What is Capillary: Definition and 113 Discussions

A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter, and having a wall one endothelial cell thick. They are the smallest blood vessels in the body: they convey blood between the arterioles and venules. These microvessels are the site of exchange of many substances with the interstitial fluid surrounding them. Substances which cross capillaries include water, oxygen, carbon dioxide, urea, glucose, uric acid, lactic acid and creatinine. Lymph capillaries connect with larger lymph vessels to drain lymphatic fluid collected in the microcirculation.
During early embryonic development, new capillaries are formed through vasculogenesis, the process of blood vessel formation that occurs through a de novo production of endothelial cells that then form vascular tubes. The term angiogenesis denotes the formation of new capillaries from pre-existing blood vessels and already present endothelium which divides.

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  1. S

    Solving the Problem of Capillary Action in Tiny Peristaltic Pumps

    Hello, I designed a tiny peristaltic pump which works really fine. I am using a very thin tubing of 0.5mm diameter, which makes me struggle with capillary action, unfortunately. When my pump is not working, sometimes liquid still flows into the tubing because of capillary action. Do you have...
  2. Talal

    Measuring the critical capillary number

    Is there a way to measure the critical capillary number? I am running water flooding tests in micro single capillary ducts. I am displacing oil in my experiment, and my channel should be oil wet. I was able to measure the properties of both fluids, this includes; Kin and Dyn Viscosities...
  3. M

    A Confusion of the scale of contact line dynamics and capillary flow

    I'm having some trouble getting my head around the scale at which capillary flow and contact line dynamics are important. In the simple case of liquid rise in a capillary tube, a smaller tube will allow for greater rise since a larger height is required to achieve an equal weight of the liquid...
  4. Nick tringali

    How does capillary action of a liquid not violate energy conservation?

    I am learning about capillary action of water. As water moves up paper. How is that not violating energy conservation as it is going against the force of gravity. This obviously can't be infinite energy.
  5. T

    Is this a valid way to calculate capillary force / pressure?

    When figuring out the capillary pressure on a liquid in a tube of a certain cross-section, the typical approach is to consider the Young-Laplace pressure and the curvature etc. I was looking through some of my old notes and I had an equation for the capillary force: fc = γ cosθ dS/dx where γ...
  6. B

    Capillary action, evaporative pumping or bio-mechanical pumping....

    I was researching capillary action to design an efficient evaporative cooler, when I found this thread... https://www.physicsforums.com/threads/using-capillary-action-to-raise-water-is-perpetual-flow-possible.551285/ Upon reading this thread, the statement, "Trees are solar driven evaporative...
  7. harsh22902

    Surface Tension and Capillary Rise

    According to this definition I am unable to understand why does surface tension acts tangentially to surface of contact of liquid and capillary tube. And is the force of surface tension balancing the adhesive forces which lead to capillary rise OR it is the reason behind the capillary rise?
  8. M

    A Gravitational - Capillary waves

    Please, I need a good books about the meaning of "Gravitational and Capillary waves "
  9. Rituraj131

    Maximum Capillary Rise: Dynamic Treatment of Liquid in Motion?

    I know that the height in general is goven by 2σcos(θ)/(ρgr). So the maximum height can be 2σ/(ρgr) with cos(θ)=1. But the answer given is c.
  10. A

    Calculating surface tension with the Capillary Equation

    Homework Statement Hello everyone, I am doing an experiment and I've hit a snag with my calculations. I am looking at how concentrations of soap affect surface tension in water. I am have been using the capillary equation and capillary tubes for my calculations. I have practiced this method for...
  11. Navin

    Capillary Tube Behavior in a Gravityless Environment

    Homework Statement A 20 cm long capillary tube is dipled in water.The water rises up to 8cm .if the entire arrangement is put in a freely falling elevator ,the length of the water column is A)10cm B)8cm C)20cm D)4cm Homework Equations Its a theoretical sum The Attempt at a Solution...
  12. A

    B Why does mercury rise in a glass capillary tube despite its strong cohesion?

    It's a question which come into my mind after reading related notes now and again and I can't think of plausible response to it. Given Statements: We have a container filled with mercury and a glass capillary tube placed in it . As tube's diameter become smaller mercury's height in tube will get...
  13. C

    Microfluidics in pressures lower than one atmosphere

    Hi everyone I am trying to build an experiment with microfluidics. I have a reservoir containing a bellow. This bellow is a compensation mechanism and makes sure that the liquid (in this case water) can be pushed out of the reservoir. Before storing the fluid in the reservoir, the reservoir is...
  14. Foreverlearning

    I The role of capillaries in a dilution refrigerator

    I've been trying to understand how dilution refrigerators work and inbetween intermediate steps, between different temperature points, I see capillaries here and there under the name of impedances. After some googling, I somewhat convinced myself that it's to build up pressure before and after...
  15. M

    Possible webpage title: Does Increased Inertia Lead to Higher Capillary Numbers?

    Hi PF! The capillary number is defined as ##Ca = \mu V/\sigma##. Does more inertia in a fluid increase the capillary number? As inertia increases, it's my intuition that so does velocity. Then it seems (all else constant) that ##Ca## increases too. Is this correct?
  16. D

    I Adhesive Forces: Bigger vs. Smaller Straws

    Is the adhesive force greater in a smaller tube then a bigger tube at the top? So would it take more energy to take out water at the top of the straw from the thinner straw? Or would, due to gravity cancelling eventually the capillary rising, the adhesive force at the very top of the straw is...
  17. S

    I Is there a frequency cutoff for Debye theory of capillary waves?

    I calculated the energy density of capillary waves with Debye method (pretty much Debye model in 2D), and I assumed there is a frequency cutoff for capillary waves as well. However, when I checked my work with solution I was quite surprised that the solution suggests there is no such a cuttoff...
  18. M

    Which software do you recommend for capillary channel flow?

    Hi PF! I'm trying to model a fluid dynamics problem where there is flow in a wedge. Length scale is 160mm and two fluid phase: air sits on top of silicone oil. Boundary conditions can be to specify height conditions, flow rate, et cetera. Very low gravity, so surface tension is very relevant...
  19. D

    Does capillary action use water heat energy?

    Capillary action is a form of work, i.e. an object (water) moved by a force (capillary action) over a distance. Since all work requires energy, what supplies the energy for capillary action? Is the chemical energy of the water increased by adhering to a surface? Perhaps the heat energy of the...
  20. K

    How does the capillary tube in refrigerators work?

    How does the capillary tube decrease the pressure on the liquid when its diameter is smaller? How small diameter of capillary tube is helpful in causing more pressure drop? And how, when pressure drops, the liquid instantly cools down?
  21. T

    Pore pressure due to capillary rise

    Homework Statement Why there's no pore pressure due to capillary rise at point A and point D ? There's only pore pressure due to capillary rise at B .. Homework EquationsThe Attempt at a Solution i think the author is wrong . There's should be also ore pressure due to capillary rise at A and D...
  22. G

    Capillary and liquid tension problem

    Dear all, I have a problem to solve but i am not very familiar with physics. See attached image. Data: 1)I have a capillary system with a short an thinner tube on one end and larger taller tube communicating. 2) at the equilibrium, the thinner capillary is full of liquid, while there is a...
  23. P

    FEM Analysis of Hagen-Poiseuille Law Pressure Distribution

    Hello, I am doing a project which includes attempting to map a theoretical pressure distribution across a capillary tube. I am trying to do a finite element analysis using Hagen-Poiseuille's Law to map the theoretical pressure distribution before I move onto using a SolidWorks Flow Simulation...
  24. A

    Do the radius of capillary affect the value of surface tension ?

    While going through the derivation to find the surface tension of liquid i came with the formula which says that the surface tension is directly proportional to radius of the capillary so does that imply if we use a capillary with a greater radius so the same will give the different value of...
  25. Omish

    Water in capillary tube and friction

    When we put an empty capillary tube in a water container, the water goes up a little bit by itself until the surface tension (ST) force is equal to its weight .This shows that unlike friction, this ST force acts individually . So if we take out the tube out of the container, and drain a little...
  26. N

    I Does Capillary Flow in a Tube Create a Pressure Gradient?

    I'm trying to understand capillary flow in a tube. I've found this http://folk.uio.no/eaker/thesis/node11.html that explains some aspects of it, the system is illustrated here, So the (black) non-wetting fluid resides to the left and the (white) wetting fluid is to the right. Say that we are...
  27. D

    High Capillary Length Materials: 1cm+ Easily Found

    Which materials have high capillary length, and can be found easily? (above 1cm)
  28. P

    Finding the number of moles of an ideal gas in a capillary

    Homework Statement The temperature across the capillary with constant cross-sectional area and length L is given by ##T=T_0e^{-kx}##. Assuming an ideal gas and constant pressure show the number of moles to be: $$n=\frac{PV(e^{kL} - 1)}{RkLT_0}$$ Homework Equations ##PV=nRT## The Attempt at a...
  29. Hanyu Ye

    I The difference between capillary number and Laplace number?

    It seems that both the capillary number and the Laplace number represents the relative effect of viscous forces and surface tension. Can anybody explain the difference between them? Thanks a lot. I have attach the Wikipedia- links to these two concepts...
  30. Y

    How to Calculate Capillary Rise on the ISS

    Homework Statement Consider an experiment on the International Space Station, which is illustrated below. A cylindrical capillary of length L= 10. [cm] and inner diameter of dc=500. [µm] (sealed at one end), is positioned to contact a droplet of water, D = 1.0 [cm], which is floating in the ISS...
  31. C

    Measuring Height of Meniscus in Capillary Action

    I've been reading up on capillary action in a tube, and I have some questions: Say we insert a tube in a pool of fluid; Jurin's Law expression is ##h=\frac{2\sigma \cos \phi}{r\rho g}##. However, this height is not the height of the fluid measured from the bottom of the tube, but rather the...
  32. I

    I Capillary Action: Overcoming Capillary Force with Ions

    Hello So like anyone who read about capillary action, you think about free energy generation, but as I read the problem is that the water won't leave the capillary tube on the other side because of the capillary action. So you need to use the capillary force from one end of the tube then...
  33. fargoth

    Viscosity -- capillary radius, and permeability threshold

    In a demonstration of the qualities of liquid Helium in type 1, and type 2 the fact that a super-fluid can permeate through capillaries which are too small for type 1 Helium to pass through. I was wondering about the equation which determines the capillary radius threshold under which the...
  34. SDewan

    Capillary rise in tube of insufficient length

    When there is Capillary rise in tube of insufficient length, why does not the liquid overflow?
  35. Alfreds9

    Capillary action speed formula?

    Hi, I was looking for a formula to describe capillary action speed in a medium. On wikipedia (https://en.wikipedia.org/wiki/Capillary_action) I came across a formula which describes the cumulative volume of a liquid drawn by capillary action after time t where V is cumulative volume, A is...
  36. S

    Capillary action at different temperatures

    Hi guys, I'm doing a project at the moment revolving around capillary action and surface tension. Today I conducted an experiment to observe capillary action in a capillary tube and paper towel at different temperatures of water. I don't understand why I've got the following results: As you...
  37. E

    Flow of gases through a capillary

    You have a capillary with a stream of water vapor flowing through. Inside the capillary argon gas is also flowing (in the same direction) with a flow rate of 3 L/min. How high of a flow rate can the water vapor have before it starts condensing on the walls? Flow is laminar and the system is at...
  38. dark knight13

    What happens if we put a hole in a capillary tube?

    case 1)The hole is drilled before the liquid rises case 2) the hole is drilled after the liquid rises
  39. AdityaDev

    What are the variables that affect the pressure of a gas in a capillary tube?

    Homework Statement Homework Equations height of liquid above water level ##h=\frac{2T}{R\rho g}## for isothermal process :##PV##=constant And if ##P_0## is atm. pressure, and P is pressure just below the water level in capillary tube, then $$P=P_0-\frac{2T}{R}$$ The Attempt at a Solution...
  40. Y

    Capillary Action, Are there structures that aid it?

    Hello, I'm an art student trying to recreate this phenomenon, but maybe on a larger scale. I'm trying to create a sculpture that is able to do that. If I can rely on just structure and not worry about materials, that would be great, since my plan is to be able to 3D print it out of plastic...
  41. M

    Capillary Action Homework: ΔP, γ, R1, R2

    Homework Statement Kindly view the attached. Homework Equations ΔP = γ(1/R1 + 1/R2) The Attempt at a Solution [/B] I've began the topic of fluid mechanics, capillary pressure, surface tension and such and was given this question to try. Now from my limited knowledge it seems to me that in...
  42. F

    Shear viscosity and Capillary Rheometer

    Hello Forum, I have some conceptual doubts about shear viscosity and would like some help if possible. In general, viscosity depends both on temperature and on shear forces (more strongly on shear forces). "Shear viscosity" is the viscosity that a molten plastic assumes when the molten fluid...
  43. L

    Preventing Capillary Action in Hot Chamber Wire Feed-throughs

    I have a strange problem. We test our components in oil in a hot chamber(60-100C). Wires are bought out of the chamber for power supply and data acquisition. The oil from the chamber leaks on to the wires because of heat and capillary action. This makes the wires oily and working with oily wire...
  44. J

    Capillary Rise in Tube: What Happens if Length is Insufficient?

    What happen when the capillary rise occur in a tube of insufficient length? My teacher told me that hR = constant where h is height and R is radius of sphere of which the curved surface of meniscus firm a part. She also told me that if h become less so R has to increase so radius of meniscus...
  45. R

    Why Aren't Pressure Differences Included in Capillary Filling Dynamics?

    When we write the equation for expressing the dynamics of capillary filling, why don't we include the effects of pressure difference?
  46. B

    Volume flow through a one side closed capillary

    Hi everyone, I'm doing a simulation and need some help. A capillary which is closed on both ends with the length l (x=0 to x=l), with a radius R and the volume pi*R^2*l is dropped on a parachut at the time t=0 from a hight h above ground. At t=0 the pressure inside the capillary is p_i0 (this...
  47. H

    Surface Tension vs. Capillary Force

    What's the difference between surface tension and capillary force? Surface tension, a tensor, is the force per unit length. Again surface energy is the energy required to increase the surface area by one unit. Is the surface tension a capillary force?
  48. C

    Calculating Capillary Amount Given Aorta Blood Flow

    Homework Statement When the rate of blood flow in the aorta is 5 litres per minute, the speed in the capillaries is about 0.33 mm per second. If the average diameter of a capillary is 8 microns (0.008 mm), calculate the number of capillaries in the circulatory system. Homework Equations Flow...
  49. L

    Fluid dynamics problem -- Tanks Connected by Capillary

    Homework Statement Two tanks are connected via a capillary pipe, with one tank over the other. The speed in which the liquid flows from the upper tank to the lower tank is 3472 cm/min. The height of the liquid inside the upper tank is 30cm from the bottom of the tank. The capillary pipe sticks...
  50. D

    Capillary action with respect to "wicking beds"

    Good day I am interested in making a wicking bed for typical vegetable growing. I have read that the height of the soil should be no higher than 300mm. I suspect this number is experimental or simply copied from other sources. I am a little more curious regarding the mechanics of such a...
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