How to play irregular waves in a towing tank pool
(57) Abstract:The invention relates to experimental hydrodynamics and applies technologies of reproduction irregular waves in a towing tank pool with volnoproektorom. How to play irregular waves in the model tank is in the synthesis of harmonic components in a given energy spectrum of emotion. Harmonic components of the simulated disturbances set alternately in the generation of waves by the wave maker. These harmonic components are set randomly in time at a constant amplitude oscillations volnoobraznaya body. The technical result of the invention is to improve the quality of experiments in a towing tank basin, by obtaining irregular waves of long duration by simplifying the control circuit wavemaker, as well as in reducing the complexity of the experiment. 2 Il. The invention relates to the field of carrying out hydrodynamic tests with the help of technical means and refers to the problem of modeling of irregular waves in the model tank.A known method of generating irregular valentijnsdag unrest (see Annunciation S. N., The Holodilin A. N. Reference statics and dynamics of the ship. So 2, Leningrad: Sudostroenie, 1975, S. 140). The disadvantage of this method is the need for sophisticated equipment for amplitude fluctuations volnoobraznaya body mechanical wavemaker. In addition, due to the large inertia of the mechanical volnoproektorom, no playback irregular waves good quality.Also known how to play irregular waves, when the harmonic components are set sequentially in order of decreasing frequency; harmonic components are characterized by the amplitude and frequency of the wave (USSR Author's certificate, 1051399, G 01 M 10/00) is adopted for the prototype. However, this method has the following disadvantages:
the implementation process unrest turns out briefly that it is not possible to conduct tests on models of large size;
the excitement with the given parameters is obtained only at a certain point, which eliminates the trials of moving models;
it takes time to change the amplitude of oscillation volnoobraznaya body that does not allow him to use the mechanical volnoproektorom sectional type with handle is a great time.The objective of the invention is to improve the quality of experiments in a towing tank basin, by obtaining irregular waves of long duration by simplifying the control circuit wavemaker, as well as reducing the complexity of the experiment.To achieve the technical result in the famous case of reproduction of irregular waves in the model tank through a synthesis of harmonic components in a given energy spectrum of emotion, asked alternately generating waves wavemaker, harmonics are set randomly in time at a constant amplitude oscillations volnoobraznaya body. The random nature of the implementation is provided by the distribution of harmonic components in accordance with the law of equal probability.Job harmonic components of the simulated disturbances in random order provides
the possibility of obtaining the implementation of the excitement of long duration, which allows to carry out tests on models of large size;
the possibility of obtaining irregular waves with specified characteristics along the length of the working section of the basin that call Ustia necessary changes in the amplitude of the oscillations volnoobraznaya body during the generation of irregular waves.The essence of the method consists in the following. Ask the energy spectrum of the excitement and the duration of the process generating excitement T. Determine the energy spectrum of fluctuations volnoobraznaya body's taking into account the amplitude-frequency characteristics of the wavemaker. The simulated energy spectrum of fluctuations volnoobraznaya body is divided into n parts with an interval . The simulated process is divided into the same number of harmonic components having a certain frequency and duration.The duration of the wavemaker at a certain frequency is proportional to the spectral energy at the given frequency, which is determined by the formula
where Eithe energy corresponding to the frequencyi; Si- the value of the spectral density corresponding to the frequencyi; =i-i-1; i (1;n).The ratio of the length sections fixed frequency and energy at different frequencies looks as follows:
< / BR>this is subject to the following conditions:
= T - set the duration of the process,
= D is the variance of the process.Then components with frequenciesibody , constant during the whole time of generation of irregular waves is determined from the following equation:
= (2D)0.5.After that generate in the pool wave wavemaker.In the process of generating the amplitude generated by the wavemaker wave varies with frequency at constant amplitude oscillations volnoobraznaya body due to the fact that the amplitude-frequency characteristic (AFC) of the wavemaker is not constant depending on the frequency.In Fig. 1 shows the spectrum obtained by the proposed method unrest in Fig. 2 - frequency response of the wavemaker.From the curves of Fig. 1 and Fig. 2 shows that at constant amplitude oscillations volnoobraznaya body of the amplitude of the generated waves vary from small at low frequencies to large, medium and again small at high frequencies, which completely corresponds to the spectral theory of sea waves.If necessary, change the shape of the reproduced spectrum excitement produced by changing the duration of the harmonic components, and the change in height of the spectrum (dispersion process) is produced by changing the amplitude of the oscillations volnoobraznaya body, which yet get irregular excitement high quality wavemaker any type, to simplify the control circuit mechanical volnoproektorom irregular waves, to convert existing pornoproduktion regular waves for the generation of irregular waves without significant material cost, and improve reliability and quality nautical experiments on irregular waves. How to play irregular waves in the model tank through a synthesis of harmonic components in a given energy spectrum of emotion, asked alternately generating waves wavemaker, wherein harmonic components of the simulated disturbances set randomly in time at a constant amplitude oscillations volnoobraznaya body.
FIELD: experimental hydromechanics; designing of equipment for conducting hydrodynamic and ice searches of marine engineering facility models in model testing basins.
SUBSTANCE: proposed device includes towing trolley with frame rigidly secured on it; this frame is provided with bar which is connected with model through dynamometers and bearing plate. Dynamometers form three-support force-measuring system; they are provided in each support in form of two interconnected elastic members; one elastic member is made in form of five-rod member provided with longitudinal and lateral force sensors; it is located between two flanges. Second elastic member of dynamometer is made in form of membrane-type elastic member whose membrane is located between rigid rim and rigid central part of this member provided with threaded rod with elastic hinge mounted over vertical axis perpendicularly relative to membrane. Membrane, rim and rigid central part with threaded rod and elastic hinge are made integral. Rim of membrane elastic members is rigidly connected with one of flanges of five-rod elastic member in such way that threaded rod is located along vertical axis of support and is rigidly connected via elastic hinge with bearing plate secured on model. Membrane is provided with resistance strain gages forming vertical force measuring bridge. Second flange of each five-rod member is connected with additional bearing plate secured on bar.
EFFECT: enhanced accuracy of measuring forces and moments.