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In general, fluid mechanics is considered a branch of physics that studies the mechanics of fluids (liquids, gases, and plasmas) and the forces acting on them. Mechanical, civil, chemical, and biomedical engineering, geophysics, oceanography, meteorology, astrophysics, and biology are just a few of the fields where it can be used.

This is divided into two branches: fluid statics, which studies fluids at rest, and fluid dynamics, which studies the effect of forces on fluid motion. This is said to be a branch of continuum mechanics, a subject that models matter without using the information that it is made up of atoms; that is, it models matter from a macroscopic rather than a microscopic viewpoint. Fluid mechanics, particularly fluid dynamics, is just an active area of study that is typically mathematically complex. Many problems remain partially or completely unsolved and are best addressed numerically, typically using computers. This approach has given rise to a modern discipline known as computational fluid dynamics (CFD). Particle image velocimetry, an experimental technique for visualising and analysing fluid flow, also makes use of the highly dynamic nature of the fluid flow.

**Fluid statics**

Fluid statics, as well known as hydrostatics, seems to be the study of fluids at rest. This includes the study of fluids at rest in stable equilibrium, as opposed to fluid dynamics, which is the study of fluids in motion. Many everyday phenomena are explained by hydrostatics, such as why atmospheric pressure changes with altitude, why wood and oil float on water, and why the surface of the water will always level irrespective of the shape of its container. Hydraulics, the engineering of equipment for storing, transporting, and using fluids, is based on hydrostatics. Which also has applications in geophysics and astrophysics (for example, understanding plate tectonics and anomalies in the Earth’s gravitational field), meteorology, medicine (in the context of blood pressure), and many other fields.

**Fluid Dynamics**

Fluid dynamics is really a branch of fluid mechanics that studies fluid flow, or the science of liquids and gases in motion. Fluid dynamics provides a systematic structure that underpins these practical disciplines, embracing empirical and semi-empirical laws derived from flow measurement and applied to practical problems. A fluid dynamics problem is typically solved by calculating various fluid properties such as velocity, pressure, density, and temperature as functions of space and time. And it has many subdisciplines, including aerodynamics (the study of moving air and other gases) and hydrodynamics (the study of liquids in motion). Fluid dynamics does have many applications, including calculating aircraft forces and movements, determining the mass flow rate of petroleum through pipelines, predicting evolving weather patterns, understanding nebulae in interstellar space, and modelling explosions. Traffic engineering and crowd dynamics make use of some fluid-dynamical principles.

**FAQs**

##### What is the basic principle of fluid mechanics?

The fundamental fluid mechanics principles are really the continuity equation (i.e., mass conservation), the momentum principle (or momentum conservation), and the energy equation.

##### What is unsteady flow?

Unsteady flow can be considered as a flow in which the amount of liquid flowing per second is not constant. Unsteady flow is a passing occurrence. It could become steady or zero flow over time. For instance, when a valve at the pipeline's discharge end is closed.