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i want to understand practically that what is difference between flow and pressure ? and how varies pressure and flow with pipe diameter if we change the diameter of the pipe ?

Originally Posted by PrajapatRK

i want to understand practically that what is difference between flow and pressure ? and how varies pressure and flow with pipe diameter if we change the diameter of the pipe ?

Pressure (the symbol: p) is the ratio of force to the area over which that force is distributed.

Pressure is force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure (also spelled gage pressure)[a] is the pressure relative to the local atmospheric or ambient pressure. While pressure may be measured in any unit of force divided by any unit of area, the SI unit of pressure (the newton per square metre) is called the pascal (Pa) after the seventeenth-century philosopher and scientist Blaise Pascal. A pressure of 1 Pa is small; it approximately equals the pressure exerted by a dollar bill resting flat on a table. Everyday pressures are often stated in kilopascals (1 kPa = 1000 Pa).


In physics, fluid dynamics is a subdiscipline of fluid mechanics that deals with fluid flow—the natural science of fluids (liquids and gases) in motion. It has several subdisciplines itself, including aerodynamics (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion). Fluid dynamics has a wide range of applications, including calculating forces and moments on aircraft, determining the mass flow rate of petroleum through pipelines, predicting weather patterns, understanding nebulae in interstellar space and reportedly modeling fission weapon detonation. Some of its principles are even used in traffic engineering, where traffic is treated as a continuous fluid.

Fluid dynamics offers a systematic structure—which underlies these practical disciplines—that embraces empirical and semi-empirical laws derived from flow measurement and used to solve practical problems. The solution to a fluid dynamics problem typically involves calculating various properties of the fluid, such as velocity, pressure, density, and temperature, as functions of space and time.

Before the twentieth century, hydrodynamics was synonymous with fluid dynamics. This is still reflected in names of some fluid dynamics topics, like magnetohydrodynamics and hydrodynamic stability, both of which can also be applied to gases.[1]

Dear Friend

Do not worry,I am explaining the two terms after that you will be able to know the exact difference between them

Pressure:

It is defined as the force per unit area applied perpendicular to the surface of an object.

>>The S.I unit is newton per square metre and that is called Pascal.

>> P=F/A:

where P=Pressure

>>F=Force

>>A:Area.

Pressure is a scalar quantity that is it has no direction and is a fundamental parameter in thermodynamics and is conjugate to volume.

Now coming to the flow:

Flow may have different meaning under different disciplines of science.

In fluid mechanics,water flow is defined as the measure of how much volume of water passes through a specific point per second.

>>It depends upon viscosity and speed of water.

>>Mass flow means movement of mass per time.

Hope the information provided by me will definitely help you in understanding the difference between them.

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All the best

aashisranjan784