THEMES

Capillary hydrostatic pressure

Capillary hydrostatic pressure

The hydrostatic pressure is related to what we know as thrust of Archimedes, we will see how and why. To understand what it is, just think of a fluid at rest and the force it exerts on the surface unit with which it is normally in contact. On a glass, on our body, on a dam, on a glass… how many examples of hydrostatic pressure!

This size depends only on the density of the fluid and the sinking of the point considered by the free hair, does not vary with the mass below the point considered. He showed it to us Pascal when he put water in a perforated container and pushed it down: it comes out with the same intensity and speed.

Hydrostatic pressure: formula

Her formula is :

p = ρgh

where p is the static pressure (Pa), ρ (rho) is the density of the fluid (Kg / m3), g is the acceleration of gravity and h is the height of the point considered (m).

Capillary hydrostatic pressure

There are scientists like Starling who sought to describe the role of hydrostatic and oncotic force in the movement of fluids through capillary membranes. It seems a very technical thing, but in truth it can also impact on daily life.

In particular, Starling focused on an equation describing the movement of fluid by filtration through the membrane of the capillaries and which is determined by the hydrostatic pressure opposed by the osmotic pressure. When the hydrostatic pressure exceeds the oncotic pressure, the liquid passes from the capillaries into the interstitial spaces.

Hydrostatic pressure: blood

In the blood there is the oncotic pressure, or the pressure produced in a solution by large molecules, proteins, which all remain in the vessels and have the ability to hold water inside the vessels. The blood carries in reverse a pressure on the surface of the capillaries called hydrostatic pressure.

Hydrostatic pressure and buoyancy

Including what the hydrostatic pressure, let's move on to the hydrostatic thrust that perhaps many of us call Archimedes thrust, deriving from the Archimedes principle. It states that "A body immersed in a fluid receives a thrust from the bottom upwards equal to the weight of the volume of fluid moved"

Hydrostatic pressure: exercises

There are many practical examples and different exercises that help us become familiar with the hydrostatic pressure and with its consequences, theoretical and practical, often to be considered with the atmospheric pressure. One of the situations often proposed in the exercises is that of communicating vessels, containers connected to each other containing the same liquid at rest, with the same free surface level, regardless of the shape of the containers.

In other exercises the problem of calculating the hydrostatic pressure if there are two or more non-miscible fluids with different densities: it is the sum of the pressures caused by the different fluids.

Hydrostatic pressure and 3D printing

One is based on the hydrostatic pressure innovative printing technique that revolutionizes the craft sector and beyond. Is called cubicatura, or even Water Transfert Printing, is a 3D effect coating technique that can transfer any image from a film onto an object exploiting the hydrostatic pressure to adhere to the surface without imperfections.

It's about a actual painting, has nothing to do with the application of a film, also because the cubication works on many types of surfaces: if an object can be immersed in water, the hydrographic process can be used. This means being able to decorate plastic, wood, fiberglass, ceramics, metals and alloys overcoming the problems that occurred with traditional methods such as hot stamping, transfer printing and the like others.

In the automotive industry, cubication can be used customize motorcycle bodywork and helmet, car finishes such as dashboards, gear knobs and steering wheels. In other fields the same technique allows to intervene on shells of mobile phones, computers and furnishing accessories such as household appliances but also vases and furnishings of all kinds. The certainty is that this method it does not alter the properties of the treated objects or even their individual components.

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