Water viscosity

Before talking about the properties of water, it is necessary to understand the very concept of "water". It is a clear liquid, which in most cases has neither a characteristic color nor a smell. When water passes into another aggregate state, it forms derivatives, which are called ice, snow (solid states) or vapor (gaseous state). It is believed that it covers more than 70% of the surface of the planet Earth - it's all kinds of seas and oceans, rivers, lakes, glaciers and other hydrological objects.

Water is a strong solvent, which in natural conditions contains many mineral salts and various gases. If we talk about its physical properties, we immediately pay attention to the fact that when the ice melts, its density increases, while for other substances a similar process occurs to the exact opposite.

The main feature of water is viscosity. Viscosity itself is the ability of a substance (be it liquid, gas or solid) to resist while moving particles of matter relative to each other. This characteristic can be of two types - volumetric and tangential. Volumetric viscosity is the ability of a substance to take a tensile force. It manifests itself when sound or ultrasonic waves propagate in water. Tangential viscosity is characterized by the ability of the fluid to withstand shear force.

When scientists investigated the viscosity of water, it was found that the resistance of the substance during stretching and shifts depends on the velocity of the particles of different layers of liquid. If a layer that moves faster affects a layer that moves slower, then an accelerating force is applied. If everything happens the other way around, then the braking force begins to act. The above forces are directed along the tangent to the surfaces of the layers.

According to Newton's law, the formula τ = μ dυ / dn was derived, according to which the internal friction force is proportional to the velocity gradient in the normal and in the area of the action. If we refer the force of friction to an area that is equal to unity, we obtain a shearing stress in the liquid, which is indicated in the above formula.

There is also such a thing as the kinematic viscosity of water. It denotes the ratio of the dynamic coefficient (μ) to the density of the selected fluid (ρ). As a formula, this expression will look like this: ν = μ / ρ.

The viscosity of water varies at different temperatures, that is, the values of its coefficients decrease with increasing temperature. Thus, the dynamic coefficient of viscosity of salt water will slightly differ from the coefficient of fresh water. When calculating the indicator itself, the difference will fluctuate around 5%.

We can give some more formulas, but this is of no use, since the main material was described earlier. The viscosity of water, by definition, can vary, not to mention the aggregate states of matter. These data are important in aircraft and shipbuilding and some other industries.

There is a special table for determining the viscosity of water under different temperature conditions. This material can be used not only in theory, but also in practice. In the table data are given with an interval of 5 degrees, ranging from 5 to 100 degrees, which greatly facilitates the life of teachers and students of universities when performing calculations.

Another important indicator - the dynamic kinematic viscosity of water, the so-called second viscosity (volumetric) - is a characteristic of volume compression deformation. It plays a significant role in the attenuation of sound and in the reduction of shock waves.