This document is my compiled notes for MEC 511: Thermodynamics and Fluids at TMU. All information comes from my professor's lectures and the textbook A Brief Introduction to Fluid Mechanics by Young et al., and Fundamentals of Engineering Thermodynamics by Moran et al..
Adam Szava - 2tor.ca
S2022
Fluid Mechanics is the discipline within applied mechanics that is concerned with the behavior of liquids and gases at rest or in motion. The different flow conditions for fluids are highly dependent on numerous parameters which describe them like the physical size $\ell$ (like the diameter of a pipe), the speed $V$(like the windspeed) and the pressure $p$.
Fluid mechanics can be separated into two subjects:
<aside> ➕ Definition 1.1.1 (Sheering Stress)
A sheering stress is a force per unit area caused by a tangential force acting on a surface. We can define it as (where $A$ is the surface area of the plate in contact with the fluid):
$$ \text{Shear stress} = \frac{\vec{F}_{\text{shear}}}{A} $$
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Figure 1.1.1: Sheering stress.
<aside> ➕ Definition 1.1.2 (Fluid)
A fluid is a substance that has no fixed shape, and yields easily to external pressure, usually a gas or a liquid. More formally, a fluid is defined as a substance that deforms continuously when acted on by sheering stress of any magnitude.
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Figure 1.1.2: Comparing solids and fluids.
In a solid, the sheer force will only deform the object so far before the rigidity of the solid stops it from deforming further. In a fluid, the substance will continuously deform (flow).
In this course, we assume that all fluid characteristics vary continuously throughout the fluid, that is we treat the fluid as a continuum. This means that, while the fluid is made up of individual discrete molecules, we treat their size to be negligible when compared to the container.
The only thing of note in this section is the MLT and FLT systems of measurement. Essentially all units can be expressed as some combination of either mass, length, and time (MLT) of force, length, and time (FLT), and it is your decision which one is more suitable. The following table summarizes common physical quantities:
Additionally, you can convert between MLT and FLT by: