What is CFD? — Lesson 1

Summary

This video introduces Ansys Fluent and provides a comprehensive overview of Computational Fluid Dynamics (CFD). It explains the basic principles of CFD, including how it predicts fluid flow, heat transfer, and chemical reactions by solving key physical equations like conservation of mass, energy, and momentum. The video highlights the versatility of CFD in applications like design optimization and troubleshooting while emphasizing its role in complementing experimental testing. Finally, it explains how Ansys CFD solvers use the finite volume method to discretize the problem and solve complex algebraic equations, delivering valuable insights into fluid dynamics and related phenomena.

Takeaways

• 😀 CFD is a method to predict fluid flow, heat and mass transfer, chemical reactions, and other related phenomena.
• 😀 CFD solves equations based on Newton's second law, conservation of mass, energy, and quantities transported by the flow.
• 😀 CFD provides detailed information on flow fields, including pressure, velocity, temperature, and other quantities.
• 😀 With CFD, you can determine forces like drag and lift from the flow field.
• 😀 CFD can analyze multiphase flows (gas-liquid, gas-solid) and phase distribution.
• 😀 CFD helps in studying chemical reactions, combustion, and pollutant formation in different species or phases.
• 😀 CFD complements testing by reducing the number of experiments required, saving time and costs.
• 😀 The Ansys CFD solvers use the finite volume method to discretize the study domain into control volumes.
• 😀 Equations like conservation of mass, momentum, and energy are solved for each control volume in CFD.
• 😀 After discretization, the equations become algebraic, and numerical methods are used to solve them.
• 😀 The solution process in CFD involves solving non-linear equations to obtain the desired results.

Q & A

What is CFD?

CFD stands for Computational Fluid Dynamics, a method used to predict fluid flow, heat and mass transfer, chemical reactions, and other related phenomena by solving equations that represent Newton's second law, conservation of mass, energy, and other transported quantities.

What are the key equations used in CFD?

The key equations used in CFD are the continuity equation, momentum equations (derived from Newton's second law), and potentially the energy and species conservation equations, depending on the nature of the problem being solved.

How does CFD help engineers?

CFD helps engineers by providing detailed information about the flow field, including pressure, velocity, temperature, and other quantities, which can be used to determine forces like drag and lift. It also helps in understanding multiphase flows, chemical reactions, combustion, and pollutant formation.

What role does CFD play in product development?

CFD plays a crucial role in product development by aiding in conceptual studies, detailed design, optimization, troubleshooting, and redesigning processes. It allows engineers to understand system performance early in the design phase.

How does CFD complement testing and experimentation?

CFD complements testing by reducing the effort and cost required for experiments. While it does not eliminate the need for physical testing, it reduces the number of tests and can provide a wealth of detailed information about device performance that might be difficult to obtain experimentally.

What is the finite volume method used in Ansys CFD solvers?

The finite volume method involves discretizing the system of interest, called the domain, into a finite set of control volumes (mesh cells). Equations for mass, momentum, energy, and species are solved for each control volume, and the solution for each cell depends on its neighboring cells.

What is meant by discretizing the domain in CFD?

Discretizing the domain means dividing the continuous system into smaller, finite control volumes (mesh cells). Each control volume is used to solve the governing equations (e.g., conservation of mass, momentum, energy) to find the flow properties at each point in the domain.

What are the types of terms found in the general form of the CFD equations?

The general form of CFD equations includes terms for unsteady behavior, convection, diffusion, and source terms. Source terms may include body forces in momentum equations or heat released by chemical reactions in energy equations.

What happens to the CFD equations after discretization?

After discretization, the partial differential equations become a system of algebraic equations. The solution for each control volume depends on its neighbors, and numerical methods are used to solve the system of equations.

Why is CFD considered valuable in simulating multiphase flows or chemical reactions?

CFD is valuable in simulating multiphase flows or chemical reactions because it can model complex interactions between different phases (e.g., gas-liquid or gas-solid) and provide insights into phase distribution, chemical reactions, combustion, and pollutant formation that are challenging to obtain experimentally.