CN109238553B - Pressure distribution measuring method for columnar shock waves in water - Google Patents

Pressure distribution measuring method for columnar shock waves in water Download PDF

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CN109238553B
CN109238553B CN201811212878.6A CN201811212878A CN109238553B CN 109238553 B CN109238553 B CN 109238553B CN 201811212878 A CN201811212878 A CN 201811212878A CN 109238553 B CN109238553 B CN 109238553B
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shock waves
shock wave
light
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CN109238553A (en
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王静竹
王一伟
杜特专
黄荐
黄晨光
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Institute of Mechanics of CAS
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
    • G01L11/02—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by optical means

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Abstract

The invention discloses a pressure distribution measuring method for columnar shock waves in water, wherein the columnar shock waves are two-dimensional shock waves, and a first image set of light rays emitted by a light source passing through a speckle background and a two-dimensional water tank without the columnar shock waves is obtained by adopting a camera device; acquiring a second image set of the light emitted by the light source passing through a speckle background and the two-dimensional water tank loaded with the columnar shock waves by using a camera device; determining the offset of the background speckles at the columnar shock wave through comparison of the first image set and the second image set based on a first formula; determining the refractive index of the light through the offset of the speckles based on a second formula and a third formula; determining the density and the pressure of the columnar shock wave through the light ray refractive index based on a fourth formula and a fifth formula; the invention can not only obtain the pressure distribution of shock wave propagation in a small range, but also achieve the purpose of observing the shock wave propagation by using less optical equipment.

Description

Pressure distribution measuring method for columnar shock waves in water
Technical Field
The invention relates to the field of pressure distribution measurement, in particular to a pressure distribution measurement method for columnar shock waves in water.
Background
An underwater shock wave is a compression wave in which the pressure, density and temperature in a liquid medium change abruptly at the wave front.
The compressibility of water is relatively low, the pulse width value of shock waves in water is relatively narrow, and the propagation speed of the shock waves in water is more than or equal to 1500mm/s at normal temperature, so that a high-frequency-response and high-resolution pressure sensor is needed for measuring the shock waves in water.
Disclosure of Invention
The problem to be solved by the invention is to be able to measure the pressure distribution of the shock wave propagation in a small range and to observe the image of the shock wave propagation.
In order to solve the above problems, the present invention provides a method for measuring pressure distribution of columnar shock waves in water, the method comprising the steps of:
the method comprises the steps that a camera device is adopted to obtain a first image set of light rays emitted by a light source passing through a speckle background and a two-dimensional water tank without columnar shock waves;
acquiring a second image set of the light emitted by the light source passing through a speckle background and the two-dimensional water tank loaded with the columnar shock waves by using a camera device;
determining an offset of speckle at the columnar shockwave from a comparison of the first image set and the second image set based on a first formula;
determining the refractive index of the light through the offset of the speckles based on a second formula and a third formula;
and determining the density and the pressure of the columnar shock wave through the light ray refractive index based on a fourth formula and a fifth formula.
Further, the columnar shockwave is a two-dimensional columnar shockwave.
Further, the first formula is as follows:
Figure BDA0001832831550000021
further, Δ x and Δ y in the first formula are offsets of speckles in the horizontal and vertical directions, respectively, Δ t is a time interval between two continuous visual images recorded by the high-speed camera, and when calculating speckle displacement, Δ t takes a value of 1, and f is a valueijkIs the image brightness at the intersection of the ith row and the jth column in the kth image frame, (f)ijk)x，(fijk)y，(fijk) t is the partial derivative of the image intensity of x, y, t, respectively.
Further, the second formula is as follows:
Figure BDA0001832831550000022
the third formula is as follows:
Figure BDA0001832831550000023
further, Z in the second and third formulasDIs the distance from the speckle background to the center of the columnar shock wave, ZBIs the distance from the speckle background to the camera lens, and f is the focal distance of the lens.
Further, the fourth and fifth formulas are as follows:
the fifth formula is as follows:
further, in the fourth and fifth formulas, P is the pressure of the columnar shockwave, ρ is the density of the columnar shockwave, B is 2963bar, γ is 7.415, and P is0＝1.03bar。
The invention has the following beneficial effects: the invention relates to a pressure distribution measuring method for columnar shock waves in water, which is mainly used for measuring the pressure distribution of two-dimensional columnar shock waves, and the method comprises the steps of firstly, obtaining an image of a speckle background in the process of shifting the columnar shock waves through a camera device, and determining the offset of the speckle background based on a first formula; determining the refractive index of the light according to the offset of the speckle background, and further determining the density and the pressure of the columnar shock wave according to the refractive index of the light; the image processing method adopts a time-space method in an optical flow method, compared with a particle image processing method in a PIV, the method can more accurately process the speckle deviation of less than one pixel caused by the shock wave in water, and on the other hand, the pressure distribution measuring method in the invention can achieve the purpose of observing the propagation of the shock wave by using less optical equipment.
Drawings
Fig. 1 is a flow chart of a method for measuring pressure distribution of columnar shock waves in water according to an embodiment of the present invention;
Detailed Description
In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, a technical method in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without any creative effort, shall fall within the protection scope of the present invention.
The experimental equipment mainly used in this embodiment includes: a light source, a speckle background, and a high-speed camera.
Fig. 1 is a flowchart of a method for measuring pressure distribution of columnar shockwaves in water according to an embodiment of the present invention, where the method specifically includes:
s101, acquiring a first image set of light rays emitted by a light source passing through a speckle background and a two-dimensional water tank without columnar shock waves by using a camera device;
the high-speed camera acquires an image of light emitted by the light source when the light passes through a two-dimensional water tank without a speckle background or columnar shock waves.
S102, acquiring a second image set of the light emitted by the light source, which passes through a speckle background and a two-dimensional water tank loaded with columnar shock waves, by using a camera device;
there are various methods for generating the shock wave, such as laser, underwater explosion, underwater discharge, etc., and in the present embodiment, the experiment was performed using the shock wave generated by the underwater discharge.
Firstly, after the two-dimensional water tank generates the shock wave, the light is refracted when passing through the columnar shock wave due to the density change of the columnar shock wave in the two-dimensional water tank, so that the speckle is deviated.
At this time, the high-speed camera acquires an image of the two-dimensional water tank, in which light emitted from the light source passes through a speckle background to generate columnar shock waves.
S103, determining the offset of the speckles at the columnar shock wave position through comparison of the first image set and the second image set based on a first formula;
according to the first formula, the images in S101 and S102 are processed and calculated, and the offset of the speckle at the columnar shock wave can be obtained.
Wherein the first formula is as follows:
Figure BDA0001832831550000041
in the first formula, deltax and deltay are speckle displacement in the horizontal and vertical directions respectively, deltat is the time interval of two continuous visual images acquired by a high-speed camera, and when the offset of speckles is calculated, the value of deltat is 1, f isijkIs the image brightness at the intersection of the ith row and the jth column in the kth image frame, (f)ijk)x，(fijk)y，(fijk) t is the partial derivative of the image intensity of x, y, t, respectively.
S105, determining the refractive index of the light through the offset of the speckles based on a second formula and a third formula;
wherein the second formula is as follows:
Figure BDA0001832831550000051
the third formula is as follows:
Figure BDA0001832831550000052
z in the second and third formulasDIs the distance from the speckle background to the center of the columnar shock wave, ZBF is the distance from the speckle background to the lens of the high-speed camera, and f is the focal distance of the lens of the high-speed camera.
S106, determining the density and the pressure of the columnar shock wave through the light ray refractive index based on a fourth formula and a fifth formula;
wherein the fourth formula is as follows:
Figure BDA0001832831550000053
the fifth formula is as follows:
Figure BDA0001832831550000054
the fourth and fifth formulas are shown in the following formulas, where P is the pressure of the columnar shock wave, ρ is the density of the columnar shock wave, B is 2963bar, γ is 7.415, and P is0＝1.03bar。
The columnar shock wave in the invention is a two-dimensional columnar shock wave.
The speckle background in the invention not only includes the background with regular and irregular spots, but also includes other types of backgrounds, such as a lattice shape, a stripe shape, etc.

Claims (3)

1. A pressure distribution measuring method for columnar shock waves in water is characterized by comprising the following steps:
the method comprises the steps that a camera device is adopted to obtain a first image set of light rays emitted by a light source passing through a speckle background and a two-dimensional water tank without columnar shock waves;
acquiring a second image set of the light emitted by the light source passing through a speckle background and the two-dimensional water tank loaded with the columnar shock waves by using a camera device;
determining an offset of speckle at the columnar shockwave from a comparison of the first image set and the second image set based on a first formula;
determining the refractive index of the light through the offset of the speckles based on a second formula and a third formula;
determining the density and the pressure of the columnar shock wave through the light ray refractive index based on a fourth formula and a fifth formula;
the first formula is as follows:
Figure FDA0002299124670000011
Δ x and Δ y in the first formula are offsets of the speckles in the horizontal and vertical directions, respectively, Δ t is a time interval between two continuous visual images, fijkIs the firstThe image brightness at the intersection of the ith row and the jth column in the k image frame, (f)ijk)x，(fijk)y，(fijk) t is the partial derivative of the image brightness corresponding to x, y and t respectively;
the second formula
The following were used:
Figure FDA0002299124670000012
the third formula is as follows:
Figure FDA0002299124670000021
z in the second and third formulasDIs the distance, Z, from the speckle background to the center of the columnar shock waveBThe distance from the speckle background to a lens of the image pickup device is defined as f, and the focal distance of the lens of the image pickup device is defined as f;
the fourth formula is as follows:
Figure FDA0002299124670000022
the fifth formula is as follows:
Figure FDA0002299124670000023
in the fourth formula and the fifth formula, P is the pressure of the columnar shock wave and is the columnar shock wave density, B is 2963bar, γ is 7.415, and P is0＝1.03bar。
2. The method of claim 1, wherein the columnar shockwave is a two-dimensional shockwave.
3. The method of claim 1, wherein the speckle background comprises at least one of:
regular spots, irregular spots, lattice shapes, and stripe shapes.
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CN86203799U (en) * 1986-06-11 1987-10-03 北京光电技术研究所 Portable laser dynamic hologram-speckle camera
JP2010236911A (en) * 2009-03-30 2010-10-21 Kyoto Institute Of Technology Method of analyzing molecule by utilizing laser-induced plasma shockwave
CN103123286A (en) * 2012-11-28 2013-05-29 江苏大学 Detection method and device for laser shock wave space-time distribution characteristic
CN103424221A (en) * 2013-03-27 2013-12-04 常州大学 Method and device for measuring explosion shock wave energy of combustible gas

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US6756579B2 (en) * 2002-03-27 2004-06-29 The United States Of America As Represented By The Secretary Of The Navy Optical fiber based apparatus and sensor with enhanced signal for pressure measurements
CN102494830A (en) * 2011-12-31 2012-06-13 北京理工大学 Method for measuring explosion shock wave field strength and special-purpose pressure tank thereof
CN103292943A (en) * 2012-02-27 2013-09-11 中国人民解放军总参谋部工程兵科研三所 Non-contact type impact wave hyperpressure measuring method
CN106706197B (en) * 2016-11-16 2019-03-05 哈尔滨工程大学 Measure of Underwater Explosion Pressure device based on improved Hopkinson bar
CN108519401B (en) * 2018-03-27 2021-03-02 北京航空航天大学 Test device for inhibiting speckle image shaking in 1200 ℃ aerobic high-temperature environment
CN108444353B (en) * 2018-04-19 2023-11-28 宁波交通工程建设集团有限公司 Tunnel excavation blasting shock wave protection device and operation method

Patent Citations (4)

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Publication number Priority date Publication date Assignee Title
CN86203799U (en) * 1986-06-11 1987-10-03 北京光电技术研究所 Portable laser dynamic hologram-speckle camera
JP2010236911A (en) * 2009-03-30 2010-10-21 Kyoto Institute Of Technology Method of analyzing molecule by utilizing laser-induced plasma shockwave
CN103123286A (en) * 2012-11-28 2013-05-29 江苏大学 Detection method and device for laser shock wave space-time distribution characteristic
CN103424221A (en) * 2013-03-27 2013-12-04 常州大学 Method and device for measuring explosion shock wave energy of combustible gas

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