Fluid Mechanics


by: Shashank_Aggarwal
Pressure, volume and temperature play an important part in the study of thermal fluids.
Thermal fluids is a branch of science and engineering divided into four sections:
Heat transfer
Thermodynamics
Fluid mechanics
Combustion



IFluid Mechanics

“Everything flows and nothing abides; everything gives way and nothing stays fixed.”
-Greek philosopher Heraclitus of Ephesus

We live in a world of fluids, i.e., substances that can flow. Unlike solids, fluids have no definite form but instead assume the shape of their containers. Fluids include all liquids and gases and a rather strange state of matter called plasma, an ionized gas that scientists believe accounts for 99% of the matter in the visible universe.

The importance and pervasiveness of fluids cannot be overstated. The Earth's atmosphere, oceans and core are fluids. We breathe and drink fluids. We sail ships in them and fly planes in them. We are entertained by images on our plasma televisions, illuminated by the glowing plasma in fluorescent lights, and awed by the amorphous streams of charged particles found in lightning.

Fluids are described by properties such as density, viscosity, and compressibility and are responsible for familiar phenomena that include pressure, buoyancy, and aerodynamic lift. The characteristics associated with fluids derive from the relatively weak interactions between their constituent particles. Atoms and molecules found in fluids are not bound to fixed positions

Some common materials known as non-Newtonian fluids don’t follow conventional laws of flow. With cornstarch and water, bread dough and peanut butter, resistance to flow changes with applied force. Silly Putty will ooze like a viscous liquid but, when pulled apart quickly, it will stiffen up and break cleanly in two. Other non-Newtonian fluids such as paint and mayonnaise flow more readily when disturbed.

The advances made in the understanding of fluids have been substantial, but we have much to learn. Understanding the transport of fluids across biological membranes, the airflow around the outer surfaces of airplanes and rockets, and the dynamics of our oceans, atmosphere, and convection in the Earth’s mantle provide ongoing challenges.

The study of fluids is one of the oldest branches of the physical sciences. Despite its long history, it continues to fascinate scientists and lay people alike. In this edition of CoolStuff we offer ways to engage your students in the study of fluids.

IIFundamentals of Fluid Mechanics
IIIReynolds Number
The Reynolds number is defined as the ratio of inertial forces to viscous forces and consequently quantifies the relative importance of these two types of forces for given flow conditions.Reynolds numbers frequently arise when performing scaling of fluid dynamics problems, and as such can be used to determine dynamic similitude between two different cases of fluid flow. They are also used to characterize different flow regimes within a similar fluid, such as laminar or turbulent flow: laminar flow occurs at low Reynolds numbers, where viscous forces are dominant, and is characterized by smooth, constant fluid motion; turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce chaotic vortices and eddies.
IVReynolds Number

Reynolds Number
VVenturimeter

A venturi can be used to measure the volumetric flow rate.

Since

\begin{align}
          Q &= v_1A_1 = v_2A_2\\
  p_1 - p_2 &= \frac{\rho}{2}(v_2^2 - v_1^2)
\end{align}

then


  Q =
   A_1\sqrt{\frac{2}{\rho} \cdot \frac{\left(p_1 - p_2\right)}{\left(\frac{A_1}{A_2}\right)^2 - 1}} =
   A_2\sqrt{\frac{2}{\rho} \cdot \frac{\left(p_1 - p_2\right)}{1 - \left(\frac{A_2}{A_1}\right)^2}}
VIVenturi meter

Venturimeter Discharge Calculation
VIIHydro static Forces
In a fluid at rest, all frictional stresses vanish and the state of stress of the system is called hydrostatic.Hydrostatics offers physical explanations for many phenomena of everyday life, such as why atmospheric pressure changes with altitude.
VIIIHydrostatic Forces

Hydrostatic Forces
IXProperties of Fluids

Fluid Mechanics is that branch of science which deals with the behavior of the fluids(liquids or gases) at rest as well as in motion.Properties of fluids are very well studied to deal with the static, kinematics and dynamic aspects of fluids.
XProperties of Fluids

Properties of Fluids
XISurface Tension
Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force.Surface tension has the dimension of force per unit length, or of energy per unit area. The two are equivalent—but when referring to energy per unit of area, people use the term surface energy—which is a more general term in the sense that it applies also to solids and not just liquids.
XIISurface Tension

Surface Tension
XIII Pascal Law: Pressure Measurement
Everyday pressure measurements, such as for tire pressure, are usually made relative to ambient air pressure. In other cases measurements are made relative to a vacuum or to some other specific reference.The app includes the basics of pressure measurement
XIVPressure Measurement

Pascal Law: Pressure Measurement
XV Capillary Rise
Capillary action (sometimes capillarity, capillary motion, or wicking) is the ability of a liquid to flow in narrow spaces without the assistance of, and in opposition to, external forces like gravity. The capillary action is due to the pressure of cohesion and adhesion which cause the liquid to work against gravity
XVICapillary Rise

Capillary Rise
XVIINewton's Law of Viscosity
Shear Stress on a fluid element is directly proportional to the rate of shear strain.The constant of proportionality is called the co-efficient of viscosity.
XVIIINewton's Law of Viscosity

Newton's Law of Viscosity