# Fluid flow rate Definition and 20 Discussions

In physics and engineering, in particular fluid dynamics, the volumetric flow rate (also known as volume flow rate, rate of fluid flow, or volume velocity) is the volume of fluid which passes per unit time; usually it is represented by the symbol Q (sometimes V̇). The SI unit is cubic metres per second (m3/s). Another unit used is standard cubic centimetres per minute (SCCM).
In hydrometry, it is known as discharge.
In US customary units and imperial units, volumetric flow rate is often expressed as cubic feet per second (ft3/s) or gallons per minute (either US or imperial definitions).
Volumetric flow rate should not be confused with volumetric flux, as defined by Darcy's law and represented by the symbol q, with units of m3/(m2·s), that is, m·s−1. The integration of a flux over an area gives the volumetric flow rate.

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1. ### Misc. Why does the time between water drops change for my plant watering bottle?

[Mentor Note -- See post #2 for an attempt to clarify this thread start] Question I'd wondering what force make drop slow down? Does every time a drop push toothpick back into bottle? And of course how to solve it. Struct This is a bottle be pierced by a wooden toothpick, made for continually...
2. ### Engineering Flow through hinged hatch on inclined wall

So far I have only been able to come up with an equation for the flow (Q) using the orifice equation through the inclined area and thus not dependent on the angle. Can someone help me with an expression for this?
3. ### Volumetric flow of a overflowing cone

I solved the case where m=0.99999. Then the height at which it overflows can be obtained with the equation, when points on the liquid surface are chosen. Then the cross-sectional area is given by the circumference of the circle times the height that the parabola reaches, that cross-sectional...
4. ### How to find velocity of gas pump flowing into car tank

The general balance equation is as follow: d[m{u+gz+v2/2)sys=(u+gz+v2/2)dmin-(u+gz+v2/2)dmout +dq+dw. I understand that I would take in consideration the cross sectional area as well as the mass flow rate. However I can't figure out what else to consider as if atm pressure should be considered...
5. ### Inconsistent flow rate measurements of an engine diesel fuel

I am measuring the volumetric flow rate of a diesel fuel using "Turbines" flow meter, both in the supply and return fuel lines of an industrial diesel engine (https://www.cat.com/en_US/products/new/power-systems/industrial/industrial-diesel-engines/18398034.html – coupled with a generator for...
6. ### B Fluid Continuity Equation in different reference frame

If I have fluid with area 10 and velocity 10, if the velocity increases to 20 the area will become 5. But if we switch to a reference frame moving at velocity 1 opposite this motion, then it would be 10 and 11 to 5 and 21, violating the continuity equation. What is wrong?
7. ### Fluid flow rate calculation

I am trying to calculate the flow rate of O2 from a known volume 25 in^3. The cylinder will fill up to a maximum pressure of 140 psi in 11.26 seconds. Any help to determine the flow rate will be appreciated. Do I use Bernoulli equation to find the flow rate?
8. ### Concept subsea PHES system, /advice with calculations

I've created a concept design of a subsea pumped hydro storage system, and need to use the flow rate in order to calculate power output. I can calculate the energy storage capacity using ##E = mgh##: $$E = mgh = 25675000×9.81×200 = 50374 MJ = \frac {50374MJ}{3600} = 13992 kWh$$ I've attempted...
9. ### Pressure and heights of a manometer -- Find the fluid flow rate

Homework Statement Find the flow rate of water. The fluid in the manometer is mercury. ##d_{1},d_{2}## are the diameters in the figure Homework Equations Bernoulli, continuity equations The Attempt at a Solution We know that ##p_{1}=p_{1Top}+\rho_{water}gh_{2}##...
10. ### Water reach (Hose without and with a nozzle)

Homework Statement A hose of inside diameter ##1.5cm## can reach a distance of ##1.5m##. A nozzle is inserted in the hose and water can now reach ##24m##. What is the inside diameter of the nozzle? The height is the same in both cases. Homework Equations Use continuity equation...
11. ### I Was the recent ISS leak imminently dangerous?

The ISS suffered a leak apparently caused by a 1/8 inch hole left during manufacture and never repaired. On Quora, the claim has been made that such a hole with one atm of pressure difference would only cause 324 cu ft of air to rush out per hour. I don't think this is close to correct, but I am...
12. ### Business major.... fluid dynamics question....

Homework Statement I have a syringe filled with water. This syringe is a cylinder with a length of 3 inches (L), diameter of 1.5 inches (D). Attached to the syringe is a constant force spring, which pushes the plunger into the syringe with a force of 2 pounds (F). Ignore the friction between...
13. ### Lift equation and pressure coming out of a tube?

I am making a small project at home for my solar panels. I have made a similar project when I was in school but I can't remember the equations. I want to attach an air compressor to a tube then install it on top of a solar panel, and pinch a few holes in it to clean the dust that accumulates...
14. ### Water flow from pressurized tank - versus temperature

Bernoulli's equation gives us this as the flow rate from a pressurized tank: $$v = C_v \sqrt{2gh + \frac{p}{\rho}}$$ where ##C_v## is the velocity coefficient, ##g## is the acceleration due to gravity, ##h## is the height of the water above the exit hole, ##p## is the excess pressure above...
15. ### Would the velocity of a fluid increase right after exiting a pipe into open air?

If you have an non-viscous incompressible fluid flowing in a pipe whose static pressure is higher than atmospheric pressure, then after exits the pipe will the dynamic pressure increase? The static pressure of the fluid right after exiting should decrease because it should be equal to the...
16. ### Jet Spread Rate K Values- Momentum diffusement

The Problem Statement I have a jet entering leaving a nozzle at ui into an ambient fluid with ue = 0 I am trying to equate the rate of momentum diffusement (or spread) to the shear forces caused by ue -ui I understand that the rate momentum diffusement is are equated by empirical K- values...
17. ### Calculation of water flow rate in heat exchanger

I am not a mechanical engineer; but I have physics background. I want to lift about 250 watts of heat from a metal block. At the same time I have to maintain its temperature at 30 deg Cel. For this I want to use water-air heat exchanger (HE). Heat exchanger will have inlet & outlet pipes. Hot...
18. ### Bernoulli equation with losses dilemma

Homework Statement Hello,Could you please lend me a hand with this problem?I would really appreciate it. Question:[/B] Their Answer: KL=2*0.75(2 elbows) D=5*10^-2 m ;f=0.001(fanning friction factor) Assumptions I made: Point 1 which is at the top of the liquid in the tank: h1=23 m...
19. ### Help with water pump calculations

So i have this Diesel Water pump, i need to achive a pressure of 4 bars at the end of the hose, How to calculate the pressure in inlet to achieve the desired result of 4 bars at outlet. (Assuming that I'm using a standard hose of length 30metres, with a diameter of 2.5 inches) Pump FLOW RATE IS...
20. ### Volume Flow Rate and Pressure

Homework Statement Question: For a fluid flowing within a horizontal tube, if the diameter of the tube narrows, will the fluid's flow rate increase, resulting in increased pressure in the narrowing and explain your reasoning. Homework Equations Volume flow rate = volume/time Volume = Area x...