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Hydrodynamic calculation Howell-Bunger valve

Howell-Bunger valve D 90° 48° R 72° S 25° 40° a b c e f g +F x
Howell-Bunger valve

Values for calculation

$D$ $\mathrm{mm}$
$S$ $\mathrm{mm}$
$R$ $\mathrm{mm}$
$a$ $\mathrm{mm}$
$b$ $\mathrm{mm}$
$c$ $\mathrm{mm}$
$e$ $\mathrm{mm}$
$f$ $\mathrm{mm}$
$g$ $\mathrm{mm}$
$H$ $\mathrm{m}$
$g$ $\mathrm{m/s^2}$
$T$ $\mathrm{°C}$
$ρ$ $\mathrm{kg/m^3}$
$P_{SV}$ $\mathrm{Pa}$
$n$
$ΔP$ $\mathrm{m}$
$Σζ$
$h$ $\mathrm{m}$
$ρ_{air}$ $\mathrm{kg/m^3}$
$p_{air}$ $\mathrm{Pa}$
$h_j$ $\mathrm{m}$
Hydraulic jump behind the valve - model no.1 D 2.5 D L 1 L 2 h l h j
Hydraulic jump behind the valve - model no.1
Dimensional sketch - model no.1 x D 1.25 D 1 D 45° 2.5 D 2.5 D 30° 3 D 6 D 0.4D 2.76D 0.39D 0.86D 1.36D 1.39D 2.77 D 3.08 D 45° P u P u P 1 u-air P 2 u-air P 1 u-air P 2 u-air
Dimensional sketch - model no.1
Hydraulic jump behind the valve - model no.2 D 2.5 D L 1 L 2 h l h j
Hydraulic jump behind the valve - model no.2
Dimensional sketch - model no.2 D 2.82 D 3.33 D 45° 1.36D 3 D 6 D 30° 0.39D 2.56D 1.94D 0.39D 0.58D 45° 0.64D 2.5 D 1.11D 0.6D 0.44 D 0.1 D 4.36D 1.5 D 1.5 D P u P u P 1 u-air P 1 u-air P 2 u-air P 2 u-air
Dimensional sketch - model no.2
Hydraulic jump behind the valve - model no.3 h l h j D 1.2 D L 1 L 2
Hydraulic jump behind the valve - model no.3
Dimensional sketch - model no.3 D 1.82 D 2.33 D 45° 1.36D 3 D 6 D 30° 0.39D 2.56D 1.94D 45° 1.2 D 1.11D 0.6D 0.1 D 4.36D 1.5 D 1.5 D P u P u P 1 u-air P 1 u-air P 2 u-air P 2 u-air
Dimensional sketch - model no.3

Calculation

Flow

$$Q_{max}=\cfrac{1}{\sqrt{1+Σζ+\min\left(ζ\right)}}\cdot\cfrac{π\cdot D^2}{4\cdot 10^6}\cdot\sqrt{2\cdot g\cdot H}$$

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

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

Pressure parameter

$$p=\cfrac{Δ_h}{H}$$

$$0 < p \le 1$$
Valve position
Flow coefficient
Coefficient of hydraulic force on body in the axis x
Loss coefficient
Reduced free flow area in the throttle control system
Relative flow
$S/D$ $K_Q$ $K_{bx}$ $ζ$ $f_r$ $Q_p$
$\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$
No data

$K_Q \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Flow coefficient

$K_{bx} \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Coefficient of hydraulic force on body in the axis x

$ζ \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Loss coefficient

$$ζ=\cfrac{1-K_Q^2}{K_Q^2}$$

$f_r \mathrm{[-]}$
$Q_p \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Coefficients

$$f_r=\cfrac{K_Q}{K_{Qmax}}$$
$$Q_p=\cfrac{f_r}{\sqrt{p+f_r^2\cdot \left(1-p\right)}}$$
Valve position
Flow of water in the pipeline
Water velocity in pipeline
Energy before the valve
$S/D$ $Q$ $v$ $T_x$
$\mathrm{ }$ $\mathrm{m^3/s}$ $\mathrm{m/s}$ $\mathrm{m}$
No data

$Q \mathrm{[m^3/s]}$
$v \mathrm{[m/s]}$
No data
$S/D\mathrm{[-]}$
Flow and speed of water in the pipeline

$$Q=Q_p\cdot Q_{max}$$
$$v=Q_p\cdot v_{max}$$

$T_x \mathrm{[m]}$
No data
$S/D\mathrm{[-]}$
Energy before the valve

$\text{if }\ \text{model }$$\text{number }$$\text{for }$$\text{Howell-Bunger }$$\text{valve}= 3$
$$T_x=H+\cfrac{v^2}{2\cdot g}+1.5\cdot \cfrac{D}{1000}-\cfrac{v^2}{2\cdot g}\cdot Σζ$$
$\text{else}$
$$T_x=H+\cfrac{v^2}{2\cdot g}+2.5\cdot \cfrac{D}{1000}-\cfrac{v^2}{2\cdot g}\cdot Σζ$$
Valve position
Coefficient of water level for $ \cfrac{T_x}{D}=10 $
Coefficient of water level for $ \cfrac{T_x}{D}=20 $
Coefficient of water level for $ \cfrac{T_x}{D}=30 $
Coefficient of water level for $ \cfrac{T_x}{D}=40 $
Coefficient of water level for $ \cfrac{T_x}{D}=50 $
Water level
$S/D$ $h_{l-10}$ $h_{l-20}$ $h_{l-30}$ $h_{l-40}$ $h_{l-50}$ $h_l$
$\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{m}$
No data

$h_{l-10} \mathrm{[-]}$
$h_{l-20} \mathrm{[-]}$
$h_{l-30} \mathrm{[-]}$
$h_{l-40} \mathrm{[-]}$
$h_{l-50} \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Coefficient of water level

$h_l \mathrm{[m]}$
No data
$S/D\mathrm{[-]}$
Water level

$\text{if }\ \cfrac{T_x\cdot 10^3}{D}< 10$
$$h_l=h_{l-10}\cdot\cfrac{D}{1000}$$
$\text{else if }\ \cfrac{T_x\cdot 10^3}{D}< 20$
$$h_l=h_{l-20}\cdot\cfrac{D}{1000}$$
$\text{else if }\ \cfrac{T_x\cdot 10^3}{D}< 30$
$$h_l=h_{l-30}\cdot\cfrac{D}{1000}$$
$\text{else if }\ \cfrac{T_x\cdot 10^3}{D}< 40$
$$h_l=h_{l-40}\cdot\cfrac{D}{1000}$$
$\text{else}$
$$h_l=h_{l-50}\cdot\cfrac{D}{1000}$$
Valve position
Coefficient of under-pressure for $ \cfrac{h_l}{D}=0 $
Coefficient of under-pressure for $ \cfrac{h_l}{D}=2 $
Coefficient of under-pressure for $ \cfrac{h_l}{D}=2.5 $
Coefficient of under-pressure for $ \cfrac{h_l}{D}=3 $
Coefficient of under-pressure for $ \cfrac{h_l}{D}=3.5 $
$S/D$ $K_{Pu-0}$ $K_{Pu-2}$ $K_{Pu-2.5}$ $K_{Pu-3}$ $K_{Pu-3.5}$
$\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$
No data

$K_{Pu-0} \mathrm{[-]}$
$K_{Pu-2} \mathrm{[-]}$
$K_{Pu-2.5} \mathrm{[-]}$
$K_{Pu-3} \mathrm{[-]}$
$K_{Pu-3.5} \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Coefficient of under-pressure for $ \cfrac{h_l}{D}=0\ \text{to}\ 3.5 $

Valve position
Coefficient of under-pressure for $ \cfrac{h_l}{D}=3.6 $
Coefficient of under-pressure for $ \cfrac{h_l}{D}=3.9 $
Coefficient of under-pressure for $ \cfrac{h_l}{D}=4 $
Coefficient of under-pressure for $ \cfrac{h_l}{D}=4.2 $
Coefficient of under-pressure for $ \cfrac{h_l}{D}=4.5 $
Coefficient of under-pressure for $ \cfrac{h_l}{D}=5 $
$S/D$ $K_{Pu-3.6}$ $K_{Pu-3.9}$ $K_{Pu-4}$ $K_{Pu-4.2}$ $K_{Pu-4.5}$ $K_{Pu-5}$
$\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$
No data

$K_{Pu-3.6} \mathrm{[-]}$
$K_{Pu-3.9} \mathrm{[-]}$
$K_{Pu-4} \mathrm{[-]}$
$K_{Pu-4.2} \mathrm{[-]}$
$K_{Pu-4.5} \mathrm{[-]}$
$K_{Pu-5} \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Coefficient of under-pressure for $ \cfrac{h_l}{D}=3.6\ \text{to}\ 5 $

Valve position
Coefficient of under-pressure
Under-pressure behind the valve
Loss of pressure on the valve
Pressure on the valve
Cavitation number
$S/D$ $K_{Pu}$ $P_{u}$ $H_L$ $H_v$ $σ$
$\mathrm{ }$ $\mathrm{ }$ $\mathrm{m}$ $\mathrm{m}$ $\mathrm{m}$ $\mathrm{ }$
No data

$K_{Pu} \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Coefficient of under-pressure

$\text{if }\ \cfrac{h_l\cdot 10^3}{D}\le 0$
$$K_{Pu}=K_{Pu-0}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 2$
$$K_{Pu}=K_{Pu-2}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 2.5$
$$K_{Pu}=K_{Pu-2.5}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 3$
$$K_{Pu}=K_{Pu-3}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 3.5$
$$K_{Pu}=K_{Pu-3.5}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 3.6$
$$K_{Pu}=K_{Pu-3.6}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 3.9$
$$K_{Pu}=K_{Pu-3.9}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 4$
$$K_{Pu}=K_{Pu-4}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 4.2$
$$K_{Pu}=K_{Pu-4.2}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 4.5$
$$K_{Pu}=K_{Pu-4.5}$$
$\text{else}$
$$K_{Pu}=K_{Pu-5}$$

$P_{u} \mathrm{[m]}$
No data
$S/D\mathrm{[-]}$
Under-pressure behind the valve

$$P_{u}=\max\left(K_{Pu}\cdot H_v, -\cfrac{p_{air}}{ρ\cdot g}\right)$$

$H_L \mathrm{[m]}$
$H_v \mathrm{[m]}$
No data
$S/D\mathrm{[-]}$
Loss of height on valve and pressure height on Howell-Bunger valve

$$H_L=\cfrac{v^2}{2\cdot g}\cdot ζ$$
$$H_v=H-P_{u}+\cfrac{v^2}{2\cdot g}-\cfrac{v^2}{2\cdot g}\cdot Σζ+\left(1-Q_p\right)\cdot ΔP$$

$σ \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Cavitation number

$$σ=\cfrac{\cfrac{p_{air}-P_{SV}}{ρ\cdot g}+H-H_L}{H_v}$$
Valve position
Coefficient of lenght $ L_1 $ for $ \cfrac{T_x}{D}=10 $
Coefficient of lenght $ L_1 $ for $ \cfrac{T_x}{D}=20 $
Coefficient of lenght $ L_1 $ for $ \cfrac{T_x}{D}=30 $
Coefficient of lenght $ L_1 $ for $ \cfrac{T_x}{D}=40 $
Lenght $ L_1 $
$S/D$ $L_{1-10}$ $L_{1-20}$ $L_{1-30}$ $L_{1-40}$ $L_1$
$\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{m}$
No data

$L_{1-10} \mathrm{[-]}$
$L_{1-20} \mathrm{[-]}$
$L_{1-30} \mathrm{[-]}$
$L_{1-40} \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Coefficient of lenght $ L_1 $

$L_1 \mathrm{[m]}$
No data
$S/D\mathrm{[-]}$
Lenght $ L_1 $

$\text{if }\ \cfrac{T_x\cdot 10^3}{D}< 10$
$$L_1=L_{1-10}\cdot\cfrac{D}{1000}$$
$\text{else if }\ \cfrac{T_x\cdot 10^3}{D}< 20$
$$L_1=L_{1-20}\cdot\cfrac{D}{1000}$$
$\text{else if }\ \cfrac{T_x\cdot 10^3}{D}< 30$
$$L_1=L_{1-30}\cdot\cfrac{D}{1000}$$
$\text{else}$
$$L_1=L_{1-40}\cdot\cfrac{D}{1000}$$
Valve position
Coefficient of lenght $ L_2 $ for $ \cfrac{T_x}{D}=10 $
Coefficient of lenght $ L_2 $ for $ \cfrac{T_x}{D}=20 $
Coefficient of lenght $ L_2 $ for $ \cfrac{T_x}{D}=30 $
Coefficient of lenght $ L_2 $ for $ \cfrac{T_x}{D}=40 $
Coefficient of lenght $ L_2 $ for $ \cfrac{T_x}{D}=50 $
Lenght $ L_2 $
$S/D$ $L_{2-10}$ $L_{2-20}$ $L_{2-30}$ $L_{2-40}$ $L_{2-50}$ $L_2$
$\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{m}$
No data

$L_{2-10} \mathrm{[-]}$
$L_{2-20} \mathrm{[-]}$
$L_{2-30} \mathrm{[-]}$
$L_{2-40} \mathrm{[-]}$
$L_{2-50} \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Coefficient of lenght $ L_2 $

$L_2 \mathrm{[m]}$
No data
$S/D\mathrm{[-]}$
Lenght $ L_2 $

$\text{if }\ \cfrac{T_x\cdot 10^3}{D}< 10$
$$L_2=L_{2-10}\cdot\cfrac{D}{1000}$$
$\text{else if }\ \cfrac{T_x\cdot 10^3}{D}< 20$
$$L_2=L_{2-20}\cdot\cfrac{D}{1000}$$
$\text{else if }\ \cfrac{T_x\cdot 10^3}{D}< 30$
$$L_2=L_{2-30}\cdot\cfrac{D}{1000}$$
$\text{else if }\ \cfrac{T_x\cdot 10^3}{D}< 40$
$$L_2=L_{2-40}\cdot\cfrac{D}{1000}$$
$\text{else}$
$$L_2=L_{2-50}\cdot\cfrac{D}{1000}$$
Valve position
Under-pressure coefficient in hole 1 for $ \cfrac{h_l}{D}=0 $
Under-pressure coefficient in hole 1 for $ \cfrac{h_l}{D}=2 $
Under-pressure coefficient in hole 1 for $ \cfrac{h_l}{D}=2.5 $
Under-pressure coefficient in hole 1 for $ \cfrac{h_l}{D}=3 $
Under-pressure coefficient in hole 1 for $ \cfrac{h_l}{D}=3.5 $
$S/D$ $K_{Pu-air1-0}$ $K_{Pu-air1-2}$ $K_{Pu-air1-2.5}$ $K_{Pu-air1-3}$ $K_{Pu-air1-3.5}$
$\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$
No data

$K_{Pu-air1-0} \mathrm{[-]}$
$K_{Pu-air1-2} \mathrm{[-]}$
$K_{Pu-air1-2.5} \mathrm{[-]}$
$K_{Pu-air1-3} \mathrm{[-]}$
$K_{Pu-air1-3.5} \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Under-pressure coefficient in hole 1 for $ \cfrac{h_l}{D}=0\ \text{to}\ 3.5 $

Valve position
Under-pressure coefficient in hole 1 for $ \cfrac{h_l}{D}=3.6 $
Under-pressure coefficient in hole 1 for $ \cfrac{h_l}{D}=3.9 $
Under-pressure coefficient in hole 1 for $ \cfrac{h_l}{D}=4 $
Under-pressure coefficient in hole 1 for $ \cfrac{h_l}{D}=4.2 $
Under-pressure coefficient in hole 1 for $ \cfrac{h_l}{D}=4.5 $
Under-pressure coefficient in hole 1 for $ \cfrac{h_l}{D}=5 $
$S/D$ $K_{Pu-air1-3.6}$ $K_{Pu-air1-3.9}$ $K_{Pu-air1-4}$ $K_{Pu-air1-4.2}$ $K_{Pu-air1-4.5}$ $K_{Pu-air1-5}$
$\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$
No data

$K_{Pu-air1-3.6} \mathrm{[-]}$
$K_{Pu-air1-3.9} \mathrm{[-]}$
$K_{Pu-air1-4} \mathrm{[-]}$
$K_{Pu-air1-4.2} \mathrm{[-]}$
$K_{Pu-air1-4.5} \mathrm{[-]}$
$K_{Pu-air1-5} \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Under-pressure coefficient in hole 1 for $ \cfrac{h_l}{D}=3.6\ \text{to}\ 5 $

Valve position
Under-pressure coefficient in hole 2 for $ \cfrac{h_l}{D}=0 $
Under-pressure coefficient in hole 2 for $ \cfrac{h_l}{D}=2 $
Under-pressure coefficient in hole 2 for $ \cfrac{h_l}{D}=2.5 $
Under-pressure coefficient in hole 2 for $ \cfrac{h_l}{D}=3 $
Under-pressure coefficient in hole 2 for $ \cfrac{h_l}{D}=3.5 $
$S/D$ $K_{Pu-air2-0}$ $K_{Pu-air2-2}$ $K_{Pu-air2-2.5}$ $K_{Pu-air2-3}$ $K_{Pu-air2-3.5}$
$\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$
No data

$K_{Pu-air2-0} \mathrm{[-]}$
$K_{Pu-air2-2} \mathrm{[-]}$
$K_{Pu-air2-2.5} \mathrm{[-]}$
$K_{Pu-air2-3} \mathrm{[-]}$
$K_{Pu-air2-3.5} \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Under-pressure coefficient in hole 2 for $ \cfrac{h_l}{D}=0\ \text{to}\ 3.5 $

Valve position
Under-pressure coefficient in hole 2 for $ \cfrac{h_l}{D}=3.6 $
Under-pressure coefficient in hole 2 for $ \cfrac{h_l}{D}=3.9 $
Under-pressure coefficient in hole 2 for $ \cfrac{h_l}{D}=4 $
Under-pressure coefficient in hole 2 for $ \cfrac{h_l}{D}=4.2 $
Under-pressure coefficient in hole 2 for $ \cfrac{h_l}{D}=4.5 $
Under-pressure coefficient in hole 2 for $ \cfrac{h_l}{D}=5 $
$S/D$ $K_{Pu-air2-3.6}$ $K_{Pu-air2-3.9}$ $K_{Pu-air2-4}$ $K_{Pu-air2-4.2}$ $K_{Pu-air2-4.5}$ $K_{Pu-air2-5}$
$\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{ }$
No data

$K_{Pu-air2-3.6} \mathrm{[-]}$
$K_{Pu-air2-3.9} \mathrm{[-]}$
$K_{Pu-air2-4} \mathrm{[-]}$
$K_{Pu-air2-4.2} \mathrm{[-]}$
$K_{Pu-air2-4.5} \mathrm{[-]}$
$K_{Pu-air2-5} \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Under-pressure coefficient in hole 2 for $ \cfrac{h_l}{D}=3.6\ \text{to}\ 5 $

Valve position
The force at the valve axis x
Under-pressure coefficient in hole 1
Under-pressure coefficient in hole 2
Under-pressure in hole 1
Under-pressure in hole 2
$S/D$ $F_{bx}$ $K_{Pu-air1}$ $K_{Pu-air2}$ $P_{u-air1}$ $P_{u-air2}$
$\mathrm{ }$ $\mathrm{kN}$ $\mathrm{ }$ $\mathrm{ }$ $\mathrm{m}$ $\mathrm{m}$
No data

$F_{bx} \mathrm{[kN]}$
No data
$S/D\mathrm{[-]}$
The force at the valve axis x

$$F_{bx}=\cfrac{π\cdot D^2}{4\cdot 10^9}\cdot ρ\cdot g\cdot H_v\cdot K_{bx}$$

$K_{Pu-air1} \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Under-pressure coefficient in hole 1

$\text{if }\ \cfrac{h_l\cdot 10^3}{D}\le 0$
$$K_{Pu-air1}=K_{Pu-air1-0}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 2$
$$K_{Pu-air1}=K_{Pu-air1-2}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 2.5$
$$K_{Pu-air1}=K_{Pu-air1-2.5}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 3$
$$K_{Pu-air1}=K_{Pu-air1-3}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 3.5$
$$K_{Pu-air1}=K_{Pu-air1-3.5}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 3.6$
$$K_{Pu-air1}=K_{Pu-air1-3.6}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 3.9$
$$K_{Pu-air1}=K_{Pu-air1-3.9}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 4$
$$K_{Pu-air1}=K_{Pu-air1-4}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 4.2$
$$K_{Pu-air1}=K_{Pu-air1-4.2}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 4.5$
$$K_{Pu-air1}=K_{Pu-air1-4.5}$$
$\text{else}$
$$K_{Pu-air1}=K_{Pu-air1-5}$$

$K_{Pu-air2} \mathrm{[-]}$
No data
$S/D\mathrm{[-]}$
Under-pressure coefficient in hole 2

$\text{if }\ \cfrac{h_l\cdot 10^3}{D}\le 0$
$$K_{Pu-air2}=K_{Pu-air2-0}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 2$
$$K_{Pu-air2}=K_{Pu-air2-2}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 2.5$
$$K_{Pu-air2}=K_{Pu-air2-2.5}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 3$
$$K_{Pu-air2}=K_{Pu-air2-3}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 3.5$
$$K_{Pu-air2}=K_{Pu-air2-3.5}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 3.6$
$$K_{Pu-air2}=K_{Pu-air2-3.6}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 3.9$
$$K_{Pu-air2}=K_{Pu-air2-3.9}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 4$
$$K_{Pu-air2}=K_{Pu-air2-4}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 4.2$
$$K_{Pu-air2}=K_{Pu-air2-4.2}$$
$\text{else if }\ \cfrac{h_l\cdot 10^3}{D}\le 4.5$
$$K_{Pu-air2}=K_{Pu-air2-4.5}$$
$\text{else}$
$$K_{Pu-air2}=K_{Pu-air2-5}$$

$P_{u-air1} \mathrm{[m]}$
No data
$S/D\mathrm{[-]}$
Under-pressure in hole 1

$$P_{u-air1}=\max\left(K_{Pu-air1}\cdot H_v, -\cfrac{p_{air}}{ρ\cdot g}\right)$$

$P_{u-air2} \mathrm{[m]}$
No data
$S/D\mathrm{[-]}$
Under-pressure in hole 2

$$P_{u-air2}=\max\left(K_{Pu-air2}\cdot H_v, -\cfrac{p_{air}}{ρ\cdot g}\right)$$
Valve position
Air flow
Air velocity in hole 1
Air velocity in hole 2
The flow area of the aerated hole
$S/D$ $Q_{air}$ $v_{air1}$ $v_{air2}$ $A_{air}$
$\mathrm{ }$ $\mathrm{m^3/s}$ $\mathrm{m/s}$ $\mathrm{m/s}$ $\mathrm{m^2}$
No data

$Q_{air} \mathrm{[m^3/s]}$
No data
$S/D\mathrm{[-]}$
Air flow

$\text{if }\ \text{n}= \text{no}$
$$Q_{air}=NAN$$
$\text{else}$
$$Q_{air}=0.04\cdot Q$$

$v_{air1} \mathrm{[m/s]}$
$v_{air2} \mathrm{[m/s]}$
No data
$S/D\mathrm{[-]}$
Air velocity

$\text{if }\ \text{n}= \text{no}$
$$v_{air1}=NAN$$
$\text{else}$
$$v_{air1}=\min\left(0.7\cdot\sqrt{-\cfrac{2\cdot P_{u-air1}\cdot g\cdot ρ}{ρ_{air}}}, 250\right)$$
$\text{if }\ \text{n}= \text{no}$
$$v_{air2}=NAN$$
$\text{else}$
$$v_{air2}=\min\left(0.7\cdot\sqrt{-\cfrac{2\cdot P_{u-air2}\cdot g\cdot ρ}{ρ_{air}}}, 250\right)$$

$A_{air} \mathrm{[m^2]}$
No data
$S/D\mathrm{[-]}$
The flow area of the aerated hole

$\text{if }\ \text{n}= \text{no}$
$$A_{air}=NAN$$
$\text{else}$
$$A_{air}=\cfrac{Q_{air}}{v_{air1}+v_{air2}}$$
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