- Shalmali

# Total pressure, Static pressure and Dynamic pressure!

Updated: Apr 23, 2021

How does Bernoulli's Principle play a role in it?

*Table of Contents:*

The world today due to the pandemic has changed!

No one believed that the world could run online, but it did survive. Which lead a lot of us to sit in front of our desks and work or study, this did not encourage us to move. But can you imagine what impact this can have on our blood flow? Let's see how it affects our body!

__Static Pressure:__

__Static Pressure:__

The term Static Pressure is used in fluid dynamics as the stationary fluid and the fluid in motion have different pressure.

The fluid which is stationary has Static Pressure.

The Static Pressure is generally termed as only Pressure which can be calculated by the formula;

When the fluid is stationary or the fluid near the walls of the flowing pipe has *Static Pressure*. The fluid molecules near the walls of the pipe have zero velocity. The reason for this is, the surface of the pipe (which has zero velocity) holds back the molecules of fluid that are near the walls due to friction between them. This phenomenon is called a *Boundary Layer*.

__Dynamic Pressure:__

__Dynamic Pressure:__

The flowing fluid has Dynamic Pressure.

For more details on dynamic pressure please check the __article__ here.

__Total Pressure (Stagnation Pressure):__

__Total Pressure (Stagnation Pressure):__

A very obvious relation between these pressures is:

Total Pressure (Stagnation Pressure) = Static Pressure + Dynamic Pressure

### How will we measure these pressures?

As shown in the image above; the static pressure is measured by placing a tube on the surface wall. The velocity of the fluid at the wall of the pipe is zero, in this way the static pressure can be measured.

The dynamic pressure cannot be measured directly, but we can measure total pressure. The total pressure is measured by placing a tube in the middle of the flow of fluid. In this way, the flowing fluid's (with velocity) total pressure can be measured. Then by the above formula, dynamic pressure can be measured!

### Let's consider an example:

When fluid flows in a nozzle (from 1 to 2), the area of the flowing fluid decreases. **The Total Pressure is constant throughout the fluid**. By continuity equation (Area * Velocity = constant), the velocity increases.

When velocity increases from point 1 to 2, by Bernoulli's Equation, the Pressure decreases. This pressure that is decreasing is Static Pressure and to balance the pressure the Dynamic Pressure increases. It can also be observed that when the velocity increases, the Dynamic Pressure will increase as the formula includes velocity as a parameter.

Coming back to the Blood Pressure, according to __Reuters__, due to long periods of sitting, blood pressure in the body increases. Blood pressure is dynamic pressure as the blood flows and has velocity.

**Summary:**

**Summary:**

The fluid which is stationary has Static Pressure.

The fluid which has velocity or fluid that flows has Dynamic Pressure.

Total pressure = Static pressure + Dynamic pressure.

The total pressure in any fluid remains constant.

If a fluid is flowing in a nozzle, the dynamic pressure increases and static pressure decreases.

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