Flow rate and velocity relationship

Flow Rate and Its Relation to Velocity - Physics LibreTexts

flow rate and velocity relationship

Flow rate indeed is constant, but somehow velocity may be reduced. Flow regime can also have influences on the case of flow velocity. A graphic showing flow through a nozzle with the mass flow rate equation for If the fluid initially passes through an area A at velocity V, we can define a volume. The rate of reaction, often called the "reaction velocity" is a measure of how fast a reaction occurs. As a reaction proceeds in the forward.

Calculating Volume from Flow Rate: The Heart Pumps a Lot of Blood in a Lifetime How many cubic meters of blood does the heart pump in a year lifetime, assuming the average flow rate is 5.

Volumetric flow rate - Wikipedia

For comparison, this value is equivalent to about times the volume of water contained in a 6-lane m lap pool. Flow rate and velocity are related, but quite different, physical quantities.

flow rate and velocity relationship

To make the distinction clear, think about the flow rate of a river. The greater the velocity of the water, the greater the flow rate of the river.

flow rate and velocity relationship

But flow rate also depends on the size of the river. A rapid mountain stream carries far less water than the Amazon River in Brazil, for example. This equation seems logical enough.

The relationship tells us that flow rate is directly proportional to both the magnitude of the average velocity hereafter referred to as the speed and the size of a river, pipe, or other conduit.

12.1: Flow Rate and Its Relation to Velocity

The larger the conduit, the greater its cross-sectional area. Because the fluid is incompressible, the same amount of fluid must flow past any point in the tube in a given time to ensure continuity of flow.

  • Volumetric flow rate

In this case, because the cross-sectional area of the pipe decreases, the velocity must necessarily increase. This logic can be extended to say that the flow rate must be the same at all points along the pipe. The consequences of the equation of continuity can be observed when water flows from a hose into a narrow spray nozzle: Conversely, when a river empties into one end of a reservoir, the water slows considerably, perhaps picking up speed again when it leaves the other end of the reservoir.

In other words, speed increases when cross-sectional area decreases, and speed decreases when cross-sectional area increases. When a tube narrows, the same volume occupies a greater length. For the same volume to pass points 1 and 2 in a given time, the speed must be greater at point 2. The process is exactly reversible. If the fluid flows in the opposite direction, its speed will decrease when the tube widens.

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.

What is volume flow rate? (article) | Fluids | Khan Academy

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.

As an example, if an expansion fitting increases a 4 inch schedule 40 pipe to a 6 inch schedule 40 pipe, the inside diameter increases from 4. If the flow rate through the expansion is gpm, the velocity goes from 9. The change in static pressure across the expansion due to the change in velocity is: In other words, pressure has increased by almost 0.

flow rate and velocity relationship

Pressure Change due to Head Loss Since head loss is a reduction in the total energy of the fluid, it represents a reduction in the capability of the fluid to do work. Head loss does not reduce the fluid velocity consider a constant diameter pipe with a constant mass flow rateand it will not be effect the elevation head of the fluid consider a horizontal pipe with no elevation change from inlet to outlet.