$0 < p \le 1$$

Effective closing time factor

$$c_{ef}=0$$$$c_{ef}\le 1$$

Under-pressure behind the valve

$$P_{u}=\max\left(-\cfrac{L\cdot v_{max}}{g\cdot t\cdot c_{ef}}, -10\right)$$