# Flow Analysis of a Butterfly valve

## Overview

The purpose of this numerical simulation is to validate the following performance parameters for incompressible flow through an industrial scale Butterfly Valve:

• Flow coefficient, CV
• Torque Coefficient, CT

The numerical simulation were carried out using the Reynolds-Averaged Navier–Stokes (RANS) approach with Turbulence modeling. The results of SimScale simulation runs were compared to the experimental results shown in [1]. The flow regime selected for the study has a Reynolds number in the order of Re=105.

Import validation project into workspace

## Geometry

The geometry of the study is a large scale discus shaped Butterfly valve (see Fig.1.). A brief description of the dimensions is provided by the table below.

Fig.1. Geometry of the Butterfly valve and pipe

Upstream Pipe Length Downstream Pipe Length Valve/Pipe Diameter Valve maximum thickness
Value [m] 8-12D 15D 1.8 m 0.36 m

## Domain and Analysis type

The domain is the internal region of the geometry with the domain extents same as the geometrical dimensions. Based on the flow physics and the geometry, a symmetry condition was applied to reduce the domain size and computational time. For the study a hexahedral mesh was created with the “Snappy Hex Mesh” on the SimScale platform (see Fig.2.). The Mesh was refined upstream, downstream and in the vicinity of the valve. Layer mesh was used on all wall regions for better accuracy. The details of the mesh are listed in the following table:

Mesh and Element types :

Mesh type Number of cells Type
Snappy-Hex-Mesh 2.9-3.5 million 3D hexahedral

Fig.2. Butterfly valve mesh used for the SimScale case

The numerical analysis performed is detailed as follows:

Tool Type : OPENFOAM®

Turbulence Model : K-Omega SST

## Simulation Setup

Fluid:

• Water: Kinematic viscosity [m²/s] (ν)=10−6

Boundary Conditions:

For the inlet boundary, a turbulent fixed velocity condition was applied, while a pressure boundary condition was applied at the outlet. No-slip condition was applied for the walls. The following table provides the further details.

Boundary type Velocity Pressure
Inlet Turbulent Fixed Value:  3 ms−1 Zero Gradient
Outlet Zero Gradient Fixed Value: 0 Pa
Wall no-slip Fixed Value: 0.0 ms−1 Zero Gradient
Symmetry Symmetry Symmetry

## Results

The numerical simulation results for the various valve opening angles are compared with experimental data provided shown by Xue guan Song [1]. The formulations for the Flow coefficient (CV) and Torque coefficient are taken as follows:

Flow coefficient:

$$C_{V}= \frac{Q}{\sqrt{\Delta P \times S_{g}}}$$

and Torque coefficient:

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

where, ΔP is the difference between upstream and downstream pressure in units of psi, Q is the flow rate in units of gpm, Sg is the specific gravity i.e = 1 for water, T(x) is the net torque about the x-axis and d is the diameter of the valve.

A comparison of the Flow coefficient obtained with SimScale and experimental results is given in Fig.3A and the figures Fig.3B shows the Torque coefficient comparison over the opening angle range of 20 to 85 degrees. For improved accuracy the pressure values were taken at 10D downstream and 8D upstream of the valve (upto approx 12D for higher angles).

Fig.3. Result comparison of numerical and experimental data. Flow Coefficient (left) and Torque Coefficient (right) with valve opening angles.

The Velocity contours at different valve opening angles are shown in the figure Fig.4 below.

Fig.4. Mean velocity contours on the symmetry plane for opening angle range of 30 to 70 degrees.

A visualization of the flow field by streamlines and the pressure distribution on the valve surface is shown by Fig.5.

Fig.5. Flow field visualisation by streamlines and pressure distribution on the valve for opening angle 50 degrees.

Please Note: To avoid large data, the import project only contains results for angles 20, 50 and 85 degrees

## References

 [1] Xue guan Song, Young Chul Park ; NUMERICAL ANALYSIS OF BUTTERFLY VALVE-PREDICTION OF FLOW COEFFICIENT AND HYDRODYNAMIC TORQUE COEFFICIENT, Proceedings of the World Congress on Engineering and Computer Science 2007 WCECS 2007, October 24-26, 2007, San Francisco, USA.

## Disclaimer

This offering is not approved or endorsed by OpenCFD Limited, producer and distributor of the OpenFOAM software and owner of the OPENFOAM® and OpenCFD® trade marks. OPENFOAM® is a registered trade mark of OpenCFD Limited, producer and distributor of the OpenFOAM software.