Name: capillary action in narrow spaces
Uploaded: 2025-02-13T15:43:08.000Z
Duration: 1 min 19 s
Channel: JoVE

La capillarità si riferisce al movimento del liquido in spazi ristretti, guidato dalla tensione superficiale e dalle forze di attrazione tra il liquido e le superfici vicine.
Tale movimento è comunemente osservato in tubi sottili, materiali porosi e altri piccoli spazi.
Quando un tubo stretto, chiamato tubo capillare, viene inserito in un liquido, il livello del liquido può aumentare o diminuire a seconda dell'interazione delle forze.
Quando le forze adesive tra il liquido e il tubo sono più forti delle forze coesive all'interno del liquido, il liquido sale, il che è chiamato aumento capillare.
D'altra parte, se le forze coesive sono più forti, il liquido cade, provocando una depressione capillare.
Diversi fattori che influenzano l'altezza alla quale il liquido si muove in un tubo capillare sono l'angolo di contatto tra il tubo e il liquido, la tensione superficiale del liquido, la densità del liquido, il raggio del tubo e l'effetto della gravità.
La capillarità è importante sia nei processi naturali che nella tecnologia, in quanto aiuta il trasporto dell'acqua nelle piante, l'assorbimento dei liquidi nei materiali porosi e le tecnologie come i dispositivi microfluidici.

capillarità nei fluidi

La capillarità, definisce il movimento compiuto da un liquido in piccoli spazi, senza che vi agiscano forze esterne. Questo fenomeno è guidato dalla tensione superficiale e dalle interazioni adesive tra il liquido e le superfici solide circostanti; è spesso osservato in tubi stretti, materiali porosi e particelle fini.

La tensione superficiale è fondamentale per la capillarità. Questa, deriva dalle forze coesive tra le molecole liquide al confine liquido-aria, che formano una pellicola resistente alle forze esterne. Quando il tubo capillare viene immerso in un liquido, il livello del liquido cambia in base alle interazioni adesive tra il liquido e la superficie del tubo. Se queste forze adesive sono maggiori delle forze coesive del liquido, il liquido sale nel tubo, attuando la cosiddetta risalita capillare. Se le forze coesive sono più forti, il livello del liquido scende, determinando depressione capillare.

L'altezza a cui il liquido sale o scende in un tubo capillare, è influenzata da diversi fattori, tra cui la tensione superficiale e la densità del liquido, l'angolo di contatto tra il liquido e il tubo, l'accelerazione gravitazionale e il raggio del tubo.

La capillarità è coinvolta in molti processi naturali e industriali. Influisce sul movimento dell'acqua e dei nutrienti presenti nel suolo, ed è quindi essenziale per la crescita delle piante. Nei materiali porosi, influisce sull'assorbimento e la ritenzione dei liquidi. La capillarità è anche utilizzata in tecnologie come la stampa a getto d'inchiostro e la microfluidica.

Capillarità nei Fluidi

La capillarità si riferisce al movimento del liquido in spazi ristretti, guidato dalla tensione superficiale e dalle forze di attrazione tra il liquido e le superfici vicine.
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Education

Didattica

JoVE Core

Civil Engineering

Ingegneria Civile

Unit 1

Unità 1

Fluid Properties

Proprietà dei fluidi

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

Capillarity in Fluid

capillary action in narrow spaces

Capillary action is the movement of liquid through narrow spaces without any outside force. It depends on surface tension and adhesion between the liquid and nearby solid surfaces. This effect is common in narrow tubes, porous materials, and fine particles.

Surface tension comes from cohesive forces between liquid molecules at the liquid-air boundary. These forces create a thin skin that resists outside pressure. When a capillary tube is placed in a liquid, the liquid level changes because of its interaction with the tube surface.

If adhesion is stronger than cohesion, the liquid rises in the tube. This is called capillary rise. If cohesion is stronger, the liquid level drops. This is called capillary depression.

The amount a liquid rises or falls depends on several factors. These include surface tension, liquid density, the contact angle with the tube, gravitational acceleration, and the tube radius. Capillarity matters in nature and in technology. It helps move water and nutrients in soil for plant growth, affects liquid absorption and retention in porous materials, and is used in inkjet printing and microfluidics.

Capillary Action in Narrow Spaces

characteristics of fluids

Fluid Behavior in Liquids and Gases

Fluids include liquids and gases, and they behave differently from solids because of how their molecules are arranged. In solids, molecules are tightly packed and held by strong intermolecular forces. That structure helps solids keep their shape and resist deformation. Fluids have molecules that are farther apart and held by weaker forces. Because of this, they can flow and change shape easily. A fluid is any substance that deforms continuously when shearing stress is applied. Shearing stress...

density, specific weight, specific gravity and compressibility of fluid

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Fluid Properties: Density, Weight and Compression

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viscosity of fluid

How Temperature Changes Fluid Viscosity

Viscosity describes how much a fluid resists flow and deformation. It comes from internal friction between fluid layers that move past each other. Dynamic viscosity, shown by the Greek letter mu (μ), measures the force needed to move one layer over another. Newtonian fluids, such as water and air, have a linear relationship between shearing stress and the rate of shearing strain. Their viscosity stays constant, even when the applied stress changes. Non-Newtonian fluids, like ketchup,...

types of fluids

Newtonian vs Non-Newtonian Fluid Behavior

Fluids can be grouped by how they respond to shear stress. Shear stress is a force that acts across a material, and shear strain rate describes how quickly it changes shape or flows. In this lesson, fluids are divided into Newtonian and non-Newtonian types. Newtonian fluids follow Newton’s law of viscosity. Their shear stress changes in a linear way as the shear rate changes. That means their viscosity stays constant, so their flow is predictable and easier to analyze. Water, air, oil, and...

newtonian fluid: problem solving

Newtonian Fluid Viscosity and Shear Stress

Newtonian fluids have a constant viscosity, so their shear stress and shear strain rate stay directly proportional. This creates a linear, predictable link between force and flow. Water, air, and light oils are common examples of Newtonian fluids. A simple way to study this behavior is to place the fluid between two parallel plates. One plate stays still, and the other moves at a constant velocity. The fluid forms a velocity gradient, which is the change in speed across the distance between...

vapor pressure of fluid

Vapor Pressure and Boiling Behavior

Vapor pressure and boiling behavior are closely linked in fluids. Vapor pressure is the pressure a vapor exerts when it is in thermodynamic equilibrium with its liquid at a given temperature. It shows how strongly molecules tend to leave the liquid surface and move into the vapor phase. A closed container helps show how vapor pressure forms. If a liquid sits in a sealed space with a small air gap, and that space is evacuated, vapor molecules escape from the liquid into the empty space. The...

surface tension of fluid

Why Water Drops and Needles Float

Surface tension helps explain why water forms drops, supports small objects, and moves in thin tubes. It is a property of fluids at the boundary between a liquid and a gas, or between two immiscible liquids. At the surface, molecules are pulled inward by neighboring molecules. That inward pull makes the surface act a little like a stretched elastic membrane. Inside a fluid, molecules are attracted in all directions. Surface molecules do not have the same balance of forces. They feel a net...

capillarity in fluid

Capillary action is the movement of liquid through narrow spaces without any outside force. It depends on surface tension and adhesion between the liquid and nearby solid surfaces. This effect is common in narrow tubes, porous materials, and fine particles. Surface tension comes from cohesive forces between liquid molecules at the liquid-air boundary. These forces create a thin skin that resists outside pressure. When a capillary tube is placed in a liquid, the liquid level changes because of...

design example: deciding thickness of lubricating fluid in a shaft

design-example-deciding-thickness-of-lubricating-fluid-in-a-shaft

Lubricant Film Thickness for Shaft Bearings

Lubricant film thickness for shaft bearings is calculated to keep a rotating shaft from touching its bearing housing. A controlled layer of lubricant reduces friction, wear, and energy loss. It also helps the machine run smoothly by preventing metal-to-metal contact. The calculation starts with the shaft’s tangential velocity. First, the rotational speed is converted to angular velocity. Then that value is multiplied by the shaft radius. The result is the shaft’s linear speed at its surface...

key terms and concepts

Learn how capillary action moves liquid through narrow spaces using surface tension and adhesion, and see its role in plants, porous materials, and printing.

Capillary Action in Narrow Spaces | JoVE K12

JoVE Core Civil Engineering provides a foundational exploration of essential construction materials in civil engineering, focusing on bricks, stones, steel, wood, and concrete through easy-to-understand animated videos. This collection covers the properties, manufacturing processes, and practical applications of these materials. Additionally, the accompanied science-in-action videos demonstrate the research experiments performed in laboratories.

civil engineering

Capillary Action in Narrow Spaces

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