Multiphase flow analysis involves analyzing and understanding the behaviors of fluid flows in complex systems, also known as multiphase flow systems, and predicting their performance under different conditions to design and optimize them.

Single-phase flow systems transfer only one kind of fluid and experience a few ranges of problems and require flow analysis to solve them. However, multiphase flow systems experience far more problems due to containing several phases of fluids and the complexity of systems originating from the interaction and behavior of multiple phases of fluids.

Hence, it requires a more detailed analysis to solve their problems, also known as Multiphase Flow Analysis.

This article will give us a brief overview of multiphase flow analysis. But first, let’s understand the topic of multiphase flow systems and the problems they experience in detail.

What Are Multiphase Flow Systems?

As the name suggests, multiphase flow systems transfer two or more phases of matter or fluids, such as liquid-gas, liquid-liquid, and gas-gas.

These systems are used in many industries, such as oil and gas pipelines, chemical processing, food processing, etc., because of their efficient and cost-effective transportation of fluids.

Multiphase flow systems allow industries to eliminate dependency on installing many separate single-phase flow systems.

However, the more efficient the systems are, the more challenging it is to design, operate and maintain them. Due to the complex interaction between different phases of fluids, multiphase flow systems often experience numerous problems, such as blockages, phase separation, flow instabilities, corrosion, etc. 

That’s why it is crucial to perform multiphase flow analysis for complex systems to design and optimize them to work efficiently and safely.

Multiphase Flow Analysis: An Overview

The multiphase flow analysis is crucial for complex flow systems to understand the behavior of fluids under different conditions to predict systems performance.

It can be performed using various experimental and computational methods to study fluid behavior in complex systems.

• Experimental Technique

In the experimental technique, the visualization methods like high-speed photography, and measurement techniques, such as flow meters and sensors, are employed to analyze fluid behaviors.

But this technique is limited in scope, time-consuming, and expensive.

• Computational Fluid Dynamics

On the other hand, the computational method or Computational Fluid Dynamics ( CFD) is an advanced approach.

It simulates the behavior of fluid under different conditions in a computer program. This method uses fluid mechanics numerical to solve the equation that influences the flow of fluid, such as the conservation equation of mass, momentum, and energy.

The computational technique is fast, accurate, economical, and can analyze far more complex systems than the experimental technique.

Important approaches to Multiphase Flow Analysis

Here are a couple of other important methods that are used in multiphase flow analysis:

1. Eulerian-Eulerian (EE)  approach

One of the most used techniques for multi-flow simulation is

The Eulerian-Eulerian (EE)  approach.  It is a numerical method used to simulate multiphase analysis, which treats each separate phase as continuous fluid with its own velocity and properties.

The biggest advantage of the Eulerian-Eulerian approach is its ability to capture a big range of multiphase flow phenomena such as phase separation, phase change, interphase mass transfer, etc.
However, it can be costly as it requires a significant amount of computational resources to run multiphase flow simulations for complex systems.

2. Eulerian-Lagrangian Method

Another prominent approach for Multiphase system analysis is Eulerian-Lagrangian which also uses numerical methods for simulating multiphase flow systems.

In this approach, one face is simulated as a continuum, and the other phase is simulated using lagrangian particles.

This approach suits dispersed multiphase flow systems, such as gas-liquid flows with bubbles, liquid-liquid flow with droplets, and solid and liquid flow with particles. It is computationally more efficient than the Eulerian-Eulerian approach.

However, sometimes, it is unable to capture specific fluid behavior, such as phase separation and interphase mass transfer.

How Does CFD simulation Assist in Multiphase Flow Analysis: 4 Steps

Now let’s look at the brief process of multiphase flow analysis using CFD simulation.

1. Define the Problems

The first step of multiphase flow analysis using CFD is to define the problems and objective of the simulation.

the definition should assess the system’s geometry for which simulation must be carried out, specifying boundary conditions and selecting suitable numerical methods, such as the Eulerian-Eulerian and Eulerian-Lagrangian approaches.

This step should involve evaluating the shape and size of systems, locations of components such as inlets and outlets, and any other component that can impact the flow of fluids.

Specifying boundary conditions should include inlet and outlet velocities, temperature, and other fluid properties.

2. Create a Geometry Model

After defining the problem, the next step should be creating a geometry model of a multiphase flow system.

This involves creating a three-dimensional model of the complex system, including dimensions of components such as pipes, valves, and pumps, as well as external factors such as the surrounding environment and structure that may have any influence on the flow of fluid.

3. Generate Mesh

In this step, the mesh is ready to be generated, a  grid of small elements representing the complex system.

This step should be performed carefully as it is imperative for accurate system simulation.

4. Select Solver

There are numerous numerical methods available for solving the equation of complex systems, such as the finite volume method (FVM), boundary element method (BEM), and finite element method ( FEM).
Depending on the problem being analyzed, a solver should be selected, and the simulation should be completed.
These are the typical steps of multiphase flow analysis, and they may vary depending on the requirement of the analysis.

Conclusion

Multiphase flow analysis can help you effectively understand complex systems, predict fluid flow behavior under different conditions, and optimize complex systems for safe and efficient operations.

However, due to its complexity, multiphase flow analysis requires good experience and the expertise of engineers to get accurate results to optimize systems.
We at Mechartes provide all kinds of FEA and CFD simulation services for core industries, including multiphase flow analysis of complex systems.