CN113155338B - System and method for testing time constant of underwater explosion near-field shock wave - Google Patents
System and method for testing time constant of underwater explosion near-field shock wave Download PDFInfo
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Abstract
The invention discloses a time constant testing system and a time constant testing method for an underwater explosion near-field shock wave.A PVDF sensor group comprising a plurality of PVDF sensors is adopted to replace a single sensor, and the plurality of PVDF sensors are arranged in a non-linear staggered manner, so that under the condition of more complex near-field conditions, the mutual interference among the sensors is weakened, and the accuracy of the testing system is improved; the PVDF sensor group is assembled on the assembly plate, so that the water inlet process of the sensor group and the explosive is simplified; the suspension placement of the sensors and the explosive is avoided, the connection supporting structure between the sensors is arranged, the position of the test point can be controlled accurately, the transverse stretching effect caused by the bending deformation of the sensors along with the structure is reduced, and the test accuracy is improved. By the underwater explosion near-field bubble and shock wave combined test method, the time constant of the underwater explosion near-field shock wave is finally tested.
Description
Technical Field
The invention belongs to the technical field of underwater explosion tests, and particularly relates to a system and a method for testing a time constant of an underwater explosion near-field shock wave.
Background
In the initial stage of underwater explosion of the explosive, the energy of the explosive is mainly transmitted outwards in the form of shock waves, and the energy is decisive for the damage of the target. In the prior art, the research on underwater explosion is mainly focused in the area which is 10 times of the charging radius, the pressure peak value is generally not more than 200MPa, and the research on the near field in the underwater explosion which is 1-10 times of the charging radius is not sufficient. The near-field shock wave pressure has the characteristics of high peak value and high change speed, so that the development of test research on the time constant of the underwater explosion near-field shock wave is of great significance in researching the near-field propagation characteristic of the underwater explosion shock wave.
The sensors for testing the explosion pressure at present mainly comprise a PCB series pressure sensor, a manganin piezoresistive gauge and a polyvinylidene fluoride (PVDF) sensor, and the PCB series pressure sensor is often adopted for testing the internal shock wave pressure of the underwater fluid in the prior art. Due to the complex state of the near-field fluid medium and the rapid attenuation of the shock wave pressure, the test signal can be interfered in many aspects, and the PCB series pressure sensor is not easy to install, thereby causing inevitable test errors. In summary, the time decay constant of the near-field shockwave obtained by the prior art only using the pressure test is inaccurate.
Disclosure of Invention
In view of this, the invention provides a system and a method for testing the time constant of an underwater explosion near-field shock wave, which can support the joint test of bubbles and shock waves of the underwater explosion near-field and realize the test of the time constant of the underwater explosion near-field shock wave.
The invention provides a time constant test system for an underwater explosion near-field shock wave, which comprises: the device comprises a water tank, an assembling plate, a connecting plate, a supporting and positioning net rack, a PVDF sensor group, a signal conditioning instrument, a high-frequency data acquisition instrument, an upper computer, explosive to be detected, a first high-speed camera, a second high-speed camera, a detonator and a synchronous trigger device;
wherein, two transparent pressure-resistant observation windows are symmetrically arranged on the side wall of the water tank;
the supporting and positioning net rack is used for limiting the initial position of the explosive to be tested at the geometric center of the water tank, and the supporting and positioning net rack is fixed in the middle of the top opening of the water tank; the connecting plate is limited by a groove arranged in the middle of the supporting and positioning net rack and is fixedly connected with the supporting and positioning net rack;
the assembling plate is used for fixing the explosive to be tested and the PVDF sensor group, one end of the assembling plate is fixedly connected with the connecting plate, and the center of the other end of the assembling plate is provided with a through hole A; the detonator assembling rod is of a hollow structure, one end of the detonator assembling rod is fixedly connected with the assembling plate through a through hole, the center of the other end of the detonator assembling rod is provided with a groove, the detonator is fixed in the groove of the detonator assembling rod, and a detonator wire of the detonator penetrates through the detonator assembling rod and the through hole A and extends out of the water tank; the explosive to be tested is fixed on the detonator; the detonator is connected with the synchronous trigger device, and the synchronous trigger device is connected with the upper computer;
a plurality of through square holes which are not linearly staggered are formed in the assembly plate around the through hole A, and the first end of the sensor assembly plate is matched with the through holes to fix the sensor assembly plate on the same side of the assembly plate; sensors in the PVDF sensor group are respectively fixed on one side, facing the through hole A, of the second end of the sensor assembling plate; the PVDF sensor group is sequentially connected with the signal conditioning instrument, the high-frequency data acquisition instrument and the upper computer;
the first high-speed camera and the second high-speed camera are both arranged in front of the same observation window of the water tank, and the shooting center positions of the first high-speed camera and the second high-speed camera and the center of the explosive to be detected are positioned on the same height horizontal plane; the second high-speed camera is placed between the first high-speed camera and the water tank; the first high-speed camera and the second high-speed camera are respectively connected with the synchronous trigger device and the upper computer.
Furthermore, the observation window is made of a transparent acrylic material plate, and the thickness of the observation window is set according to the explosion intensity of the explosive to be detected.
Further, the thickness of the observation window is 20 mm-30 mm.
Furthermore, the observation window is made of multiple layers of explosion-proof glass.
Furthermore, a fixing plate is sleeved on the sensor assembling plate.
The invention provides a method for testing a time constant of an underwater explosion near-field shock wave, which comprises the following steps:
Further, the process of processing the shooting result by the upper computer in the step 7 to obtain the time constant of the near-field shock wave of the explosive to be detected includes the following steps:
and 7.1, recording the time from the initiation to the bubble radius R as t according to the bubble form shot by the second high-speed camera0The boundary pressure P of the bubble at this time is calculated by the following formulab：
Wherein Q isvThe unit of the explosion heat of the explosive to be detected is J/g; w is the explosive loading quantity of the explosive to be detected, and the unit is g; r is the bubble radius, and the unit is m;
7.2, obtaining the shock wave peak pressure P of the position of each sensor according to the PVDF sensor groupmjJ is the serial number of the sensor, and the shock wave pressure test result of the explosive to be tested is obtained;
and 7.3, obtaining a track of the distance x between the shock wave front and the explosive along with the change of time according to the shooting result of the first high-speed camera, and carrying out nonlinear fitting on an x-t curve by using the following formula:
wherein A isi、BiAre all fitting coefficients, AiReflecting the intensity of the shock wave, BiReflecting the length of the decay time of the shock wave, c0Representing the sound velocity in water, wherein D is the detonation velocity of the explosive to be detected;
fitting to obtain coefficient Ai、BiAnd differentiating to obtain the shock wave velocity, and calculating by adopting the following formula to obtain the shock wave peak pressure P at the center r of the explosive (9) to be testedmr：
Pmr＝ρ0usup
Where ρ is0Density of water in g/cm 3; u. ofsIs the shock wave velocity, and the unit is km/s; u. ofpThe unit is km/s of the velocity of flow field particles after the shock wave, so that a change curve of the pressure peak value of the shock wave of the explosion near field along with the propagation distance is obtained;
step 7.4, setting the time t when the radius R of the bubble reaches the position of the jth sensoroLet P (t) be Pb，t＝t0，Pm＝PmjThen, the time constant of the jth sensor test point position can be obtained as θ:
further, the time constant in step 7.4 is calculated as follows:
let the time taken be t when the radius of the bubble is RoBoundary pressure of air bubble is PbIn the variation curve of the near-field shock wave pressure peak value along with the propagation distance obtained by processing the shock wave track test result, when the explosive center distance R is equal to the bubble radius R, the shock wave peak value pressure is PmrAnd obtaining the time constant theta according to the r position of the center of the explosive:
has the advantages that:
1. according to the invention, a PVDF sensor group comprising a plurality of PVDF sensors is adopted to replace a single sensor, and the plurality of PVDF sensors are arranged in a nonlinear staggered manner, so that under the condition of more complex near field conditions, the mutual interference among the sensors is weakened, and the accuracy of the test system is improved; the PVDF sensor group is assembled on the assembly plate, so that the water inlet process of the sensor group and the explosive is simplified; the suspension placement of the sensors and the explosive is avoided, the connection supporting structure between the sensors is arranged, the position of the test point can be controlled accurately, the transverse stretching effect caused by the bending deformation of the sensors along with the structure is reduced, and the test accuracy is improved.
2. The method adopts a combined test method of the air bubbles and the shock waves, adopts a high-speed camera to measure the explosion air bubbles, adopts a PVDF sensor group to measure the pressure of the shock waves, and combines an empirical formula to calculate and obtain the time constant of the underwater explosion near-field shock waves.
Drawings
FIG. 1 is a frame diagram of a system for testing the time constant of an underwater explosion near-field shock wave provided by the invention.
Fig. 2 is a schematic diagram of a time constant testing system for an underwater explosion near-field shock wave provided by the invention.
Fig. 3 is a schematic structural diagram of an assembly plate in the underwater explosion near-field shock wave time constant test system provided by the invention.
The device comprises a water tank 1, an assembly plate 2, a connecting plate 3, a supporting and positioning net rack 4, a PVDF sensor group 5, a signal conditioning instrument 6, a high-frequency data acquisition instrument 7, an upper computer 8, an explosive to be tested 9, a first high-speed camera 10, a second high-speed camera 11, a detonator 12 and a synchronous trigger 13.
Detailed Description
The invention is described in detail below by way of example with reference to the accompanying drawings.
The invention provides a test system for time constant of underwater explosion near-field shock wave, the system frame is shown in figure 1, the structure of the test system for time constant of underwater explosion near-field shock wave is shown in figure 2, and the test system comprises: the device comprises a water tank 1, an assembling plate 2, a connecting plate 3, a supporting and positioning net rack 4, a PVDF sensor group 5, a signal conditioning instrument 6, a high-frequency data acquisition instrument 7, an upper computer 8, explosive to be detected 9, a first high-speed camera 10, a second high-speed camera 11, a detonator 12 and a synchronous trigger device 13.
The water tank 1 is used for providing a test space for underwater explosion of the explosive to be tested. The water tank 1 is a cylinder with an opening at the top, two transparent pressure-resistant observation windows are symmetrically arranged on the side wall of the water tank 1, and a light channel formed by the two observation windows is convenient for the first high-speed camera 10 and the first high-speed camera 11 to more clearly shoot bubbles generated by explosive explosion. Wherein, in order to facilitate observation and taking a picture, the observation window is usually made of a transparent acrylic material plate, and meanwhile, the thickness of the observation window is different according to the different explosives to be tested, and the observation window is generally set to be 20-30 mm thick. In addition, the observation window can also be made of multiple layers of explosion-proof glass. Furthermore, in order to facilitate the control of the water injection depth in the test process, water level scale lines can be marked on the observation window.
And a positioning net rack 4 is supported and used for limiting the initial position of the explosive to be tested 9 to the geometric center of the water tank 1. The supporting and positioning net rack 4 is fixed in the middle of the top opening of the water tank 1; the connecting plate 3 is fixedly connected with the supporting and positioning net rack 4 through a groove arranged in the middle of the supporting and positioning net rack 4.
And the assembling plate 2 is used for fixing the explosive to be measured 9 and the PVDF sensor group 5. One end of the fitting plate 2 is fixedly connected to the connecting plate 3, for example, by bolts. The center of the other end of the assembling plate 2 is provided with a through hole; the detonator assembly rod is of a hollow structure, one end of the detonator assembly rod is fixedly connected with the assembly plate 2 through a through hole, the center of the other end of the detonator assembly rod is provided with a groove, a detonator 12 is fixed in the groove, and a detonator wire penetrates through the detonator assembly rod and the through hole and extends out of the water tank; set up a plurality of non-linear staggered's the square hole that link up around the through-hole, the cooperation through the first end of sensor assembly plate and perforating hole realizes sensor assembly plate and assembly plate 2 fixed, and further the sticky mode of accessible strengthens sensor assembly plate and assembly plate 2 stability, in addition, further strengthens the stability of sensor assembly plate through cup jointing the fixed plate on the sensor assembly plate. The explosive 9 to be tested is fixedly arranged on the detonator 12, and the explosive 9 to be tested is subjected to waterproof treatment. The detonator 12 is connected with the synchronous trigger device 13 through a detonating cord, and the synchronous trigger device 13 is connected with the upper computer 8.
And the PVDF sensor group 5 is used for measuring the shock wave pressure generated when the explosive 9 to be measured explodes. The PVDF sensor group 5 comprises a plurality of underwater pressure sensors, the underwater pressure sensors are respectively fixed on one side, facing the through hole, of the second end of the sensor assembling plate, one side of a sensitive element of each underwater pressure sensor and the explosive 9 to be tested are in the same plane, one side of a welding spot, connected with a cable, of each underwater pressure sensor faces a through square hole, and waterproof treatment is carried out on the welding spot, connected with the cable, of the PVDF sensor group 5. The PVDF sensor group 5 is sequentially connected with a signal conditioning instrument 6, a high-frequency data acquisition instrument 7 and an upper computer 8 to acquire test point data.
The first high-speed camera 10 is used for shooting bubble tracks of bubbles generated when the explosive to be measured explodes, and the second high-speed camera 11 is used for shooting bubble forms of the bubbles generated when the explosive to be measured explodes. The first high-speed camera 10 and the second high-speed camera 11 are both arranged in front of an observation window of the water tank 1, and the shooting center positions of the first high-speed camera 10 and the second high-speed camera 11 and the center of the explosive 9 to be tested are positioned on the same height horizontal plane. The second high-speed camera 11 is placed at a position between the first high-speed camera 10 and the water tank 1. The first high-speed camera 10 and the second high-speed camera 11 are respectively connected with the synchronous trigger device 13 and the upper computer 8.
The upper computer 8 is used for processing the received signals from the PVDF sensor group 5, the first high-speed camera 10 and the second high-speed camera 11 to obtain the time constant of the underwater explosion near-field shock wave of the explosive to be detected 9.
The invention provides a test method for time constants of underwater explosion near-field shock waves, which adopts the test system for the time constants of the underwater explosion near-field shock waves, and specifically comprises the following steps:
The length of a shooting view field of the first high-speed camera 10 is not less than 6 times of the charging radius of the explosive 9 to be detected, and the sampling frequency is not less than 200000 frames/second. The length of a shooting view field of the second high-speed camera 11 is not less than the maximum diameter of the bubble pulsation calculated by an empirical formula according to the explosive loading quantity of the explosive to be measured 9, and the sampling frequency is within the range of 10000 frames/second and 30000 frames/second.
And 3, fixing the PVDF sensor group 5 on the assembly plate 2. And (3) pasting the PVDF sensor group 5 at the second end of the sensor assembling plate, then inserting the sensor assembling plate into the through square hole on the assembling plate 2, enabling one side of the sensitive element to face to the position of the explosive to be detected 9, and carrying out waterproof treatment on the PVDF sensor group 5 and a welding spot connected with a cable. The PVDF sensor group 5, the signal conditioning instrument 6, the high-frequency data acquisition instrument 7 and the upper computer 8 are sequentially arranged to acquire test point data.
And 5, putting the assembled body of the connecting plate 3 and the assembling plate 2 which are installed into water, and assembling the assembled body at the central position of the supporting and positioning net rack 4.
And 6, confirming the state of the synchronous trigger device 13 and connecting the detonator line with the detonating cord.
The process of processing the test result by the upper computer 8 comprises the following steps:
and 7.1, calculating the boundary pressure of the air bubble according to the air bubble form shot by the second high-speed camera 11.
The time from the initiation of the detonation to the bubble radius R is denoted as t according to the bubble form captured by the second high-speed camera 110This is the first time the radius of the bubble reaches R during the bubble expansion phase, at which time the boundary pressure P of the bubble is calculated using the following formulab：
Wherein Q isvThe unit is J/g of the explosion heat of the explosive 9 to be detected; w is the explosive loading quantity of the explosive 9 to be detected, and the unit is g; r is the bubble radius in m.
7.2, according to the shock wave peak pressure P of the position where each sensor is uploaded by the PVDF sensor group 5 and obtained by the upper computer 8mjJ being a sensorAnd numbering to obtain the shock wave pressure test result of the explosive 9 to be tested.
And 7.3, processing the shooting result of the first high-speed camera 10 to obtain a shock wave track test result of the explosive 9 to be tested, namely obtaining the shock wave peak pressure P according to the shock wave peak pressure at the center r of the explosivemr。
After the shooting result of the first high-speed camera 10 is processed by the upper computer, the track of the distance x between the shock wave front and the explosive changing along with the time is obtained, and the x-t curve is subjected to nonlinear fitting by using the following formula:
wherein A isi、BiAre all fitting coefficients, AiReflecting the intensity of the shock wave, BiReflecting the attenuation time of the shock wave; c. C0Representing the sound velocity in water, 1.46 km/s; d is the detonation velocity of the explosive. Fitting to obtain formula coefficient Ai、BiThe obtained shock wave velocity is the normal velocity of the shock wave front, and the shock wave peak pressure P at the center r of the explosive is calculated according to the following formulamr：
Pmr＝ρ0usup
us＝1.483+25.306lg(1+up/5.19)
In the formula: rho0Is the density of water in g/cm3；usIs the shock wave velocity, and the unit is km/s; u. ofpThe velocity of the flow field particles after the shock wave is expressed in km/s. Therefore, the change curve of the explosion near-field shock wave pressure peak value along with the propagation distance can be obtained.
According to the experimental test results, the invention provides two methods for obtaining the time attenuation constant of the near-field shock wave:
according to the prior knowledge, the functional relation between the shock wave pressure P and the time t after the arrival of the shock wave is as follows:
P(t)＝Pm*e-t/θ
in the formula (I), the compound is shown in the specification,Pmis the peak value of the initial pressure of the shock wave in the water, and theta is the attenuation time constant of the shock wave.
The method comprises the following steps: optical pressure measurement combined method, when the radius R of the bubble reaches the jth sensor position, the time is t0In the above formula, P (t) is Pb，t＝t0，Pm＝PmjThen, the time constant of the jth sensor test point position can be obtained as θ:
the second method comprises the following steps: combined optometric measurement, with a bubble radius of R, for a time of t0Boundary pressure of air bubble is PbIn the variation curve of the near-field shock wave pressure peak value along with the propagation distance obtained by processing the shock wave track test result, when the explosive center distance R is equal to the bubble radius R, the shock wave peak value pressure is PmrThen P will beb、t0、PmrSubstituting the time constant into the formula according to the position r of the center of the explosive, wherein the time constant is theta:
in summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. Explosion near field shock wave time constant test system under water, its characterized in that includes: the device comprises a water tank (1), an assembling plate (2), a connecting plate (3), a supporting and positioning net rack (4), a PVDF sensor group (5), a signal conditioning instrument (6), a high-frequency data acquisition instrument (7), an upper computer (8), an explosive to be tested (9), a first high-speed camera (10), a second high-speed camera (11), a detonator (12) and a synchronous trigger device (13);
wherein, two transparent pressure-resistant observation windows are symmetrically arranged on the side wall of the water tank (1);
the supporting and positioning net rack (4) is used for limiting the initial position of the explosive to be tested (9) at the geometric center of the water tank (1), and the supporting and positioning net rack (4) is fixed at the middle position of the top opening of the water tank (1); the connecting plate (3) is limited by a groove arranged in the middle of the supporting and positioning net rack (4) and is fixedly connected with the supporting and positioning net rack (4);
the assembling plate (2) is used for fixing the explosive to be tested (9) and the PVDF sensor group (5), one end of the assembling plate (2) is fixedly connected with the connecting plate (3), and a through hole A is formed in the center of the other end of the assembling plate (2); the detonator assembling rod is of a hollow structure, one end of the detonator assembling rod is fixedly connected with the assembling plate (2) through a through hole, the center of the other end of the detonator assembling rod is provided with a groove, the detonator (12) is fixed in the groove of the detonator assembling rod, and a detonator wire of the detonator (12) penetrates through the detonator assembling rod and the through hole A and extends out of the water tank (1); the explosive (9) to be tested is fixed on the detonator (12); the detonator (12) is connected with the synchronous trigger device (13), and the synchronous trigger device (13) is connected with the upper computer (8);
a plurality of through square holes which are not in linear staggered arrangement are formed in the assembly plate (2) around the through hole A, and the first end of the sensor assembly plate is matched with the through square holes to fix the sensor assembly plate on the same side of the assembly plate (2); sensors in the PVDF sensor group (5) are respectively fixed on one side, facing the through hole A, of the second end of the sensor assembling plate; the PVDF sensor group (5) is sequentially connected with the signal conditioner (6), the high-frequency data acquisition instrument (7) and the upper computer (8);
the first high-speed camera (10) and the second high-speed camera (11) are both placed in front of the same observation window of the water tank (1), and the shooting center positions of the first high-speed camera (10) and the second high-speed camera (11) and the center of the explosive to be detected (9) are located on the same height horizontal plane; the second high-speed camera (11) is placed between the first high-speed camera (10) and the water tank (1); the first high-speed camera (10) and the second high-speed camera (11) are respectively connected with the synchronous trigger device (13) and the upper computer (8).
2. The underwater explosion near-field shock wave time constant testing system as claimed in claim 1, wherein the observation window is made of a transparent acrylic material plate, and the thickness of the observation window is set according to the explosion intensity of the explosive (9) to be tested.
3. The underwater explosion near-field shock wave time constant test system of claim 2, wherein the thickness of the observation window is 20mm to 30 mm.
4. The underwater explosion near-field shock wave time constant testing system of claim 1, wherein the observation window is made of multiple layers of explosion-proof glass.
5. The underwater explosion near field shock wave time constant testing system of claim 1, wherein a fixing plate is sleeved on the sensor assembling plate.
6. The method for testing the time constant of the underwater explosion near-field shock wave by using the system for testing the time constant of the underwater explosion near-field shock wave as claimed in any one of claims 1 to 5 is characterized by comprising the following steps of:
step 1, injecting water into the water tank (1) to a set position;
step 2, placing a scale at the geometric center of the water tank (1), and keeping the scale vertical to the cross section of the water tank (1); adjusting the positions and postures of the first high-speed camera (10) and the second high-speed camera (11), and focusing until the picture is clear;
step 3, adhering the PVDF sensor group (5) to the second end of the sensor assembling plate, inserting the sensor assembling plate into the through square hole on the assembling plate (2), enabling one side of a sensitive element to face the explosive to be tested (9), and performing waterproof treatment on a welding spot of the PVDF sensor group (5) connected with a cable; the PVDF sensor group (5), the signal conditioner (6), the high-frequency data acquisition instrument (7) and the upper computer (8) are connected in sequence;
step 4, fixedly connecting one end of the detonator assembling rod with the assembling plate (2), fixing the detonator (12) in a groove at the other end of the detonator assembling rod, and extending a detonator wire of the detonator (12) to the outside of the water tank (1) through the detonator assembling rod and the through hole A; installing the explosive (9) to be detected on the detonator (12), and performing waterproof treatment on the explosive (9) to be detected; the detonator (12) is connected with the synchronous trigger device (13), and the synchronous trigger device (13) is connected with the upper computer (8);
step 5, putting the connecting plate (3) and the assembling plate (2) into water, and assembling the connecting plate and the assembling plate at the central position of the supporting and positioning net rack (4);
step 6, confirming the state of the synchronous trigger device (13), and connecting a detonator line with a detonating cord;
step 7, evacuating personnel, synchronously triggering and detonating; the first high-speed camera (10) and the second high-speed camera (11) transmit the shooting results to the upper computer (8), and the upper computer (8) processes the shooting results to obtain the time constant of the near-field shock wave of the explosive to be detected (9).
7. The method for testing the time constant of the underwater explosion near-field shock wave according to claim 6, wherein in the step 7, the process that the upper computer (8) processes the shooting result to obtain the time constant of the near-field shock wave of the explosive (9) to be tested comprises the following steps:
and 7.1, recording the time from the initiation to the bubble radius R as t according to the bubble form shot by the second high-speed camera (11)0The boundary pressure P of the bubble at this time is calculated by the following formulab：
Wherein Q isvThe unit of the explosion heat of the explosive (9) to be detected is J/g; w is the explosive loading quantity of the explosive (9) to be detected, and the unit is g; r is the bubble radius, and the unit is m;
7.2, obtaining the shock wave peak pressure P of the position of each sensor according to the PVDF sensor group (5)mjJ is the serial number of the sensor, and the shock wave pressure test result of the explosive (9) to be tested is obtained;
and 7.3, obtaining a track of the distance x between the shock wave front and the explosive along with the change of time according to the shooting result of the first high-speed camera (10), and carrying out nonlinear fitting on an x-t curve by using the following formula:
wherein A isi、BiAre all fitting coefficients, AiReflecting the intensity of the shock wave, BiReflecting the length of the decay time of the shock wave, c0Representing the sound velocity in water, and D is the detonation velocity of the explosive (9) to be detected;
fitting to obtain coefficient Ai、BiAnd differentiating to obtain the shock wave velocity, and calculating by adopting the following formula to obtain the shock wave peak pressure P at the center r of the explosive (9) to be testedmr：
Pmr＝ρ0usup
Where ρ is0Density of water in g/cm 3; u. ofsIs the shock wave velocity, and the unit is km/s; u. ofpThe unit is km/s of the velocity of flow field particles after the shock wave, so that a change curve of the pressure peak value of the shock wave of the explosion near field along with the propagation distance is obtained;
step 7.4, setting the time t when the radius R of the bubble reaches the position of the jth sensoroLet P (t) be Pb，t＝t0，Pm＝PmjThen, the time constant of the jth sensor test point position is obtained as θ:
8. the underwater explosion near field shock wave time constant test method according to claim 7, wherein the time constant in the step 7.4 is calculated by adopting the following method:
let the time taken be t when the radius of the bubble is RoBoundary pressure of air bubble is PbIn the variation curve of the near-field shock wave pressure peak value along with the propagation distance obtained by processing the shock wave track test result, when the explosive center distance R is equal to the bubble radius R, the shock wave peak value pressure is PmrAnd obtaining the time constant theta according to the r position of the explosive center:
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