Airflow Definition and 112 Threads

Airflow, or air flow, is the movement of air. The primary cause of airflow is the existence of air. Air behaves in a fluid manner, meaning particles naturally flow from areas of higher pressure to those where the pressure is lower. Atmospheric air pressure is directly related to altitude, temperature, and composition.In engineering, Airflow or air flow is a measurement of the amount of air per unit of time that flows through a particular device.
The flow of air can be induced through mechanical means (such as by operating an electric or manual fan) or can take place passively, as a function of pressure differentials present in the environment.

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  1. druidhr

    HVAC Fan for tube 5" in diameter and 160ft long

    Hello, I have question about vent for tube that is 5" in diameter and 160ft long. Could 5" vent push/extract air to/from tube above? If possible, how much CFM should vent have? Thx 😊
  2. MiniITXTeam

    Best airflow for mini ITX PC case

    Hi friends. Nice to be a new member of that forum. Content and member knowledge are impressive. I was reading a lot about fan types and airflow physics when pulling and pushing air. My main idea is to do some test with different configurations of my setup. I'm going to measure temperature in...
  3. DaveC426913

    B Airflow around a vertical cylinder (such as a cigar)

    Writing from Cuba. This is canoeing: There are multiple causes for it but the one I'm interested in is when it is caused by directional air flow (AKA wind). If a breeze is blowing across my stogie from the same direction for an extended duration, one side will burn down much more than the...
  4. M

    Do Dual Fans Increase Radiator Efficiency More Than a Single Larger Fan?

    A while back, you guys helped me out with a project on my '69 Camaro. It was all about the Bernoulli principle and airflow taking the path of least resistance. I'm happy to say that the lower closeout panel I built (see pix below) seems to have done the trick as the car I no longer having any...
  5. B

    Misc. Airflow calculations for levitating a foam golf ball

    Im trying to find someone or a company who can do some calculations for me. I started with a fluid dynamics modeling company and they felt I would need a physics calculation. I need to a foam golf ball to be picked up by a column of air and held in place at aprox 10” until it is knocked off the...
  6. U

    Does a wing fly in its own downwash?

    Does wing really fly in already downward moving air? Video from 18:15 - 19:40
  7. L

    Help Me Design a Motorcycle Airbox for Charity Racing Series

    How did you find PF?: Google search Hello everyone, thanks for letting me join. I am hoping that some of you would be intrigued and help me design a new motorcycle airbox for a charity moped racing series here in the UK. We take the most common motorcycle ever made the Honda c90 and race it...
  8. S

    A few questions about airflow and filters...

    Just a few quick questions regarding airflow, mostly in connection with motors creating the airflow, like pc fans, vacuum motor, air going into a car engine through air filter, etc. 1) Adding more filters increases the availably surface through which the air can flow, therefor reducing the...
  9. Nick Nowaczyk

    I Wondering how much thrust a drone propeller generates

    I was wondering how fast you would need to spin a drone propeller to lift x amount of force and mostly how the rpm of the propeller affects the force of the airflow it releases. I’m incredibly new to physics in general and you can take everything I say with a grain of salt. I have no actual...
  10. Anachronist

    I Equalizing airflow through multi-hole orifices

    I know the Bernoulli equation for calculating the air velocity through a pressurized hole, but I am wondering if one hole of a given area behaves the same as multiple holes with the same total area. The Bernoulli equation doesn't make a distinction. Background: As a personal 3D design and...
  11. S

    Why does decreasing evaporator airflow impact an air conditioner's performance?

    The other day I read on a website that a lower evaporator airflow causes lower low pressure side saturation temperatures and higher delta T on an air-conditioner. Now I think I know why a lower evaporator airflow would cause a high delta T. If there is less air moving over the evaporator, the...
  12. F

    I Heat transfer via air cooling -- which airflow direction is best?

    I'm using a stainless steel pan and a fan to cool my coffee down as quickly as possible. Usually, I have the fan blowing down towards the coffee, but this morning I flipped it over to suck the heat out of the coffee and I'm wondering which of the two is the most efficient, especially as, in the...
  13. Al-Layth

    Calculating the change of a Wind Turbine's RPM due to Airflow as f(t)

    the tldr covers everything I think. I don't expect there will be an analytic solution here lol. but I don't even know where to even begin formulating this problem mathematically. I assume I should find an expression for the initial lift on the blades, multiply by 3 and then model it as a...
  14. J

    Can a Wing Truly Feel the Effective Airflow?

    Question is indeed very short and clear, but answer will eliminate many doubts and misleading conclusions. Theory predict downwash that will cause reduction in airflow angle,this we call effective airflow(airflow with lower angle compare at geometric AoA). Does wing of aircraft during flight...
  15. TheTuringTester

    Using the surrounding airflow to deduce the physics around UAP/UFO

    TL;DR Summary: Using the surrounding airflow to deduce the physics around UAP/UFO Now that NASA is in the mix for investigating UAP/UFOs - I started wondering at what their approach might be. I'm thinking they might be able to work from the outside in, toward the object/sensor(y) artifact...
  16. J

    Why Do Windward Tell Tales Stream Up in a Sail?

    This question is about sail aerodynamics, more precisely what cause spanwise airflow at the sails? When sailing close hauled,at the jib windward middle and top tell tales stream up or at 45 degress up, all others leeward and bottom windwards tell tales stream horizontaly. 1. What cause airflow...
  17. S

    Hospital Air Handler, Discharge Airflow vs. Static Pressure

    We have a new AHU installed for a Compounding Pharmacy. The unit has two return fans and two supply fans. They are installed in parallel and are powered by VFDs. In the event of one fan failing, the other fan is supposed to speed up to maintain static pressure in the clean environment. This...
  18. V

    Airflow thru 6 mesh, .035 gauge screen

    Happy Holidays! I saw your posting on airflow thru mesh screen and went to Perry's looking for answers. I haven't found what I'm looking for yet and was wondering if you can help? Our problem concerns bees coming down the chimney and how to stop them. We installed a Lymance chimney damper with...
  19. C

    How to determine mdot for choked airflow through a valve, given T,P

    Hello, I am working on a project that involves air at high pressure and temperature flowing through an orifice (valve) from one container to another. For each container, the volume, temperatures and pressures are known. The valve diameter is also known, and the fluid is air (which can be...
  20. I

    HVAC Redirecting Airflow with a Curved Surface

    I want to change the direction of airflow from a fan. The fan is covering a window so as to bring fresh air into the workspace, exhausting warmer air through open windows throughout the workspace. It would help cool those in the immediate area of the fan if it were blowing 90 degrees to the...
  21. T

    Measuring high velocity airflow

    I have a fan that consumes 60 W and blade diameter is 12 inch. If it's just 60% efficient, then the velocity of air coming out of it is around 9.5 m/s. I also have a nozzle inlet of which fits the fan and the diameter at the throat cum exit is 3.5 inch. I want to know how to measure the velocity...
  22. W

    Comparetto type Air Cleaner/Filter: What causes its increased airflow?

    Typical box fan+air filter setups use axial consumer-grade fans designed for providing maximum air flow at low power consumption. These fans do not provide sufficient air flow at the high static pressure requirements typical of air filters. The air filters DIYers use are high Merv(e.g Merv 13)...
  23. T

    Conversion of high velocity airflow into a pressure

    We know blower compressors i.e. compressors that use a blower to create high velocity for injecting air/fluid to higher pressure and that's available in market. Now, suppose we have such a blower type compressor that can create a flow of air/gaseous fluid of 337 m/s. Question is, what maximum...
  24. F

    B Help understanding the physics of airflow

    A melodica is a wind instrument that has a keyboard (piano-style, not computer-style). The player blows into the instrument. When a key is pressed, a passage opens. The air flows over a brass reed, making it vibrate. The reed sits in a channel a hair's-width bigger than the reed. The air flows...
  25. J

    Car in corner -- relative airflow

    http://mccabism.blogspot.com/2017/08/curved-flow-and-arrows-a3.html "The nose skirts on the Lotus 80 and Arrows A3 would have suffered from the fact that a Formula 1 car has to generate its downforce in a state of yaw. Thus, in a cornering condition, a car is subjected to a curved flow-field...
  26. P

    HVAC - Primary airflow temperatre

    Hi team, I am after some assistance. When I am amending the primary airflow temperature on diffusers from 22°C to 13°C, it is my opinion that all the Draught rating (DR) and comfort criteria calcs will all change as the air will become more dense. Is this correct?
  27. F

    How to determine the airflow due to a change in temperature?

    (Sorry for the really basic question. Been 20 years since high school physics and I've been working in a different industry)
  28. anorlunda

    Elevators & Airflow: The Impact of COVID-19 on Skyscrapers

    Elevators are a problem in this post COVID world. It is impossible to maintain social distancing while also meeting the passengers-per-hour needs of the building. Skyscrapers without efficient elevators are not practical. The new social etiquette says that it is OK to shut the door of the...
  29. areamer02

    How do peak flow meters measure flow rate?

    I am in pharmacy school and my professor recently went over lung diseases with us. An important (and cheap) tool that many patients can use to detect whether their lung function is declining is a peak flow meter, which tells the patient how much air they are moving when they exhale with as much...
  30. Frigus

    Aeroplane wing structure -- airflow question

    Why the air splitted at point a of aeroplane wing's cross section meet at point b simulatneously,
  31. R

    I Airflow direction -- Improving the cooling of my computer

    Hi, First of all I am sorry if I post in an incorrect thread. I can ask my question in PC forums but I thought it probably better if I ask in physics forum. So, I am trying to make the temperature in my PC better by adding additional fans, however I can't really place the fans in whatever...
  32. amare

    Airflow to Engine: What Happens if Air In Manifold < Cylinder?

    What-will-happen-if-the-air-entering-to-the-intake-manifold-is-smaller-than-the-air-entering-the-cylinder-from-the-manifold? the following expression is the rate of change of the manifold pressure interms of the mass flowing to the manifold and the mass of air flowing to the cylinder from the...
  33. WrathofAtlantis

    Could wing height position (through changing pitch) affect propeller airflow?

    I am talking about low wing single engine WWII fighter types. In particular, I am interested in accelerated propeller airflow through the transition/curvature of the prop slipstream spiral distribution around the wing, from being partly below, towards mainly above the wing. This as the wing's...
  34. NatanijelVasic

    I Subsonic and Supersonic Airflow Through a Constriction

    Hi everyone! For the past week I have spend a lot of time thinking about how de Laval nozzles work. But before I convince myself that I have understood it, I want to make sure that the (simpler) scenarios I describe below are correct. Setup: We have a long pipe with constant radius r = 1...
  35. S

    I Indirect Airflow for Safe Extraction of Hydrogen from Lead-Acid Battery Room

    Hello, I need to extract a flammable gas (hydrogen) from a lead-acid battery room. Is there a way to use a regular fan without putting it in the airflow (hence to produce some degree of negative pressure in the battery room)? I've made a little sketch to illustrate the actual situation...
  36. E

    Calculating airflow with pressure and diameter?

    Hi. Is there any way to calculate airflow out of a tube (into atmosphere) with only the pressure and cross sectional area of the tube?
  37. M

    Which fan/pipe combination is the most efficient?

    I'm making a ventilation system with a fan that will blow air through a 1700mm long pipe that has a 45 degree bent in the middle. I should decide on a pipe diameter of 125mm or 160mm. Also I need to choose between 3 different fans that has the following specs from the manufacturer: 120mm fan...
  38. Grey Area

    Plumbing How Can Airflow be Distributed Evenly in a Small Ducting System for 3D Printing?

    HI all. A bit out of my depth here...degree is in chemistry, but that's not helping me with the real world problem I'm trying to solve. I have a single air inlet that's being used as a cooling stream. It is channelled by a duct (or ducts, there are a few available designs) onto a piece of work...
  39. Suyash Singh

    Why Is the Calculated Velocity for Lifting a Person in a Wind Tunnel So Low?

    mass of air X velocity = mass of man x gravity (10000)x(v)=60x10 velocity=600/10000 how come velocity is so less? I am still in school so forgive me if my calculations look stupid.
  40. M

    Questions involving airflow and pressure around a car

    Homework Statement 1.Since the roadster seats only two people, it has only two side windows--one on each side. Each window is aligned squarely on the vehicle, so air can flow straight past the window as the vehicle heads forward. However, the air flowing around the roadster's windshield has to...
  41. F

    How to Fix Error: No Periodic Zones Adjacent to Grid Interface in CFD Fluent?

    I have created a savonius turbine model with 2 blades using 3D gambit. I want to simulate the flow of air flowing so as to drive the turbine savonius spin (unsteady, incompressible). Geometry consists of 3 volume boxes (domain tunnel flow), cylinder (domain grid interface), blade savonius...
  42. G

    Airflow Calculation Help: Velocity, Temp, Pressure, Diameter

    Hi, I am new to the use of forums and have no experience in airflow but I was looking for some help with the calculation of the gas flow through the main stack of a cement plant, the measurements I have at the moment are as follows Velocity= 12.5m/s Temperature= 120°C Differential pressure=...
  43. rumborak

    Increasing car efficiency by rerouting airflow?

    This is only a semi- serious thread, since I suspect there's a simple back-of-a-napkin calculation that shows this to be infeasible. The idea is the following: a lot of a car's efficiency gets lost in the form of air drag, I.e. forcing the air to go around the car. Could one upscale a...
  44. Carlos PdL SdT

    How Fast Does Air Escape from a Pressurized Suit into Space?

    I have a weird question here. At what speed does air flow from a pressurized container at one atm into vacuum (rupture in ISS for example). I was watching the Martian and I wanted to see how much deltaV Mark Wattney can get by puncturing his suit, so I did my homework and saw that the spacesuit...
  45. hovor

    Airflow and Preassure HW: Find Flow for Engine Needing 1m3/min

    Homework Statement Engine needs airflow of 1 m3/min (std. p=101.325kPa, T=293.15K) it is suplied by machine working at p=700kPa. Homework Equations How big flow is requied from the machine to supply engine with air? The Attempt at a Solution Tryed using ideal gas law pV=nRT 1) I found out n...
  46. C

    Airflow vs Flowrate: Are They Synonymous?

    Are these two terms synonymous? or not
  47. S

    Airflow Across a Persistent Cold Air Pool in a Basin

    This question is regarding the general fluid dynamics involving warm air advection aloft a persistent cold air pool in a small basin that is recessed in a horizontal planar surface. For scale, the basin has a compound parabolic shape, with a 30° viewing angle, a .146m radius at the base, a .292m...
  48. T

    Outdoor electronics casing. Airflow, condensation & temp.?

    I have a similar question as others but I felt wrong taking over their threads. The project is an casing for electronics that will be outside all year around. Built out of metal. This means rain, sun, snow. -20c to +35c. The electronics inside works only in 0c-45c and 10%-80% humidity. I want...
  49. J

    Calculating force input to air cylinder by airflow rate

    Hello there I'm having real difficulty with a problem to do with air cylinders and would really appreciate some help. I'm attempting to replicate the human breathing system in a simplistic form but I'm having trouble calculating the force required to provide the correct airflow rate at the...
  50. stoky

    I Airflow rate through a rectangular section

    I need to mount several rectangular orifices or sections on a wall with those two factors: - 20 Pascals differential pressure (negative pressure inside) - Inlet air speed 1100 feet per minute (5.58 meters per minute) I've got the section of each window, and the air caudal to renovate. I would...
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