AUSTRALIA SINGAPORE
WHAT is multiphase cfd simulation?
Multiphase Computational Fluid Dynamics (CFD) simulation is a computational technique used to model and analyse fluid flows involving multiple phases. In the real world, many fluid flow problems consist of two or more distinct phases coexisting and interacting with each other. Each phase can have its own physical properties, velocity and volume fraction within the mixture. Multiphase CFD simulation allows engineers and scientists to study these complex flows and understand the behaviour of each phase and their interactions. The phases involved in multiphase CFD simulations can be different states of matter, such as:
Gas-Liquid: In scenarios like bubbly flows, where gas bubbles are dispersed in a liquid medium or in spray and atomisation processes where liquid droplets are dispersed in a gas.
Liquid-Liquid: Seen in cases like emulsions and oil-water flows, where two immiscible liquids interact.
Gas-Solid: Common in fluidised beds, where solid particles are suspended and carried by a gas stream, or in pneumatic conveying, where particles are transported in a gas flow.
Liquid-Solid: As in sedimentation processes or slurries, where solid particles settle in a liquid medium.
Gas-Solid-Liquid: Common in simulation of a chemical reactor which may consist of freeboard, liquid and solid particles.
Simulating multiphase flows is challenging due to the complex interactions between phases, such as momentum exchange, heat and mass transfer and phase change (e.g., evaporation or condensation). These interactions often lead to phenomena like interface deformation, phase segregation and formation of patterns, all of which significantly influence the behaviour of the system. Several numerical techniques are used for multiphase CFD simulation, including:
Eulerian-Eulerian Approach: The most common method, where separate sets of Navier-Stokes equations are solved for each phase and interphase interactions are modelled through additional source terms in the momentum and continuity equations.
Volume of Fluid (VOF) Method: This method tracks the interface between phases by assigning a volume fraction variable to each phase. The interface is explicitly captured as a sharp interface within the computational grid.
Lagrangian Discrete Phase Model (DPM): This method tracks individual particles or droplets in a Lagrangian frame and accounts for the interactions between particles and fluid phases. Suitable for dilute particle-laden flows, where particles are treated as discrete entities and tracked through the flow field.
By simulating these complex flows, engineers and researchers can optimise processes, design more efficient systems and gain insights into the physics of multiphase phenomena.
WHAT ARE THE MAJOR STEPS TO perform cfd simulations?
Computational Fluid Dynamics (CFD) is a method used to simulate and analyse fluid flow behaviour using numerical methods. The major steps involved in performing CFD simulation are:
Problem Definition: Fluid dynamics problem to be solved are clearly defined. This involves specifying the domain (the region in which fluid flow occurs), boundary conditions (inlet, outlet, walls, etc.), initial conditions (starting state of the fluid) and the governing equations that describe the fluid flow (e.g., Navier-Stokes equations for incompressible flow).
Pre-processing: This step involves preparing the geometric model of the domain to be simulated. It includes converting the physical geometry into a discrete computational mesh or grid. The mesh quality and resolution are crucial for accurate results. CFD solvers use various types of meshes, such as structured grids, unstructured grids, or hybrid grids.
Discretisation: The governing equations are transformed from continuous partial differential equations into discrete algebraic equations using numerical methods. The most common approach is to use finite difference, finite volume, or finite element methods to approximate the derivatives and integrate the equations over each cell or control volume of the mesh.
Numerical Solver: The numerical algorithms to solve the discretised equations are implemented. Depending on the problem type, various solvers like explicit, implicit, steady-state, or transient solvers may be used. Common techniques include the SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) algorithm for pressure-velocity coupling in incompressible flows.
Time Integration (if applicable): For transient flows or time-dependent problems, the equations need to be integrated in time. Time-stepping methods like the explicit or implicit Euler method, Runge-Kutta methods or multistep methods are used to advance the solution in time.
Boundary Conditions: Appropriate boundary conditions to the domain to replicate the physical behaviour of the fluid at the boundaries are assigned. These conditions include specifying inlet velocity, pressure, temperature and other relevant parameters. Boundary conditions play a crucial role in capturing the actual flow behaviour.
Iterative Solution: The solution of the discretised equations involves iterative processes. The solver iteratively refines the solution until it converges to a stable and accurate result. Convergence criteria are defined to determine when the solution has reached the desired accuracy.
Post-processing: Once the CFD simulation is completed, post-processing is performed to analyse and visualise the results. This step involves extracting relevant data, generating visualisations (contour plots, streamlines, vector plots, etc.), and interpreting the results to gain insights into the fluid flow behaviour.
Interpretation and Conclusion: Finally, interpret the CFD results in the context of the original problem and draw conclusions from the simulation data.
COMPUTATIONAL FLUID DYNAMICS
Our CFD analysis services focus on multiphase, multiphysics, multispecies, chemical processes, sliding mesh, combustion and energy production processes. We exclusively use ANSYS Fluent, the most powerful CFD simulation solver available, enabling our clients to optimise their system's performance with greater speed and efficiency. Fluent's well-validated physical modelling capabilities deliver fast, accurate results across a wide range of applications. Our CFD simulation services include, but are not limited to, the following:
- Chemical Plant: unit operations, gas dispersion analysis and vapour cloud explosions
- Chemical Reaction: reactor design, scale-up, mixing, mass transfer, catalyst and reaction kinetics
- Food & Beverage: equipment design, preparation processes, storage and distribution
- Heat Transfer: temperature distribution, conjugate heat transfer, heat losses or gains
- Mining & Mineral Processing: equipment design, large particles and multiphase simulation
- Renewable Energy: hydrogen production, storage and distribution
- Ship Building: design of ship hull, assess propulsion system, gas abatement and ballast water
- Water and wastewater: unit operations, sump pump, stormwater and pressure surge analysis
Process Dynamics Simulation
Our process modelling consultants deliver dynamic simulation services to clients across various industries. Below are several application examples.
- Chemical processing: designs, optimises or troubleshoot chemical process plants
- Green hydrogen production: optimises electrolysis processes to reduce production costs
- Automotive industry: optimises internal combustion of hydrogen car
- Aerospace industry: enhances performance and reliability of fuel systems
- Power generation: improves boilers, turbines and control systems to boost efficiency and stability
- Pharmaceutical industry: ensures effective and efficient scale-up from pilot to production
- Water treatment: efficiently removes contaminants to ensure a reliable clean water supply
- Environmental engineering: optimises waste-water treatment
SIMULATION CONSULTANTS
Our simulation consultants provide expert simulation services to clients across various industries. Currently, we offer simulation analysis to clients in Australia and Singapore, including: (1) Computational Fluid Dynamics, (2) Fluid Structure Interaction, (3) Impact Transient Analysis and (4) Process Dynamics Simulation.
Conducting simulations without proper expertise can lead to misleading results. To ensure accuracy, we only assign personnel with PhD qualifications in modelling and simulation. Their advanced academic training equips them with the ability to tackle complex problems and develop innovative solutions tailored to the specific needs of our clients. Our team of simulation specialists is supported by conventional engineering practices, ensuring that the solutions provided are not only theoretically sound but also practically viable. This integration of advanced simulation techniques with real-world engineering principles ensures that our clients receive solutions that are both accurate and implementable. We utilise ANSYS simulation software, which embodies over 1,000 person-years of R&D and employs rigorously validated models, assuring stakeholders of highly accurate results. Our simulation consultants boast a combined experience of over 50 years in modelling and simulation, ensuring the highest standards of service and reliability.
WHAT is multiphysics cfd simulation?
Multiphysics Computational Fluid Dynamics (CFD) simulation is a computational technique that combines multiple physical phenomena or governing equations to analyse and predict the behaviour of complex systems involving fluid flow and other coupled physical processes. CFD itself is a branch of fluid mechanics that uses numerical methods and algorithms to solve the Navier-Stokes equations and simulate fluid flow.
In many real-world engineering and scientific problems, fluid flow is just one aspect of a larger, interconnected system where other physical processes also play a significant role. Some examples of these coupled phenomena include:
Heat Transfer: The transfer of thermal energy through conduction, convection, and radiation. It becomes essential to consider heat transfer when analysing fluid flow in situations where temperature gradients significantly impact the system.
Mass Transport: The movement of various species or substances within the fluid. It is crucial in scenarios like reacting flows, combustion processes and diffusion-driven phenomena.
Structural Mechanics: Involves studying the deformation and stress distribution in solid structures due to fluid flow or other external forces.
Electromagnetics: In cases where electromagnetic fields interact with fluid flow, such as magnetohydrodynamics (MHD) problems.
Acoustics: Analysing sound generation and propagation in fluids, which is essential for studying aerodynamics and underwater acoustics.
Multiphysics CFD simulation brings together the mathematical models representing these different physical processes and solves them simultaneously or in a coupled manner. The complexity of such simulations requires powerful numerical algorithms, substantial computational resources and specialised software that can handle the intricacies of each phenomenon.
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Impact Transient ANALYSIS
We offer impact transient analysis services to characterise the physics of short-duration events for products that undergo highly nonlinear, transient dynamic forces. Our analysis gains insight into how a structure responds when subjected to severe loadings from another solid object.
Short-duration severe loading analysis to study the interaction between various solid bodies
Low velocity object crashing into a structure such as:
- Hostile vehicle mitigation such as a truck crashing into gate barriers or bollards
- Crash test of a large ships
High velocity object penetrating a structure such as:
- Penetration mechanics of ballistic impacting into a composite material
- Material resilience study from blast fragment breaches
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FLUID STRUCTURE INTERACTION
The flow of fluids through pipe connections, over aerofoils, turbine blades and other structures can generate unsteady forces on the surrounding parts that cause them to move. This movement may be intentional and necessary or unintentional but unavoidable. Our simulation consultants which consist of FEA and CFD consultants are experience in coupling various modelling & simulation tools allow us to perform fluid structure interaction (FSI) analysis which can assist the clients to understand and solve product design challenges. Our FSI & simulation services include but not limited to:
Fluid Structure Coupling
- CFD based applications
- Mechanical based applications
Thermal Structure Coupling
- Engines, gas turbines, heat exchangers
- Cryogenic components and systems
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