Method for modeling one-dimensional harmonic acoustic fields in extensive narrow closed hydro-chamber

FIELD: hydro-acoustics, possible use for calibration of linear receiving hydro-acoustic measuring antennas in laboratory conditions.

SUBSTANCE: method for modeling one-dimensional harmonic acoustic fields in extensive narrow closed hydro-chamber includes placing hydro-acoustic emitters in it so that maximal distance between any adjacent emitters does not exceed half of wave length of harmonic field being modeled, and amplitudes of acoustic pressure, created by emitters, satisfy certain ratios.

EFFECT: simplified modeling process.

1 dwg

 

The invention relates to the field of hydro-acoustics and can be used for calibration and calibration foster linear acoustic antennas (LGA) credit guarantees under laboratory conditions.

There is a method similar purpose, which consists in the arrangement in long, narrow closed hydroxamate (PUSH) reference hydrophones and sonar emitters excited by electrical signals [U.S. Patent No. 4468760, CL 367-13, (H 04 R 29/00), 1984].

In this analogue in PUSH using sonar emitters simulated plane wave incident at an angle to test LGA. Measuring the parameters of the output signal of LGA when changing the angle of incidence determines the directional characteristic and the sensitivity of LGA.

The disadvantage of this method is the difficulty of determining the values of the signals applied to the emitters arising from the need for prior measurements.

There is a method of modeling of planar acoustic waves the one-dimensional acoustic fields in PUSH, consisting of equidistant location in hydroxamate N hydroacoustic radiators and exposed to electric signals [RF Patent №2116705, CL H 04 R 29/00, 1998], adopted for the prototype.

Hydroacoustic radiators in PUSH in the prototype feature so that the maximum distance IU is do any adjacent emitters do not exceed π /kmaxwhere kmax- the maximum wave number of the simulated acoustic field and affecting the emitters electrical signals satisfy the mathematical value

where- vector with elements

where unelectric signal supplied to the n-th emitter, a Enhis sensitivity to radiationmatrix inverse to the matrixwith;- the radius vector of the point where the m-th emitter,solution of the wave equation for the desired volume when it has only the n-th emitter,- vector with elements,function of the pressure distribution in the simulated acoustic field.

For the case of simulations PUSH harmonic acoustic field

where Rmthe pressure of the simulated harmonic acoustic field at a location m-th emitter, R0the amplitude of the acoustic pressure of the simulated field, k0is the wave number of the simulated fields, xm- food the other coordinate of the point of location of the m-th emitter, θ - the angle of incidence of the simulated wave on the axis PUSH.

While the elements of the matrixhave the following form

where L is the length of PUSH, k is the wave number of the acoustic field in PUSH, x is the longitudinal coordinate, xn- coordinate locations of the n-th emitter.

The disadvantage of the prototype is the need for a large number of calculations for modeling one-dimensional harmonic acoustic fields: the first step is to calculate the matrix elementsthe number of which is equal to N2after which carry out complex matrix calculations to determine the elements of the inverse matrixwhich quantity is also equal to N2.

The technical result from implementation of the invention is to eliminate the disadvantage of the prototype, i.e. reducing the number of calculations for modeling one-dimensional harmonic acoustic field.

This technical result is achieved due to the fact that in the known method modeling of acoustic fields in PUSH, consisting of equidistant location in hydroxamate N hydroacoustic radiators and exposed to electric signals, sonar emitters in hydroxamate are thus the om, to the distance between the emitters does not exceed half the wavelength of the simulated harmonic acoustic field, and the amplitude of the acoustic pressure generated by the emitters, satisfied mathematical value

where pm, m=0,..., N-1 acoustic pressure generated by the m-m emitter, θ - the angle of incidence of the simulated field, e is the number of "e", i - imaginary unit, k0is the wave number of the simulated acoustic field, d is the distance between emitters, k is the wave number of the acoustic field in hydroxamate, x0- zero coordinate of the emitter, L is the length of hydrochory.

The essence of the method consists in the following. For simplicity of calculations, the dependence on angle of incidence below will be omitted in the expressions pmand A. the Original matrix equation (1) for the case of modeling one-dimensional harmonic field at m=0 is written in the following form

Substituting into this equation the expression for F0,nget the

Similarly, from equation (1) when m=N-1 we have

From equation (1) when m=7, having done the necessary Mat is automatic calculations taking into account (7) and (8), get the

From equation (1) when m=N-2, performing the necessary mathematical calculations taking into account (7) and (8), we obtain

Consideration of equation (3) for arbitrary values of m allows to obtain recurrent expression for pm, m=1, ..., N-2.

This requires consideration of a large number of mathematical calculations, which are omitted here and below, as a non-fundamental for the disclosure of beings of the proposed method.

From the last expression we obtain for m=1

In addition, the resulting expression (11) allows from recurrent expressions to go to a direct expression for pm

Thus, the resulting expression(9), (12), (13) and (10) are expressions for pm, m=0, ..., N-1 in analytical form, represented in the mathematical equation (5).

The distance between the emitters in this case is given by the expression

where λ is the wavelength of the acoustic field in PUSH.

The invention is illustrated by the drawing, which shows a diagram of PUSH. Along hydrochory 1 length L equidistant with step d are N emitters 2. In gidrotamir put LGA 3. The master oscillator generates e is tricocci signal frequency f, served on N generators signal. This signal determines the frequency of the output of the harmonic signals all signal generators. Then is determined by the amplitude of the P0and the angle of incidence θ simulated harmonic fields. By the formulas (5) compute the complex amplitude of the acoustic pressure pm, m=0,..., N-1, which should create the emitters. By the formula (2) compute the complex amplitude of the electric signals, which should be submitted to the emitters, i.e. the amplitude of the output signals of the generators. Thus it is necessary to measure the speed of sound in PUSH with and sensitivity of the emitters Em, m=0,..., N-1.

After establishing in hydroxamate simulated acoustic field is measured by the output signal of LGA, which defines its parameters.

A method for simulating the one-dimensional harmonic acoustic field in a long, narrow closed hydroxamate, consisting of equidistant location in hydroxamate N hydroacoustic radiators and exposed to an electric signal, characterized in that the sonar emitters in hydroxamate feature so that the distance between the emitters does not exceed half the wavelength of the simulated acoustic field, and the amplitude of the acoustic pressure generated by the emitters, meet varali mathematical value

where pm, m=0,..., N-1 acoustic pressure generated by the m-m emitter, θ - the angle of incidence of the simulated field, e is the number of "e", i - imaginary unit, k0is the wave number of the simulated acoustic field, d is the distance between emitters, k is the wave number of the acoustic field in hydroxamate, x0- zero coordinate of the emitter, L is the length of hydrochory.



 

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