A prediction method for deep-sea plume heat source flux and source buoyancy flux and its application

Abstract

The present invention relates to the field of prediction methods for heat source flux and source buoyancy flux of plumes, and specifically to a prediction method for heat source flux and source buoyancy flux of deep-sea plumes, including: S1, obtaining a semi-empirical formula for the maximum rising height and neutral buoyancy layer height of a single-vent hydrothermal plume; S2, constructing an amplification factor model for double-vent submarine hydrothermal plumes with different intensities; S3, calculating the amplification coefficient of the neutral buoyancy layer height; S4 prediction of source buoyancy flux and heat source flux. The present invention overcomes the blank in the field of prediction methods for heat source flux and source buoyancy flux in the case of mixing of two submarine hydrothermal plumes with different source intensities, and is helpful to further study submarine energy cycle and material cycle.

Description

Technical Field

[0001] The invention relates to the field of prediction methods for heat source flux and source buoyancy flux of plumes, and in particular to a prediction method and application of heat source flux and source buoyancy flux of deep-sea plumes. Background Art

[0002] Seafloor hydrothermal plumes are an important part of the material and energy cycle of the ocean and lithosphere. Unique biological communities are also formed around hydrothermal plumes, and some unique species are completely dependent on the heat and chemicals transferred by hydrothermal fluids.

[0003] At present, there are two methods to measure plume dynamics. One is based on experimental or measured images combined with particle image velocimetry (PIV) to obtain plume dynamics; the other is to obtain plume dynamics through numerical simulation. Among them, numerical simulation can study the rise and development process of plumes more conveniently and accurately, and is an important means to study the material and energy exchange process between plumes and surrounding seawater on a larger space and longer time scale.

[0004] Through numerical simulation methods, the flow field structure and dynamic characteristics of a single hydrothermal plume have been studied in depth. However, in actual hydrothermal areas, the distribution of hydrothermal vents is often dense. When two hydrothermal vents are close enough, the mutual mixing of hydrothermal plumes will cause changes in their flow field structure and dynamic characteristics. Therefore, the numerical simulation results of a single-vent hydrothermal plume are not applicable to a hydrothermal environment with multiple vents.

[0005] At present, there is no precedent for the study of heat source flux and source buoyancy flux of two submarine hydrothermal plumes with different source strengths; and different hydrothermal vents in the same hydrothermal area often have different source strengths. Heat source flux and source buoyancy flux reflect the energy and material exchange between the ocean and the lithosphere of submarine hydrothermal plumes. Studying the heat source flux and source buoyancy flux in the case of mixing of two submarine hydrothermal plumes with different source strengths is of great significance to the development and utilization of marine resources. Summary of the invention

[0006] The purpose of the present invention is to solve the problem of large errors in the estimation methods of hydrothermal plume source buoyancy flux and heat source flux, and to provide a prediction method for calculating the heat source flux and source buoyancy flux of dual-vent hydrothermal plumes using a plume neutral buoyancy layer height model when two seabed hydrothermal plumes with different source intensities are mixed.

[0007] A method for predicting heat source flux and source buoyancy flux of a deep-sea plume, wherein the deep-sea plume is a double-vent hydrothermal plume, comprising the following steps:

[0008] S1. Semi-empirical formula Z for obtaining the neutral buoyancy layer height of a single vent hydrothermal plume neutral =Cneutral (B exit N -3 ) 1 / 4 ,

[0009] Among them, C neutral is the empirical coefficient in the semi-empirical calculation formula of the neutral buoyancy layer height of a single vent hydrothermal plume; N is the background buoyancy frequency, and the calculation formula is as follows:

[0010] in B is the rate of change of seawater density relative to seawater depth in the depth density function of the current sea area; exit is the source buoyancy flux, and is affected by the nozzle mass flow rate Q exit Impact. exit and Q exit The calculation formula is as follows:

[0011]

[0012] Among them, ρ exit is the density of the hydrothermal fluid within the hydrothermal eruption height range, ρ bottom is the density of the bottom of the seawater, g is the acceleration due to gravity, which is 9.81 m / s 2 ;

[0013] Q exit =πr 2 V exit

[0014] V exit is the eruption velocity of the hydrothermal plume; r is the radius of the vent

[0015] Using Ansys fluent software, adopting the realizable k-ε model, setting several groups of working conditions, and performing numerical simulation, C is obtained through data fitting. neutral The value of

[0016] S2. Based on the semi-empirical formula, a model of amplification factors of double-vent submarine hydrothermal plumes with different intensities is constructed:

[0017] Assume that the severity of the external influence on the hydrothermal plume is related to the intensity of the two eruptions. When two submarine hydrothermal plumes with different source intensities merge, the rise height of a single plume is affected by the source buoyancy flux ratio of the two plumes, F. * The influence of; the amplification factor model of the double-vent submarine hydrothermal plumes with different intensities is obtained as follows;

[0018]

[0019] Among them, C0 to C4 are undetermined coefficients that need to be determined by nonlinear fitting;

[0020] The physical quantity represented by Ri is the ratio of buoyancy to momentum, and the calculation formula is as follows:

[0021]

[0022] In a dual-vent hydrothermal system, the source buoyancy flux ratio F of the two vents is obtained by the following formula: * and source separation degree L *

[0023]

[0024] Among them, B 1ex , B 2exi represent the source buoyancy flux of the hydrothermal vent in the dual-vent system; the subscripts 1 and 2 represent the source buoyancy flux of the hydrothermal vent in the dual-vent system

[0025] Parameters of the first and second nozzles

[0026] In a dual-vent hydrothermal system, the source separation degree L of the two vents is obtained by the following formula: *

[0027] L * =L / (B exit N -3 ) 1 / 4

[0028] L represents the distance between the two nozzles;

[0029] S3. Calculating the amplification factor of the neutral buoyancy layer height based on the amplification factor model;

[0030] S4. Based on the amplification factor, predict the source buoyancy flux and the heat source flux.

[0031] Preferably, the S3 specifically comprises the following steps:

[0032] Using Ansys fluent software, the realizable k-ε model was used to set several groups of working conditions for numerical simulation to extract the neutral buoyancy layer height Z of the double-nozzle hydrothermal plume. 2,neutral The data, through ξ neutral =Z 2,neutral / Z neutral , and the magnification factor ξ of the neutral buoyancy layer height is obtained neutral Data of the neutral buoyancy layer height Z of the hydrothermal plume through the double vents 2,neutral The data and the magnification factor ξ of the neutral buoyancy layer height neutral Data pair Fitting is performed to obtain the magnification factor ξ of the neutral buoyancy layer height neutral The calculation formula is as follows:

[0033]

[0034] Preferably, the S4 specifically comprises the following steps:

[0035] Get the depth density function of the current sea area;

[0036] Obtain the neutral buoyancy layer heights of the first and second nozzles in the double-nozzle hydrothermal system to be tested, which are recorded as h1 and h2 respectively;

[0037] The nozzle temperatures T1 and T2 of the first nozzle and the second nozzle and the seawater bottom temperature Tb;

[0038] The distance L between the first nozzle and the second nozzle

[0039] Obtain the temperature density function within the hydrothermal eruption height range, and obtain the hydrothermal density ρ within the hydrothermal eruption height range based on the nozzle temperatures T1 and T2 of the first nozzle and the second nozzle 1exit , 2exit , based on the seawater bottom temperature Tb, the seawater bottom density ρ is obtained bottom

[0040] ρ bottom , h1 and h2, L, ρ 1exit , 2exit , substitute into the following formula, where the subscripts 1 and 2 represent the corresponding parameters of the first and second nozzles in the dual nozzle system, respectively, to obtain a two-variable equation system;

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048] By solving the two-dimensional equation system, we can obtain the source buoyancy flux B of the two nozzles: 1exit , B 2exit

[0049] Obtain the temperature specific heat capacity function within the hydrothermal eruption height range, and obtain the specific heat capacity C of the hydrothermal fluids at the first and second vents based on the vent temperatures T1 and T2 of the first and second vents. 1p, C 2p , the heat source flux H1 of the first nozzle is obtained as shown in the following formula:

[0050] H1=ρ 1exit C 1p (T1-Tb)Q 1exit

[0051] The heat source flux H2 of the second nozzle is obtained as shown in the following formula:

[0052] H2=ρ 2exit C 2p (T2-Tb)Q 2exit

[0053] Preferably, in step 4, the C neutral The value of is 1.85.

[0054] The present invention also provides a method for predicting heat source flux and source buoyancy flux of a double-vent hydrothermal plume, and its application in the Longqi hydrothermal area in the southwest Indian Ocean, comprising the following steps:

[0055] Simplify the Long Hydrothermal Area environment;

[0056] Simplify the seawater temperature gradient δT(Z) / Z in the Longqi hydrothermal area and calculate the seafloor temperature Tb;

[0057] Where T(Z) is the vertical temperature distribution of the Longqi hydrothermal area, and Z is the seawater depth;

[0058] Calculate the nozzle spacing L;

[0059] Determine the height of the neutral buoyancy layer at the nozzle;

[0060] Obtain the temperature-density function and temperature-specific heat capacity function of seawater under high temperature and high pressure environment;

[0061] Piecewise linear simplification of seawater temperature-density function under high temperature and high pressure environment, simplification of seawater temperature-specific heat capacity function under high temperature and high pressure environment;

[0062] Prediction of source buoyancy flux and heat source flux in Longqi hydrothermal area;

[0063] Based on the nozzle temperatures T1 and T2 of the first and second nozzles, the density of the hydrothermal fluid during the hydrothermal eruption is obtained by combining the physical property function of seawater. 1exit , 2exit , based on the seawater bottom temperature Tb, the seawater bottom density ρ is obtained bottom ;

[0064] ρ bottom , h1 and h2, L, ρ 1exit , 2exit, substitute into the following formula, where the subscripts 1 and 2 represent the corresponding parameters of the first and second nozzles in the dual nozzle system, respectively, to obtain a two-variable equation system;

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072] By solving the two-dimensional equation system, we can obtain the source buoyancy flux B of the two nozzles: 1exit , B 2exit

[0073] Obtain the temperature specific heat capacity function within the hydrothermal eruption height range, and obtain the specific heat capacity C of the hydrothermal fluids at the first and second vents based on the vent temperatures T1 and T2 of the first and second vents. 1p , C 2p , the heat source flux H1 of the first nozzle is obtained as shown in the following formula:

[0074] H1=ρ 1exit C 1p (T1-Tb)Q 1exi

[0075] The heat source flux H2 of the second nozzle is obtained as shown in the following formula:

[0076] H2=ρ 2exit C 2p (T2-Tb)Q 2exit .

[0077] Preferably, the seawater temperature gradient of the Longqi hydrothermal area is δT(Z) / Z=0.001°C / m, and the seafloor temperature Tb is 1.89°C;

[0078] The nozzle spacing L is 35m;

[0079] The neutral buoyancy layer height of the nozzle is in the range of 200m-250m;

[0080] Based on the seawater depth of 27MPa and salinity of 34.98PSU in the Longqi hydrothermal area, the seawater temperature-density function under the simplified high temperature and high pressure environment is:

[0081]

[0082] The simplified seawater temperature-specific heat capacity function under high temperature and high pressure environment is:

[0083] f2(T)=4967-5.74468T+0.00833907*T 2

[0084] Where T is the seawater temperature, f1(T) is the density, and f2(T) is the specific heat capacity;

[0085] The nozzle temperatures T1 and T2 of the first nozzle and the second nozzle are set to 370°C, then the density ρ 1exit , 2exit Both 750Kg / m 3 , the seawater bottom density ρ bottom 1039Kg / m 3

[0086] By solving the two-dimensional equation group, the source buoyancy flux B of the first nozzle and the second nozzle is obtained: 1exit , B 2exit 0.1648m respectively 4 / s 3 and 0.1176m 4 / s 3 ;

[0087] The specific heat capacity C of the hot liquid in the first nozzle and the second nozzle 1p , C 2p Both are 4721 J / Kg*K, and the heat source fluxes H1 and H2 of the first nozzle and the second nozzle are 80 MW and 57 MW respectively.

[0088] Compared with the prior art, the present invention has the following beneficial effects:

[0089] 1. The data of the constructed double-vent hydrothermal plume neutral buoyancy layer height amplification factor model comes from the numerical simulation of double-vent hydrothermal plumes, and the amplification factor model is derived based on the double-vent plume jet phenomenon. In actual hydrothermal areas, the distribution of hydrothermal vents is often dense. When the distance between two hydrothermal vents is close enough, the mutual mixing between the hydrothermal plumes will cause changes in their flow field structure and dynamic characteristics. Therefore, the neutral buoyancy layer height model of single-vent and double-vent hydrothermal plumes of equal intensity is not suitable for complex multi-vent hydrothermal environments. Therefore, the constructed double-vent hydrothermal plume neutral buoyancy layer height amplification factor model has a wider range of applicability than the single-vent and double-vent hydrothermal plume neutral buoyancy layer height model. Therefore, the hydrothermal plume source buoyancy flux and heat source flux estimation method based on this amplification factor model has a wider range of applicability and higher estimation accuracy.

[0090] 2. The prediction method of heat source flux and source buoyancy flux of dual-vent hydrothermal plumes based on the height amplification factor model of the neutral buoyancy layer of dual-vent hydrothermal plumes and the height of the neutral buoyancy layer of the plumes (required parameters: neutral buoyancy layer height and vent spacing) requires less detection data than the traditional method of estimating the heat source flux and source buoyancy flux of seafloor hydrothermal plumes through the neutral buoyancy layer (required parameters: potential temperature difference between the neutral buoyancy layer and the seawater background, the diameter of the neutral buoyancy layer, the thickness of the neutral buoyancy layer and the average flow velocity of seawater). It is more convenient when studying the energy cycle and material cycle of the seafloor. BRIEF DESCRIPTION OF THE DRAWINGS

[0091] In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the specific implementation or the prior art description. Some specific embodiments of the present invention will be described in detail in an exemplary but not restrictive manner with reference to the drawings. The same reference numerals in the drawings indicate the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0092] Figure 1 Simulation results of single-nozzle hydrothermal plume: Z max and Z neutral

[0093] Figure 2 The calculation domain and grid division diagram of the hydrothermal plume, where: (a) is the schematic diagram of the model calculation domain, (b) is the grid division of the entire calculation domain, and (c) is the grid division of the near-vent area.

[0094] Figure 3 This is a comparison chart of the amplification factor results of the semi-empirical formula for maximum rising height.

[0095] Figure 4 This is a comparison chart of the amplification factor results of the semi-empirical formula for the neutral buoyancy layer height.

[0096] Figure 5 Distribution map of vents and CTD stations in Longqi hydrothermal area

[0097] Figure 6 Turbidity changes at CTD stations in Longqi hydrothermal area

[0098] Figure 7 Potential temperature changes at the CTD station in the Longqi hydrothermal area

[0099] Figure 8 Seawater physical property functions in the Longqi hydrothermal area DETAILED DESCRIPTION

[0100] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0101] Example 1

[0102] Step 1: Obtain the semi-empirical formula for the maximum rise height and neutral buoyancy layer height of a single-vent hydrothermal plume

[0103] The simulation of the double-vent submarine hydrothermal plume is based on the simulation of the single-vent plume. Therefore, in order to calculate the rise height of the double-vent submarine hydrothermal plume, it is necessary to first determine the semi-empirical formula for the characteristic height of the single-vent hydrothermal plume. According to the inference of the MTT model, it can be known that the semi-empirical formulas for the maximum rise height and the neutral buoyancy layer height of the single-vent hydrothermal plume are Z max =C ma (B exit N -3 ) 1 / 4 and Z neutral =C neutral (B exit N -3 ) 1 / 4 .

[0104] Among them, C neutral and C max is the empirical coefficient in the semi-empirical calculation formula of the neutral buoyancy layer height of a single vent hydrothermal plume; N is the background buoyancy frequency, and the calculation formula is as follows:

[0105] in It is the changing rate of seawater density relative to seawater depth in the depth density function of the current sea area;

[0106] B exit is the source buoyancy flux, and is affected by the nozzle mass flow rate Q exit Impact. exit and Q exit The calculation formula is as follows:

[0107] Among them, ρ exit is the density of the hydrothermal fluid within the hydrothermal eruption height range, ρ bottom is the density of the bottom of the seawater, g is the acceleration due to gravity, which is 9.81 m / s 2 ;

[0108] Q exit =πr 2 V exit

[0109] V exitis the eruption velocity of the hydrothermal plume; r is the radius of the vent

[0110] Using Ansys fluent software, based on the fact that the hydrothermal plume vent can be equivalent to a circle and there is an initial momentum during the eruption, a realizable k-ε model that can better simulate cylindrical jets is used. By modifying the vent parameter settings (vent velocity, vent temperature, etc.) and the background environment settings (background temperature gradient) to set up a comparison group, the development process of deep-sea hydrothermal plumes in a stratified environment is simulated and parameter sensitivity analysis is performed. The working condition settings and simulation results of each group are shown in Table 1.

[0111] Table 1 Single nozzle plume simulation condition settings and results

[0112]

[0113] The characteristic height of the plume (Z neutral , C max ) value. neutral , C max ), source buoyancy flux B exit By fitting the data with the background buoyancy frequency N, the semi-empirical formulas for the maximum rise height of the plume and the height of the neutral buoyancy layer are obtained: Z max =2.51(B exit N -3 ) 1 / 4 , Z neutral =1.85(B exit N -3 ) 1 / 4 The fitting results and the correlation index R 2 like Figure 1 shown.

[0114] Step 2: Construct a model of the amplification factor of dual-vent submarine hydrothermal plumes with different intensities

[0115] Some scholars have conducted research on the characteristic height of hydrothermal plumes from dual vents of equal intensity. The results are as follows:

[0116]

[0117] Among them, C1 to C4 are undetermined coefficients that need to be determined by nonlinear fitting;

[0118] The physical quantity represented by Ri is the ratio of buoyancy to momentum, and the calculation formula is as follows:

[0119]

[0120] L * =L / (B exit N-3 ) 1 / 4

[0121] L represents the distance between the two nozzles.

[0122] Assume that the severity of the external influence on the hydrothermal plume is related to the intensity of the two eruptions. When two submarine hydrothermal plumes with different source intensities merge, the rise height of a single plume is affected by the source buoyancy flux ratio of the two plumes, F. * When the source separation degree L * When the two nozzles are mixed into a source buoyancy flux enhancement (F * +1) times the single vent hydrothermal plume, so without considering the influence of other factors, The physical quantity represented by the Richardson number Ri is the ratio of buoyancy to momentum. When two plumes mix, the buoyancy flux and mass flux of the hydrothermal plume will change. Therefore, a coefficient that can reflect the severity of its impact is added on the basis of maintaining the original formula. Finally, the formula for the amplification factor of the double-vent submarine hydrothermal plumes with different intensities is obtained as follows:

[0123]

[0124] Among them, C0 to C4 are undetermined coefficients that need to be determined by nonlinear fitting;

[0125] In a dual-vent hydrothermal system, the source buoyancy flux ratio F of the two vents is obtained by the following formula: *

[0126]

[0127] Among them, B 1exit , B 2exit They represent the source buoyancy flux of one nozzle in a dual nozzle system; the subscripts 1 and 2 represent the parameters of the first and second nozzles in the dual nozzle system respectively.

[0128] In order to determine the numerical values ​​of C0 to C4, a comparison group was set by modifying the nozzle parameter settings (nozzle velocity, source buoyancy flux ratio) and background environment settings (source separation degree). The development process of deep-sea hydrothermal plumes in a stratified environment was simulated and parameter sensitivity analysis was performed. The working condition settings and simulation results of each group are shown in Table 2.

[0129] Table 2 Simulation environment and result summary of double-nozzle hydrothermal plume conditions with different intensities

[0130]

[0131] The dynamic characteristics of hydrothermal plumes are mainly controlled by buoyancy and momentum. The process of plume rise and horizontal diffusion is in a turbulent state, so the controlling equations are the density-weighted unsteady Reynolds average mass equation, momentum equation and energy equation.

[0132] In terms of calculation domain setting, the hydrothermal vent is equivalent to a circular vent with a height from the bottom h0 = 2m and a vent radius r = 0.1m. In addition, the calculation domain of the numerical simulation is approximately a rectangle, as shown in the schematic diagram Figure 2 a. There is a symmetry plane in the entire computational domain. The nozzle is the velocity inlet. The top and bottom of the computational domain are the pressure outlet and the no-slip wall, respectively. For the grid drawing, the numerical simulation uses the Triangles method. Based on the research of Suzuki et al., 1 / 10 of the nozzle radius is selected as the minimum grid size, and the grid expansion rate is set to 1.03. Finally, the fluid computational domain is divided into about 9 million units, such as Figure 2 b and Figure 2 As shown in c.

[0133] In order to achieve convergence in the simulation, the momentum, turbulent kinetic energy, turbulent dissipation rate, and energy equations are all discretized using the Third-Order MUSCL (third-order monotone upstream-centered schemes for conservation laws,) format. The pressure equation is discretized using the PRESTO! (Pressure Staggering Option) method, the gradient algorithm uses the node-based Green-Gauss method (Green-Gauss node based), the pressure-velocity coupling scheme uses the PISO (pressure-implicit with splitting of operators) scheme, and the time discretization uses the second-order implicit format.

[0134] Based on the research results of Andrew et al., the rise time t of the hydrothermal plume is of the same order of magnitude as the inverse of the background buoyancy frequency 1 / N. In order to investigate the various processes of the hydrothermal plume developing to a quasi-steady state, the simulation time of each condition is taken as 3t. * , where t * =2π / N is the buoyancy period. At the same time, a time step of 0.5 s is selected so that the calculation in a single time step can reach convergence within 30 iterations (the total residuals of each physical quantity in two consecutive iterations are less than 10e-3, and the total residual of energy is less than 10e-6).

[0135] Step 3: Calculate the amplification factor of the neutral buoyancy layer height

[0136] Using CFD-post post-processing software to extract the neutral buoyancy layer height Z of the double-vent hydrothermal plume 2,max The data of Z 2,max The data are consistent with the F in Table 2 * , L * , Ri are fitted nonlinearly to obtain the maximum rise height amplification factor ξ max The formula has a stability of 0.898. Figure 3 is the maximum rise height magnification factor ξ max The simulation results and calculation results of the formula are fitted to obtain the semi-empirical formula for the maximum rise height of double-nozzle plumes with different intensities, which has a high correlation coefficient (0.898), as shown below.

[0137]

[0138] It can be seen from Table 2 that the neutral buoyancy layer height Z of the double nozzle plume is 2,neutral With maximum rise height Z 2,max The ratio of Z is still consistent with the results of a single nozzle (stable at around 0.7 in Table 3). 2,max The data are consistent with the F in Table 2 * , L * , Ri are fitted nonlinearly, the structure of the semi-empirical formula of the neutral buoyancy layer still conforms to the scaling formula of the maximum rise height, and only the coefficients are modified. After calculation, the amplification coefficient ξ of the neutral buoyancy layer height is obtained neutral The calculation formula of Figure 4 It is a comparison between the amplification factor obtained by simulation and the amplification factor calculated by formula. The results show that the two have a high correlation.

[0139]

[0140] Step 4: Prediction of source buoyancy flux and heat source flux

[0141] The background buoyancy frequency N of seawater is determined based on the data of vertical density changes of actual sea conditions. Based on the detection of the turbidity sensor, the height of the neutral buoyancy layer of the first and second vents is determined, recorded as h1 and h2 respectively. The seawater temperature-density function under fixed pressure and salinity is determined based on the seawater depth and salinity information, and the density ρ of the hydrothermal fluid within the hydrothermal eruption height range is obtained based on the vent temperatures T1, T2, and Tb of the first and second vents. 1exit , 2exit and the seawater bottom density ρ bottom Finally, the distance L between the first nozzle and the second nozzle in the double-nozzle hydrothermal system to be tested is obtained. bottom, h1 and h2, L, ρ 1exit , 2exit , substitute into the following formula, where the subscripts 1 and 2 represent the corresponding parameters of the first and second nozzles in the dual nozzle system, respectively, to obtain a set of two-variable equations.

[0142]

[0143]

[0144]

[0145]

[0146]

[0147]

[0148]

[0149] By solving the two-dimensional equation system, we can obtain the source buoyancy flux B of the two nozzles: 1exit , B 2exit

[0150] The seawater temperature-specific heat capacity function at a fixed pressure and salinity is determined according to the seawater depth and salinity information. Based on the nozzle temperatures T1 and T2 of the first nozzle and the second nozzle, the specific heat capacity C of the hot liquid at the first nozzle and the second nozzle is obtained. 1p , C 2p , the heat source fluxes H1 and H2 of the first nozzle and the second nozzle are obtained as shown in the following formula:

[0151] H1=ρ 1exit C 1p (T1-Tb)Q 1exit

[0152] H2=ρ 2exit C 2p (T2-Tb)Q 2exit

[0153] Example 2

[0154] A prediction method for heat source flux and source buoyancy flux of double-vent hydrothermal plumes with application in Longqi hydrothermal area

[0155] Figure 5-7 The environment of the Longqi hydrothermal area is shown. Figure 5 The CTD station and vent station locations in the Longqi hydrothermal area are shown. Based on the longitude and latitude of the active vents DFF3 and DFF6, the vent spacing L is calculated to be 35m. Figure 6The turbidity changes at each station are shown. Based on the two turbidity anomalies at CTD03-3, it can be seen that the neutral buoyancy layer height range of the active vents DFF3 and DFF6 is 200m-250m. Figure 7 The potential temperature changes at each station are displayed, and the vertical seawater potential temperature in the water depth range of 2000m-2400m is simplified to a linear change. Through multiple fittings, the temperature gradient of the Longqi environment is judged to be 0.001℃ / m, and the seabed temperature Tb is calculated to be 1.89℃.

[0156] Based on the seawater depth (27MPa) and salinity (34.98PSU) of the Longqi hydrothermal area, according to the research of some scholars, the physical property function of seawater in the Longqi hydrothermal area can be obtained. The results are as follows: Figure 8 As shown. The piecewise linear simplification of the seawater temperature-density function under high temperature and high pressure environment, the result is as follows:

[0157]

[0158] Simplifying the seawater temperature-specific heat capacity function under high temperature and high pressure environment, the results are as follows:

[0159] f2(T)=4967-5.74468T+0.00833907*T 2

[0160] The temperature of the active hydrothermal vents in the Longqi hydrothermal area is generally higher than 350°C. For the convenience of calculation, the vent temperatures T1 and T2 of the active vents DFF3 and DFF6 are set to 370°C. Based on the seawater temperature-density function, it can be known that the density of the hydrothermal fluid during the eruption of the two active vents is 1exit , 2exit 750Kg / m 3 The seawater bottom density ρ is obtained based on the seawater bottom temperature Tb bottom 1039Kg / m 3 .

[0161] N、ρ bottom , h1 and h2, L, ρ 1exit , 2exit , substitute into the following formula, where the subscripts 1 and 2 represent the corresponding parameters of the first and second nozzles in the dual nozzle system, respectively, to obtain a set of two-variable equations.

[0162]

[0163]

[0164]

[0165]

[0166]

[0167]

[0168]

[0169] By solving the two-dimensional equation system, we can obtain the source buoyancy flux B of the two nozzles: 1exit , B 2exit 0.1648m respectively 4 / s 3 and 0.1176m 4 / s 3

[0170] The seawater temperature-specific heat capacity function at a fixed pressure and salinity is determined according to the seawater depth and salinity information. Based on the nozzle temperatures T1 and T2 of the first nozzle and the second nozzle, the specific heat capacity C of the hot liquid at the first nozzle and the second nozzle is obtained. 1p , C 2p The heat source fluxes H1 and H2 of the first and second nozzles are 80MW and 57MW respectively according to the following formula:

[0171] H1=ρ 1exit C 1p (T1-Tb)Q 1exit

[0172] H2=ρ 2exit C 2p (T2-Tb)Q 2exit

[0173] The above descriptions are only some specific implementation methods of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person familiar with the art within the technical scope disclosed in the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for predicting heat source flux and source buoyancy flux of a deep-sea plume, wherein the deep-sea plume is a double-vent hydrothermal plume, characterized in that: The following steps are involved: S1. Semi-empirical formula Z for obtaining the neutral buoyancy layer height of a single vent hydrothermal plume neutral =C neutral (B exit N -3 ) 1 / 4 , Among them, C neutral is the empirical coefficient in the semi-empirical calculation formula of the neutral buoyancy layer height of a single vent hydrothermal plume; N is the background buoyancy frequency, and the calculation formula is as follows: in It is the changing rate of seawater density relative to seawater depth in the depth density function of the current sea area; B exit is the source buoyancy flux, and is affected by the nozzle mass flow rate Q exit Impact; B exit and Q exit The calculation formula is as follows: Among them, ρ exit is the density of the hydrothermal fluid within the hydrothermal eruption height range, ρ bottom is the density of the bottom of the seawater, g is the acceleration due to gravity, which is 9.81 m / s 2 ; Q exit =πr 2 V exit V exit is the eruption velocity of the hydrothermal plume; r is the radius of the vent Using Ansys fluent software, adopting the realizable k-ε model, by modifying the nozzle parameter settings and background environment settings, setting several groups of working conditions, and performing numerical simulation, C neutral The value of S2. Based on the semi-empirical formula, a model of amplification factors of double-vent submarine hydrothermal plumes with different intensities is constructed: Assume that the severity of the external influence on the hydrothermal plume is related to the intensity of the two eruptions. When two submarine hydrothermal plumes with different source intensities merge, the rise height of a single plume is affected by the source buoyancy flux ratio of the two plumes, F. * The influence of; the amplification factor model of the double-vent submarine hydrothermal plumes with different intensities is obtained as follows; Among them, C0 to C4 are undetermined coefficients that need to be determined by nonlinear fitting; The physical quantity represented by Ri is the ratio of buoyancy to momentum, and the calculation formula is as follows: In a dual-vent hydrothermal system, the source buoyancy flux ratio F of the two vents is obtained by the following formula: * and source separation degree L * Among them, B 1exit , B 2exit represent the source buoyancy flux of the hydrothermal vent in the dual-vent system; the subscripts 1 and 2 represent the parameters of the first and second vents in the dual-vent system, respectively. In a dual-vent hydrothermal system, the source separation degree L of the two vents is obtained by the following formula: * L * =L / (B exit N -3 ) 1 / 4 L represents the distance between the two nozzles; S3. Calculating the amplification factor of the neutral buoyancy layer height based on the amplification factor model; S4. Based on the amplification factor, predict the source buoyancy flux and the heat source flux.

2. The method for predicting deep-sea plume heat source flux and source buoyancy flux according to claim 1, characterized in that: The S3 specifically includes the following steps: Using Ansys fluent software, the realizable k-ε model was used to set up several groups of working conditions for numerical simulation to extract the neutral buoyancy layer height Z of the double-vent hydrothermal plume. 2,neutral The data, through ξ neutral =Z 2,neutral / Z neutral , and the magnification factor ξ of the neutral buoyancy layer height is obtained neutral Data of the neutral buoyancy layer height Z of the hydrothermal plume through the double vents 2,neutral The data and the magnification factor ξ of the neutral buoyancy layer height neutral Data pair Fitting is performed to obtain the magnification factor ξ of the neutral buoyancy layer height neutral The calculation formula is as follows:

3. The method for predicting deep sea plume heat source flux and source buoyancy flux according to claim 2, characterized in that: The S4 specifically comprises the following steps: Get the depth density function of the current sea area; Obtain the neutral buoyancy layer heights of the first and second nozzles in the double-nozzle hydrothermal system to be tested, which are recorded as h1 and h2 respectively; The nozzle temperatures T1 and T2 of the first nozzle and the second nozzle and the seawater bottom temperature Tb; The distance L between the first nozzle and the second nozzle Obtain the temperature density function within the hydrothermal eruption height range, and based on the nozzle temperatures T1 and T2 of the first nozzle and the second nozzle, obtain the density ρ of the hydrothermal fluid within the hydrothermal eruption height range 1exit , 2exit , based on the seawater bottom temperature Tb, the seawater bottom density ρ is obtained bottom ; ρ bottom , h1 and h2, L, ρ 1exit , 2exit , substitute into the following formula, where the subscripts 1 and 2 represent the corresponding parameters of the first and second nozzles in the dual nozzle system, respectively, to obtain a two-variable equation system; By solving the two-dimensional equation system, we can obtain the source buoyancy flux B of the two nozzles: 1exit , B 2exit Obtain the temperature specific heat capacity function within the hydrothermal eruption height range, and obtain the specific heat capacity C of the hydrothermal fluids at the first and second vents based on the vent temperatures T1 and T2 of the first and second vents. 1p , C 2p , the heat source flux H1 of the first nozzle is obtained as shown in the following formula: H1=ρ 1exit C 1p (T1-Tb)Q 1exit The heat source flux H2 of the second nozzle is obtained as shown in the following formula: H2=ρ 2exit C 2p (T2-Tb)Q 2exit 。 4. The method for predicting deep sea plume heat source flux and source buoyancy flux according to claim 3, characterized in that: In step 4, the C neutral The value of is 1.

85.

5. The application of the method for predicting deep-sea plume heat source flux and source buoyancy flux as claimed in claim 4 in hydrothermal areas, characterized in that: The following steps are involved: Simplify the hydrothermal area environment; Simplify the seawater temperature gradient δT(Z) / Z in the hydrothermal area and calculate the seafloor temperature Tb; Where T(Z) is the vertical temperature distribution of the hydrothermal area, and Z is the seawater depth; Calculate the nozzle spacing L; Determine the height of the neutral buoyancy layer at the nozzle; Obtain the temperature-density function and temperature-specific heat capacity function of seawater under high temperature and high pressure environment; Piecewise linear simplification of seawater temperature-density function under high temperature and high pressure environment, simplification of seawater temperature-specific heat capacity function under high temperature and high pressure environment; Prediction of source buoyancy flux and heat source flux in hydrothermal areas; Based on the nozzle temperatures T1 and T2 of the first and second nozzles, the density of the hydrothermal fluid during the hydrothermal eruption is obtained by combining the physical property function of seawater. 1exit , 2exit The seawater bottom density ρ is obtained based on the seawater bottom temperature Tb bottom ; ρ bottom , h1 and h2, L, ρ 1exit , 2exit , substitute into the following formula, where the subscripts 1 and 2 represent the corresponding parameters of the first and second nozzles in the dual nozzle system, respectively, to obtain a two-variable equation system; By solving the two-dimensional equation system, we can obtain the source buoyancy flux B of the two nozzles: 1exit , B 2exit ; Obtain the temperature specific heat capacity function within the hydrothermal eruption height range, and obtain the specific heat capacity C of the hydrothermal fluids at the first and second vents based on the vent temperatures T1 and T2 of the first and second vents. 1p , C 2p , the heat source flux H1 of the first nozzle is obtained as shown in the following formula: H1=ρ 1exit C 1p (T1-Tb)Q 1exit The heat source flux H2 of the second nozzle is obtained as shown in the following formula: H2=ρ 2exit C 2p (T2-Tb)Q 2exit 。 6. The use according to claim 5, characterized in that The seawater temperature gradient in the hydrothermal area is 0.001°C / m, and the seafloor temperature Tb is 1.89°C; The nozzle spacing L is 35m; The neutral buoyancy layer height of the nozzle is in the range of 200m-250m; Based on the seawater depth of 27 MPa and salinity of 34.98 PSU in the hydrothermal area, the seawater temperature-density function under the simplified high temperature and high pressure environment is: The simplified seawater temperature-specific heat capacity function under high temperature and high pressure environment is: f2(T)=4967-5.74468T+0.00833907*T 2 Where T is the seawater temperature, f1(T) is the density, and f2(T) is the specific heat capacity; The nozzle temperatures T1 and T2 of the first nozzle and the second nozzle are set to 370°C, then the density ρ 1exit , 2exit Both 750Kg / m 3 , the seawater bottom density ρ bottom 1039Kg / m 3 By solving the two-dimensional equation group, the source buoyancy flux B of the first nozzle and the second nozzle is obtained: 1exit , B 2exit 0.1648m respectively 4 / s 3 and 0.1176m 4 / s 3 ; The specific heat capacity C of the hot liquid in the first nozzle and the second nozzle 1p , C 2p Both are 4721 J / Kg*K, and the heat source fluxes H1 and H2 of the first nozzle and the second nozzle are 80 MW and 57 MW respectively.

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