The theory of sonics is a branch of continuum mechanics which describes the transmission of mechanical energy through vibrations. The birth of the theory of sonics is the publication of the book A treatise on transmission of power by vibrations in 1918 by the Romanian scientist Gogu Constantinescu. "ONE of the fundamental problems of mechanical engineering is that of transmitting energy found in nature, after suitable transformation, to some point at which can be made available for performing useful work. The methods of transmitting power known and practised by engineers are broadly included in two classes: mechanical including hydraulic, pneumatic and wire rope methods; and electrical methods....According to the new system, energy is transmitted from one point to another, which may be at a considerable distance, by means of impressed variations of pressure or tension producing longitudinal vibrations in solid, liquid or gaseous columns. The energy is transmitted by periodic changes of pressure and volume in the longitudinal direction and may be described as wave transmission of power, or mechanical wave transmission. – Gogu Constantinescu" Later on the theory was expanded in electro-sonic, hydro-sonic, sonostereo-sonic and thermo-sonic. The theory was the first chapter of compressible flow applications and has stated for the first time the mathematical theory of compressible fluid, and was considered a branch of continuum mechanics. The laws discovered by Constantinescu, used in sonicity are the same with the laws used in electricity.

Book chapters

The book A treatise on transmission of power by vibrations has the following chapters: George Constantinescu defined his work as follow.

Theory of sonics: applications

Elementary physical principles

If v is the velocity of which wa****ves tra****vel along the pipe, a****nd n the number of the revolutions of the cra****nk a, then the wa****velength λ is: Assuming that the pipe is finite and closed at the point r situated at a distance which is multiple of λ, and considering that the piston is smaller than wavelength, at r the wave compression is stopped and reflected, the reflected wave traveling back along the pipe.

Definitions

Alternating fluid currents

Considering any flow or pipes, if: and then we have: Assuming that the fluid current is produced by a piston having a simple harmonic movement, in a piston cylinder having a section of Ω square centimeters. If we have: Then: Where: If T= period of a complete alternation (one revolution of the crank) then: The effective current can be defined by the equation: The stroke volume δ will be given by the relation:

Alternating pressures

The alternating pressures are very similar to alternating currents in electricity. In a pipe where the currents are flowing, we will have: Considering the above formulas: If p1 is the pressure at an arbitrary point and p2 pressure in another arbitrary point: The effective hydromotive force will be:

Friction

In alternating current flowing through a pipe, there is friction at the surface of the pipe and also in the liquid itself. Therefore, the relation between the hydromotive force and current can be written as: Using experiments R may be calculated from formula: Where: If we introduce \epsilon in the formula, we get: For pipes with a greater diameter, a greater velocity can be achieved for same value of k. The loss of power due to friction is calculated by:

Capacity and condensers

Definition: Hydraulic condensers are appliances for making alterations in value of fluid currents, pressures or phases of alternating fluid currents. The apparatus usually consists of a mobile solid body, which divides the liquid column, and is fixed elastically in a middle position such that it follows the movements of the liquid column. The principal function of hydraulic condensers is to counteract inertia effects due to moving masses.