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Documentation

# Validation Case: Butterfly Valve with Subsonic solver

This validation case belongs to fluid dynamics and the aim of this case is to validate the following parameters inside a pipe with a butterfly valve:

• Pressure drop using the Subsonic solver in SimScale

The simulation results of SimScale were compared to the results presented in the study done by Song, Xue Guan, and Park, Young Chui with the title “Numerical Analysis of Butterfly Valve – Prediction of Flow Coefficient and Hydrodynamic Torque Coefficient“$$^1$$.

## Geometry

The model used in this validation case is a pipe with a discus shaped butterfly valve inside, which can be seen below: Figure 1: Pipe model with butterfly valve inside the opening at 20° angle

The dimensions of the pipe can be seen in the table below:

9 variants of valve opening angles ranging from 20° to 85° were used as a comparison to the reference study.

## Analysis Type and Mesh

Analysis Type: Steady-state, Subsonic with K-Epsilon turbulence model

Mesh and Element Types:

The mesh was created with SimScale’s Subsonic mesh type.

## Mesh Sensitivity

The Subsonic meshing algorithm with hexahedral cells was used to generate the mesh. For this simulation, refinement level 8 was chosen for the comparison of different valve openings. Figure 2: Mesh within the flow domain with fineness level 8 Figure 3: Subsonic meshing performed on the valve with refinement around the edge of the valve

## Simulation Setup

Fluid:

• Water
• Kinematic viscosity $$(\nu)$$: 9.338e-7 $$m^2/s$$
• Density $$(\rho)$$: 997.3 $$kg/m^3$$

Boundary Conditions: Figure 4: Boundary condition overview where the flow goes from left to right

The boundary conditions are the same for all opening angles and were assigned as shown in Table 3:

## Reference Solution

The reference solution for the flow coefficient and the torque coefficient is given in the following formulae:

Flow coefficient:

$$c_v = \frac{Q}{\sqrt{\Delta P \times S_g}} \tag{1}$$

where:

• $$c_v$$: flow coefficient
• $$Q$$: flow discharge $$(GPM-Gallons\,per\,minute)$$
• $$\Delta P$$: pressure drop $$(psi)$$
• $$S_g$$: specific gravity of water

Torque coefficient:

$$c_t = \frac{T(x)}{\Delta P \times d^3} \tag{2}$$

where:

• $$c_t$$: torque coefficient
• $$T(x)$$: torque in the x-axis $$(N.m)$$
• $$\Delta P$$: pressure drop $$(psi)$$
• $$d$$: diameter of pipe $$(in)$$

## Result Comparison

Comparison of the flow coefficient obtained from SimScale against the reference results obtained from  is given below: Figure 5: Flow coefficient comparison between reference results and SimScale

### Deviation to Reference

Deviation of the results gained from SimScale in comparison to the results obtained from  can be seen in Figure 6. The deviation gets very close to the reference results for the opening angle from 50-70 degrees. It has to be noted that small valve opening angles are deviating highly, which is expected according to Song, Xue Guan, and Park, Young Chui$$^1$$.

However, it must be noticed that at valve opening smaller than 20 degrees, the minimum error between CFX simulation and experimental data reach to 49.27958%.

Song, Xue Guan and Park, Young Chui Reference Figure 6: Deviation of SimScale results in comparison to the experimental data.

The flow contours inside the pipe when the valve is opened at the simulated opening angles as observed in our online post-processor: Figure 7: Velocity magnitude contours inside the pipe at the centerline when the valve is opened at a 20° – 35° angle. Figure 8: Velocity magnitude contours inside the pipe at the centerline when the valve is opened at a 50° – 80° angle.

Note

If you still encounter problems validating you simulation, then please post the issue on our forum or contact us.

Last updated: March 16th, 2022