Read about air | 61 Discussions | Page 1

  1. M

    I How do I read this equation for air friction/drag on an object?

    I am trying to understand an excerpt from an article describing the vibrations of a string (eg. guitar/piano) which reads as follows: This is basically the wave equation with Δm representing a small piece of mass from an interval of the string and two forces added to the right side. He...
  2. Emanuel Silva

    I Pressure generated by a column of air

    Applying Bernoulli, Does the term ρ*g*h matters ? Im trying to select a fan
  3. F

    B Sailboats providing their own wind

    I happened to be watching this cartoon and this one scene seriously bothered me... This... just feels like it wouldn't be a workable solution. Am I wrong? I can't say I perfectly understand how fans or propellers work, but I would imagine that by pushing air or water in one direction, equal...
  4. ChadThePianist

    COMSOL Modeling help (ambient air around a thermoelectric module)

    Hello everyone, I am wondering how to model ambient air around a thermoelectric module in COMSOL. I am fairly new to the software and am doing undergraduate research revolved around it. Any help or pertinent examples would be appreciated. I can send/post screenshots and or .mph files if it would...
  5. mktsgm

    I Sound through walls

    How and why do we hear through the brick walls? Does the sound actually penetrate the walls?
  6. S

    Bernoulli lift

    Homework Statement We have a plane which lift area is A=500 m2 and weight of plane is m= 540 000 kg. That the plane can stay in air the pressure difference between top and bottom of the lifts have to be: B>G --> Δp= (m*g)/A = 10 594.8 Pa. Homework Equations Bernoulli equation The Attempt at...
  7. prashantakerkar

    B Measuring the weight of gas in an inflated balloon

    What could be the method for measuring weight of gas in inflated balloon? Thanks & Regards, Prashant S Akerkar
  8. Fabrizio Vassallo

    I Weight of a box with a flying bird

    Hello! This is my first post here, and I look forward to many more! This is a sort of riddle I was told today, and left me full of doubts. So, the 'puzzle' was the following: " There's a man carrying behind his truck an enclosed trailer full of birds inside it. All the birds are standing on...
  9. C

    Air Displacement Pressure

    I am struggling with what seemed to be a simple problem and any help would be greatly appreciated. I have to determine the amount of pressure created when air is displaced buy gasoline flowing into a tank. The gas enters the tank at 10gpm. The entrance has a diameter of 1.5" and the vent has a...
  10. K

    Simulating scintillation (twinkling)

    hi all, i would like to set up a small lab experiment to try to create visible "terrestrial scintillation", whereby one can see fluctuations in air density (turbulent air), like the rear of the jet in this image: i have sketched a small setup before i begin; the test will send a projected...
  11. Suyash Singh

    Speed of airflow to lift a man

    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.
  12. C

    A Dieletric breakdown of air

    Although I have seen values such as 3 kV/mm for the dielectric breakdown of air, I was curious if there was an analytical or semi-analytical model of the ionization of say N2 under a uniform electric field. I am aware of Peek's law. Am I correct in assuming it is empirical? How might one connect...
  13. G

    I Air pressure holds coaster on glass: What if only half full?

    Hi. If I fill a glass with water up to the top and close it with a coaster, I can turn it upside down without the coaster falling off and spilling everything. Usually, this is explained with the atmospheric air pressure being bigger than the pressure of the water inside the glass (hence, it...
  14. A

    I Using an IR Thermal Gun to check for steam passing valves

    Greetings I am asking about the reliability of using a thermal gun to check if there is passing downstream the valve. The fluid is either steam or air. Wouldn’t the pressure and temperature drop sharply downstream the valve if it is closed but passing ? again I am talking about air or steam...
  15. S

    Confusion about Bernoulli's Equation & Airplane Wing

    Hi, I'm a little confused about the theory behind this problem related to fluids/Bernoulli's equation: "An airplane wing is designed so that the speed of the air across the top of the wing is 251 m/s when the speed of the air below the wing is 225 m/s. The density of the air is 1.29 kg/m3...
  16. G

    I Calculating the rate of rise of air

    I know there are many factors that affect this question, such as altitude etc, but in its simplest form....... - How fast does a parcel of air rise if, say, the parcel of air is at 5 degrees centigrade in a room filled with air at 0 degrees C. (Maybe I should be using Kelvin?). Just need to get...
  17. 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...
  18. K

    How to calculate : Mass flow of water vapor in the air (kg/h)

    Hello Homework Statement Lets say i have the given parameters: air volume flow : V = 36 m3/h Relative humidity: RH=33% air mixing ratio : X = 5.5 (1g H2O) / 1kg (DRY AIR) (calculated from RH) air temperature : T= 20 C So i know how much mass of water is the air compared to the air's "dry air"...
  19. A

    B Drag force and mass

    Why drag force doesn't Depend on the mass of the Object?
  20. A

    Brain fade/idiot moment - simple question about pipe flows

    Stupid question: I have the following pipe configuration: Working fluid = ambient air Pipe1 = 6 inch ID x 24 inch length Expansion1 = 2 inch length Pipe2 = 8 inch ID x 2 inch length Fan1 = assume 200 CFM @ 2860 rpm, 0.05 inH2O Contraction1 = 2 inch length Pipe3 = 6 inch ID x 12 inch length...
  21. B

    B Adding a nacelle in front or behind the fan?

    Can adding a nacelle in front or behind a standard pedestal fan affect the speed of the air coming in and out? If so, which is more beneficial: an intake nacelle or a nacelle in the front? Using Q=AV, with Q being constant because of the fan blade's max speed, can affecting the area (A) create...
  22. xpell

    Is diborane lighter or heavier than air?

    Hi, I have been reading about diborane (B2H6, a gas at standard conditions) and while the sources provide different density values (!), as in 1.2475 g/L at standard conditions, or 1.18 g/L at 15ºC and 1.216 g/L at 25ºC (sounds crazy?), all of them are lower than dry or moist air at the same...
  23. A

    Adiabatic compressed air and energy calculations

    Homework Statement . Consider a pump that is required to compress air in a factory. The cylinder in the pump has an inner diameter of 2.00 cm and length 60.0 cm. Air is drawn into the pump at atmospheric pressure and 18 degrees celcius and the pump adiabatically compresses the air to a pressure...
  24. C

    Electrical Efficiency of Ionized Air?

    Alright It's been over a year since I've posted and received amazing help the last time I did. Now I've a question I cannot seem to find an answer to. Say you have an electrical charge and use a transformer to step up the voltage high enough to where it arcs in air. Then you have a conductive...
  25. U

    Air Levitation Skis

    Are there any good research papers or established theories on using skis with either porous air bearings or an air skirt with holes to send pressurized air out? One of my concerns right now is the stability of a ski (ie any particular shape each ski/section should be and whether we should divide...
  26. R

    Calculating Pressure and Volume for an Air Cannon Tank

    Morning all, I am working on a Air Cannon Project and have hit a stumbling block. I am trying to work out what tank pressure and volume I would need to project a 1.4kg mass to 83m/s when it leaves the barrel. The barrel the mass will travel down is 4 meters long and 6inch in diameter, would...
  27. Robert James Liguori

    I Humid Air Density Forumulas

    I'm trying to compile a complete list of available humid air density formulas that work with air pressure, temperature and dew point (or RH). If you know any, please advise. Thanks, Robert
  28. S

    Automotive Air fuel ratio effects in diesel vs. petrol engines

    I'm a mechanic who is currently doing a study automotive engineering. Being someone who worked on both diesel and petrol cars I know what a higher or lower air fuel ratio (AFR) will do for both engines. However I don't fully understand how the following is possible. "Adding fuel in a diesel...
  29. Shariq Qazi

    Air Compressor Pressure vs CFM vs SCFM

    So my boss hook me up with the Compressed Air Calculations which we never did previously at our workplace. So started researching about the subject and designed a Compressed air system. The only thing i am not sure about now here is the relation between CFM vs SCFM vs Pressure. Let us take an...
  30. Tomimo

    Making bubbles and trying to use Trompe

    Hi, I am trying to create a device that would "simply" make a bubble under the water. What I am aiming for is production of small bubble but continuously and under the water. When I say continuously, it doeant have to be for extended periods of time, could be just for ~2 hours but the longer...