## Chapter 1Introduction

“If we get through for two minutes only, it will be a start.”

The Jam, Start! (1980).

Fluid dynamics is concerned with the motion of ﬂuids (liquids and gases) and the forces on them. “Computational” refers to computation of the ﬂow and forces using numerical analysis. A literal deﬁnition of computational ﬂuid dynamics might therefore be the prediction of ﬂuid motion and forces by computation using numerical analysis.

Today, the term computational ﬂuid dynamics, usually abbreviated to CFD, is used to describe a broader range of calculations for a wide variety of scientiﬁc and engineering applications. In particular, it is commonly used for applications involving heat, including the following:

• engines, e.g. internal combustion engines, turbines;
• heat recovery, e.g. heat exchangers;
• thermal management, e.g. cooling, exhaust systems;
• thermal comfort, with heating, ventilation, and air conditioning.

Thermodynamics is an important consideration in many of these applications. It relates internal energy to temperature, which aﬀects the ﬂow of heat. Further sources of heat include thermal radiation and chemical reactions, in particular combustion. Heat transfer may involve conduction in solid materials, coupled with the ﬂuid ﬂow, known as conjugate heat transfer.

If we include the examples mentioned above, a modern deﬁnition of computational ﬂuid dynamics would be the prediction of ﬂuid motion and forces by computation using numerical analysis, generally extended to include heat, thermodynamics, chemistry and solids.

Numerical analysis provides many methods and algorithms that are suitable for CFD. The methods include ﬁnite volume, ﬁnite element and ﬁnite diﬀerence, which calculate the distributions of properties, e.g. pressure, velocity and temperature, over regions of space which are usually ﬁxed. Alternative methods attribute properties to particles represented by points in space, whose motions are calculated.

Particle methods are often used to approximate small scale ﬂow features such as liquid sprays, e.g. for cooling, coating, cleaning, agriculture, food production, ﬁre suppression, emission reduction and fuel injection. Solid particles can also be simulated in applications such as ﬁltration, erosion, and ﬂuidised beds.

As a presentation of general principles, this book describes numerical methodsto solve problems in ﬂuid dynamics, up to and including heat and some basic thermodynamics, without extending into thermal radiation, chemistry and solids.

The book is solely dedicated to the ﬁnite volume method, the chosen method for many decades in the most popular, general-purpose CFD codes, including OpenFOAM. It also does not describe particle methods.

Notes on CFD: General Principles - Chapter 1 Introduction