# Pressure velocity and flow relationship quotes

### Introduction to Pressure Part II: Velocity, Flow Rate and Reaction Force | Valin

The relationship between velocity and pressure for incompressible flow ( constant fluid density) is given by Bernoulli's Law. Where v is flow velocity, rho is . Flow regime can also have influences on the case of flow velocity. less will be the pressure because force is directly proportional to pressure by relation P=F/A. To understand the relationship between the pressure drop across a pipeline and . Fluid velocity will change if the internal flow area changes.

**Bernoulli's Principle: High Velocity = Low Pressure**

As the velocity of the air increases the pressure also increases inside the pitot tube with respect to the ambient atmosphere. Note that the pitot must be pointed directly into the flow — if the tube is mounted at some angle to the direction of flow, the transducer will not sense the full pressure developed by the air velocity.

The pressure developed by the air velocity is called the velocity head, and it is affected by the density of the air. The density of the air, in turn, is a function of the local atmospheric pressure and the temperature. The equations that relate all these factors are: Note that to determine the air velocity the density must first be known.

This is the second equation and relates ambient atmospheric pressure and temperature to density.

## Introduction to Pressure Part II: Velocity, Flow Rate and Reaction Force

Assuming average conditions of 70 F and a barometer of If, for example, we measure a differential pressure from the pitot tube of 2. Air velocity is a function of air density and differential pressure, but determining air flow requires that the geometry of the piping be taken into account.

Note that it is still critical that the pitot tube be installed so that it is pointed directly into the oncoming flow stream. Ideally, determining the flow in terms of volume should simply a matter of multiplying the cross sectional area of the tube or duct by the air velocity.

If the dimensions of the ducting are known, then the cross-sectional area can be easily determined and the volumetric flow calculated.

Total Fluid Energy Daniel Bernoulli, a Swiss mathematician and physicist, theorized that the total energy of a fluid remains constant along a streamline assuming no work is done on or by the fluid and no heat is transferred into or out of the fluid.

The total energy of the fluid is the sum of the energy the fluid possesses due to its elevation elevation headvelocity velocity headand static pressure pressure head. The energy loss, or head loss, is seen as some heat lost from the fluid, vibration of the piping, or noise generated by the fluid flow.

### fluid dynamics - Relation between pressure, velocity and area - Physics Stack Exchange

Between two points, the Bernoulli Equation can be expressed as: In other words, the upstream location can be at a lower or higher elevation than the downstream location. If the fluid is flowing up to a higher elevation, this energy conversion will act to decrease the static pressure. If the fluid flows down to a lower elevation, the change in elevation head will act to increase the static pressure.

Conversely, if the fluid is flowing down hill from an elevation of 75 ft to 25 ft, the result would be negative and there will be a Pressure Change due to Velocity Change Fluid velocity will change if the internal flow area changes. For example, if the pipe size is reduced, the velocity will increase and act to decrease the static pressure. If the flow area increases through an expansion or diffuser, the velocity will decrease and result in an increase in the static pressure. If the pipe diameter is constant, the velocity will be constant and there will be no change in pressure due to a change in velocity.