What is fluid mechanics?

In the oil and gas industry, we are dealing with fluid mechanic problems every day. What is fluid? What is the nature and character of the fluid? To solve this problem we need to understand fluid mechanic basic. Mechanics is physics that deals with stationary objects and moves in the influence of forces.
1) Branches of mechanics that deal with stationary objects are called statics, and
2) The branch of mechanics that deals with moving objects are called dynamics

Fluid mechanics is the science that deals with the nature of the fluid in a state of silence (fluid statics) or fluid in a moving state (fluid dynamics), and the interaction of the fluid with solids or other fluids at the surface of its boundary. Fluid mechanics is often also called fluid dynamics by looking at silent fluid as a special case of fluid moving at zero speed. Fluid statics deal with silent fluid problems. Example: fluid in a glass, fluid in a pressure vessel, fluid in a reservoir, etc. Silent fluid is in equilibrium (the resultant force acting on it is equal to zero). In a silent fluid (fluid does not flow) there is no shear stress.

Fluid dynamics handles moving fluid problems, or commonly called flow. Flow occurs due to the resultant force acting on it is not equal to zero. Examples of flow phenomena can be found in everyday life, for example:

1. Water flow in the river body.
2. The flow of clean water in the piping system in Gathering Station.
3. Waste water flow in the drainage channel from Gathering Station.
4. The flow of hot steam from Boiler.
5. Earth’s atmosphere air (wind).
6. Fluid flow in all natural phenomena and man-made phenomena.

Fluid mechanics is divided into several categories, according to their developmental history, namely:

1. Hydrodynamics: the science of fluid motion which is practically incompressible such as fluids, especially water, and gas at low speeds. The hydrodynamic sub-category is hydraulics, which deals with the flow of fluid in pipes and open canals.
2. Gas dynamics: the science of fluid motion that experiences significant density changes, such as gas flow through the nozzles at high speeds.
3. Aerodynamics: the science of gas motion (especially air) through objects such as airplanes, rockets, and cars at high or low speeds.
4. Other special categories: meteorology, oceanography, and hydrology that deal with naturally occurring flows.

Mastery of fluid mechanics is essential for engineering team and engineers (physics, chemistry, machinery, nuclear, civil, etc.) because many problems (design, operation or maintenance) that are handled involve the flow of substances in the liquid or gas phase. A little description of the problem is flowed in:

• Engineering systems to reap energy from nature, for example, waterwheels, water turbines, wind turbines, and solar water heaters.
• Equipment to drive fluid flow, for example: for liquids are pumped and for gas are fans, blowers or compressors.
• Hydropower systems (Power plant), steam in power Plant, steam and gas power, geothermal power, and nuclear power.
• Passenger vehicles or goods on land (cars, trucks, buses, trains), in the sea (ships, submarines), and in the air (gas balloons, aircraft).
• The fluid transportation system for distributing clean water, distributing fuel oil and gas, collecting municipal wastewater.
• Process systems that are so often found in chemical industries that involve processes of combustion, mixing, stirring, heating, cooling, separation, etc.

There are five relationships that are most useful in fluid mechanics problems: kinematic, stress, conservation, regulating, and constitutive. The analysis of fluid mechanics problems can be altered depending on the choice of the system of interest and the volume of interest, which govern the simplification of vector quantities. By assuming that a fluid is a continuum, we make the assumption that there are no inhomogeneities within the fluid. Viscosity relates the shear rate to the shear stress. Definition of a fluid as Newtonian depends on whether the viscosity is constant at various shear rates. Newtonian fluids have constant viscosities, whereas non-Newtonian fluids have a non-constant viscosity. For most biofluid applications, we assume that the fluid is Newtonian.

application of fluid mechanics in oil and gas industry or Petroleum industry:

1. pressure and temperature measurement / calculation in pipeline from wellhead to Gathering system during project development
2. pressure and temperature measurement / calculation in pipeline during ILI activities
3. pressure and temperature measurement / calculation in pipeline design and pump selection during project phase. for example, we want to deliver or ship crude oil from gathering system to jetty.
4. flow rate measurement and daily monitoring
5. congeal prediction in pipeline