CN110096792B - Dynamic simulation method for calculating unsteady Langmuir circulation - Google Patents

Abstract

The invention discloses a dynamic simulation method for calculating unsteady Langmuir circulation: (1) adopting nearshore ocean wave mode to calculate the wave field within a certain time range, and outputting wave parameters; (2) inputting the obtained wave parameters into Stokes drift velocity Calculation model, calculate the Stokes drift velocity; (3) Improve the Princeton ocean model, so that the Princeton ocean model includes the parametric calculation method of the unsteady Langmuir circulation; (4) Input the obtained Stokes drift velocity into the improved Princeton ocean model, real-time The ocean dynamic process including the unsteady Langmuir circulation is simulated, and the ocean temperature, salinity and current velocity fields including the influence of the physical process of the unsteady Langmuir circulation are obtained. The present invention adds the effect of unsteady langmuir circulation into the turbulent kinetic energy parameterized calculation method of the ocean circulation model, can dynamically simulate the influence of unsteady Langmuir circulation on ocean elements, can improve the physical process of the ocean numerical model, and obtain a more accurate ocean forecast model.

Description

A dynamic simulation method for calculating unsteady Langmuir circulation

Technical Field

The invention relates to a dynamic real-time simulation technology of a physical ocean model, and in particular to a dynamic simulation method for calculating an unsteady Langmuir circulation.

Background Art

Langmuir circulation refers to a pair of antisymmetric rotating vortices with axes parallel to the wind direction occurring in the upper ocean. It is one of the main manifestations of wave-current interaction. Due to the unsteady nature of the wind field on the sea surface, the unsteadiness of wind stress on the sea surface is induced, and then a vortex perpendicular to the sea surface is formed. Because the wind blows up the waves, the waves produce Stokes drift. Under the influence of Stokes drift, the vortex perpendicular to the sea surface gradually moves horizontally, and finally forms the Langmuir circulation. The existence of the Langmuir circulation enhances the vertical shear instability of the upper ocean, and directly contributes to the turbulent kinetic energy, strengthens the upper turbulent effect, and the Langmuir circulation promotes the increase of the vertical convection speed, plays the role of "entrainment", brings the heat, momentum and matter of the upper layer to a deeper position, and deepens the mixed layer of the upper ocean. Therefore, the Langmuir circulation plays a very important role in the dynamic and thermal processes of the upper ocean, and has very important significance and practical application value for the marine ecological environment and marine climate.

The intensity of the Langmuir circulation is mainly affected by the sea surface wind and wave size. Therefore, some current Langmuir circulation parameterization calculation methods that do not take into account the temporal and spatial variation characteristics of sea conditions are inaccurate, inconsistent with the actual Langmuir circulation phenomenon in the ocean, and cannot reflect the dynamic impact of the Langmuir circulation on ocean hydrological elements.

Summary of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art and provide a dynamic simulation method for calculating unsteady Langmuir circulation, add the effect of unsteady Langmuir circulation to the turbulent kinetic energy parameterization calculation method of the ocean circulation model, and improve the physical mechanism of the ocean circulation model.

The technical solution adopted by the present invention is: a dynamic simulation method for calculating unsteady Langmuir circulation, comprising the following steps:

Step 1, using the nearshore wave model to calculate the wave field within a certain time range and output wave parameters;

Step 2, inputting the wave parameters obtained in step 1 into the Stokes drift velocity calculation model to calculate the Stokes drift velocity;

Step 3, improve the Princeton Ocean Model so that it includes the parameterization calculation method of the unsteady Langmuir circulation;

Step 4, input the Stokes drift velocity obtained in step 2 into the improved Princeton ocean model in step 3, simulate the ocean dynamic process including the unsteady Langmuir circulation in real time, and obtain the ocean temperature, salinity and velocity field including the influence of the unsteady Langmuir circulation physical process, which is used to analyze the influence of the Langmuir circulation on marine materials and ocean dynamic processes.

Furthermore, in step 1, the wave parameters include: effective wave height, wavelength, wave average period and wave direction.

Furthermore, in step 2, the Stokes drift velocity calculation model is:

Where _Us is the east component of the Stokes drift velocity at a depth of z meters below the sea surface, _Vs is the north component of the Stokes drift velocity at a depth of z meters below the sea surface; | _Us (0)| is the Stokes drift velocity on the sea surface; z is the vertical coordinate; θ is the wave direction; _DS is the Stokes influence depth; _wn is the wave number; _Hs is the significant wave height; T is the average wave period; L is the wavelength; _Hs , T, L and θ are all obtained from the output of the nearshore wave model described in step 1.

Furthermore, in step 3, the improved Princeton ocean model is to add the Langmuir turbulence effect to the Mellor-Yamada 2.5-order turbulence closed model in the Princeton ocean model to obtain an improved Mellor-Yamada 2.5-order turbulence closed model.

Among them, the improved Mellor-Yamada 2.5-order turbulent closed model is:

_KMS ＝ _qlSMS (9)

是绝热衰减率修正后的密度；

是面壁近似函数；F_q是湍动能长度的水平扩散项，F_l是湍混合长度的水平扩散项；E₁，E₃，B₁，E₆，A₁和A₂是常数项；g是重力加速度；ρ₀是海水密度；

是垂向雷诺应力的东分量，由公式(7)计算得到；

是垂向湍雷诺应力的北分量，由公式(8)计算得到；K_M是垂向湍混合系数，而K_MS是和Langmuir环流有关的垂向湍混合系数；S_MS是稳定性方程，由公式(10)计算得到；G_H＝-l²q^-2N²，N是浮力频率；f_z ^s是表面函数。Wherein, q is the turbulent kinetic energy; l is the turbulent mixing length; U is the east component of the velocity, V is the north component of the velocity; _Us is the east component of the Stokes drift velocity at a depth of z meters below the sea surface, _Vs is the north component of the Stokes drift velocity at a depth of z meters below the sea surface, _Us and _Vs are calculated by the Stokes drift velocity calculation model described in step 2; x and y are horizontal coordinates, x represents the east direction, and y represents the north direction; t is the time variable; k is the generalized vertical coordinate; _sk is the thickness of the kth water layer; ω is the vertical velocity; _KH is the vertical temperature mixing coefficient, and _Kq is the vertical turbulent kinetic energy mixing coefficient;

is the density corrected for the adiabatic decay rate;

is the wall approximation function; _Fq is the horizontal diffusion term of the turbulent kinetic energy length, _Fl is the horizontal diffusion term of the turbulent mixing length; _E1 , _E3 , _B1 , _E6 , _A1 and _A2 are constant terms; g is the gravitational acceleration; _ρ0 is the seawater density;

is the east component of the vertical Reynolds stress, calculated by formula (7);

is the north component of the vertical turbulent Reynolds stress, calculated by formula (8); K _M is the vertical turbulent mixing coefficient, and K _MS is the vertical turbulent mixing coefficient related to the Langmuir circulation; S _MS is the stability equation, calculated by formula (10); G _H = -l ² q ^-2 N ² , N is the buoyancy frequency; f _z ^s is the surface function.

The beneficial effects of the present invention are as follows: the method of the present invention can dynamically simulate the influence of the unsteady Langmuir circulation on ocean elements, can improve the physical process of the ocean numerical model, and obtain a more accurate ocean forecast model, which is of great significance for studying and analyzing the exchange of matter, heat, momentum and energy and numerous physical and biochemical processes in the ocean, has a positive guiding role in constructing a marine ecological environment and disaster prediction model, realizing commercial ocean forecasting, and providing ideas and methods for disaster prevention and mitigation, provides theoretical and technical references for correctly understanding the mechanism of ocean circulation and climate change, and lays the foundation for establishing an ocean-air coupling model.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1: Schematic diagram of the simulation process of the present invention.

DETAILED DESCRIPTION

In order to further understand the content, features and effects of the present invention, the following embodiments are given as examples and described in detail with reference to the accompanying drawings:

A dynamic simulation method for calculating unsteady Langmuir circulation, comprising:

1. Nearshore Wave Model (SWAN): SWAN is the third generation of nearshore wave numerical model. It adopts the balance equation based on the principle of energy conservation and uses a fully implicit finite difference format. It is unconditionally stable and makes the computational space grid and time step unrestricted. In the source and sink terms of the balance equation, wind input, three-phase wave and four-phase wave interaction, bottom friction, wave breaking and white wave dissipation are considered. It is widely used in wave simulation under shallow water conditions. The SWAN model can output the wave parameters (effective wave height, wavelength, wave average period and wave direction, etc.) required to calculate the Stokes drift velocity.

2. Stokes drift velocity calculation model: A model for calculating Stokes drift velocity requires wave height, wavelength, period, wave direction and other wave parameter data as input. Its essence is the Stokes drift velocity calculation equation.

The Stokes drift velocity calculation model is as follows:

where _Us is the east component of the Stokes drift velocity at a depth of z meters below the sea surface, _Vs is the north component of the Stokes drift velocity at a depth of z meters below the sea surface; | _Us (0)| is the Stokes drift velocity on the sea surface; z is the vertical coordinate; θ is the wave direction; _DS is the Stokes influence depth; _wn is the wave number; _Hs is the significant wave height; T is the average wave period; L is the wavelength; _Hs , T, L and θ are all obtained from the SWAN model output.

3. Princeton Ocean Model (POM): POM is an ocean numerical model based on the three-dimensional baroclinic primitive equations. It adopts the leapfrog finite difference format and operator splitting technology and is widely used by domestic and foreign scholars in the simulation of tidal currents, wind-driven currents, mixed layers and jump layers, thermohaline circulation, ocean circulation and transport. The present invention proposes a method for improving the Mellor-Yamada 2.5-order turbulent closed model in the POM model, so that the Mellor-Yamada 2.5-order turbulent closed model includes a parameterized calculation method for calculating unsteady Langmuir circulation, specifically: adding the Langmuir turbulent effect to the Mellor-Yamada 2.5-order turbulent closed model to obtain an improved Mellor-Yamada 2.5-order turbulent closed model. The improved Mellor-Yamada 2.5-order turbulent closed model is as follows:

_KMS ＝ _qlSMS (9)

是绝热衰减率修正后的密度；

是面壁近似函数；F_q是湍动能长度的水平扩散项，F_l是湍混合长度的水平扩散项；E₁，E₃，B₁，E₆，A₁和A₂是常数项，E₁＝E₃＝1.8，B₁＝16.6，E₆＝4E₁＝7.2，A₁＝0.92，A₂＝0.74；g是重力加速度；ρ₀是海水密度；

是垂向雷诺应力的东分量，由公式(7)计算得到；

是垂向湍雷诺应力的北分量，由公式(8)计算得到；K_M是垂向湍混合系数，而K_MS是和Langmuir环流有关的垂向湍混合系数；S_MS是稳定性方程，由公式(10)计算得到；G_H＝-l²q^-2N²，N是浮力频率；f_z ^s是表面函数。Wherein, q is the turbulent kinetic energy; l is the turbulent mixing length; U is the east component of the velocity, V is the north component of the velocity; _Us is the east component of the Stokes drift velocity at a depth of z meters below the sea surface, _Vs is the north component of the Stokes drift velocity at a depth of z meters below the sea surface, _Us and _Vs are calculated by the Stokes drift velocity calculation model described in step 2; x and y are horizontal coordinates, x represents the east direction, and y represents the north direction; t is the time variable; k is the generalized vertical coordinate; _sk is the thickness of the kth water layer; ω is the vertical velocity; _KH is the vertical temperature mixing coefficient, and _Kq is the vertical turbulent kinetic energy mixing coefficient;

is the density corrected for the adiabatic decay rate;

is the wall approximation function; _Fq is the horizontal diffusion term of the turbulent kinetic energy length, _Fl is the horizontal diffusion term of the turbulent mixing length; _E1 , _E3 , _B1 , _E6 , _A1 and _A2 are constant terms, _E1 = _E3 = 1.8, _B1 = 16.6, _E6 = 4E1 = _7.2 , _A1 = 0.92, _A2 = 0.74; g is the gravitational acceleration; _ρ0 is the seawater density;

is the east component of the vertical Reynolds stress, calculated by formula (7);

is the north component of the vertical turbulent Reynolds stress, calculated by formula (8); K _M is the vertical turbulent mixing coefficient, and K _MS is the vertical turbulent mixing coefficient related to the Langmuir circulation; S _MS is the stability equation, calculated by formula (10); G _H = -l ² q ^-2 N ² , N is the buoyancy frequency; f _z ^s is the surface function.

The present invention uses the SWAN model to calculate the wave field within a certain time range, outputs wave parameters, and passes the wave parameters to the Stokes drift velocity calculation model to calculate the Stokes drift velocity. Then, the parameterized calculation method of the unsteady Langmuir circulation is introduced into the POM model to obtain the improved POM model. Finally, the obtained Stokes drift velocity is used to simulate the ocean dynamic process including the unsteady Langmuir circulation in real time using the improved POM model, and the ocean temperature, salinity and velocity field including the influence of the unsteady Langmuir circulation physical process are obtained, which is used to analyze the influence of the Langmuir circulation on the marine material and the marine dynamic process.

As shown in Figure 1, the operation process of the present invention is as follows:

①: SWAN mode starts running, calculates the wave field within a certain period of time, outputs the wave parameter data file, and terminates the operation.

②: The Stokes drift velocity calculation model receives the wave parameter data file, starts running, calculates the Stokes drift velocity field, and terminates after outputting the data file.

③: Improve the POM model to include the parameterized calculation method of unsteady Langmuir circulation.

④: After the improved POM mode receives the Stokes drift velocity file, it starts running, simulates the ocean dynamic process including the unsteady Langmuir circulation in real time, and terminates the operation after outputting the ocean hydrological element data (ocean hydrological element data includes ocean temperature, salinity and velocity field, etc.) file.

When the POM operation is completed, the output ocean hydrological element data reflects the influence of the Langmuir circulation on the ocean circulation process. Compared with not considering the Langmuir circulation process or only considering the steady Langmuir circulation process, the present invention is more in line with the physical process occurring in the actual ocean, reflects the dynamic influence of the Langmuir circulation on the ocean, can improve the physical mechanism of the ocean numerical model, and obtain a more accurate ocean forecast model, which is of great significance for the study and analysis of the exchange of matter, heat, momentum and energy in the ocean and numerous physical and biochemical processes.

Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments. The above-mentioned specific embodiments are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, which all fall within the scope of protection of the present invention.

Claims (3)

1. A dynamic simulation method for calculating unsteady Langmuir circulating current is characterized by comprising the following steps:

step 1, calculating a wave field within a certain time range by adopting an offshore wave mode, and outputting wave parameters;

step 2, inputting the wave parameters obtained in the step 1 into a Stokes drift velocity calculation model, and calculating to obtain a Stokes drift velocity;

step 3, improving the Princeton ocean mode to enable the Princeton ocean mode to comprise a parametric calculation method of unsteady Langmuir circulation;

the improved Princeton ocean model is obtained by adding a Langmuir turbulence effect to a Mellor-Yamada2.5 order turbulence closed model in the Princeton ocean model, and the improved Mellor-Yamada2.5 order turbulence closed model is as follows:

K _MS ＝qlS _MS (9)

wherein q is turbulent kinetic energy; l is the turbulent mixing length; u is the east component of the flow velocity and V is the north component of the flow velocity; u shape _s Is the east component of the stokes drift velocity, V, at a depth z meters below the sea surface _s Is the north component, U, of the stokes drift velocity at a depth of z meters below the sea surface _s And V _s Calculating by the Stokes drift velocity calculation model in the step 2; x and y are horizontal coordinates, x represents the east direction and y represents the north direction; t is a time variable; k is a generalized vertical coordinate; s _k Is the thickness of the k-th aqueous layer; ω is the vertical flow rate; k _H Is the vertical temperature mixing coefficient, K _q Is the vertical turbulence kinetic energy mixing coefficient;

is the density after adiabatic decay rate correction;

Is a face-wall approximation function; f _q Is a horizontal diffusion term of the length of the turbulent kinetic energy, F _l A horizontal diffusion term that is the turbulent mixing length; e ₁ ，E ₃ ，B ₁ ，E ₆ ，A ₁ And A ₂ Is a constant term; g is the acceleration of gravity; rho ₀ Is the seawater density;

Is the east component of the vertical reynolds stress, which is calculated by the formula (7);

The north component of the vertical turbulent Reynolds stress is obtained by calculation according to a formula (8); k _M Is vertical turbulent mixingCoefficient, and K _MS Is the vertical turbulent mixing coefficient associated with Langmuir circulating currents; s. the _MS Is a stability equation calculated from equation (10); g _H ＝-l ² q ^-2 N ² N is the buoyancy frequency; f. of _z ^s Is a surface function;

and 4, inputting the stokes drift velocity obtained in the step 2 into the Princeton ocean mode improved in the step 3, simulating an ocean dynamic process containing unsteady Langmuir circulation in real time, obtaining an ocean temperature, salinity and flow velocity field containing unsteady Langmuir circulation physical process influence, and analyzing the influence of the Langmuir circulation on ocean substances and an ocean power process.

2. A dynamic simulation method for calculating unsteady Langmuir circulating currents as claimed in claim 1, wherein in step 1, said wave parameters comprise: effective wave height, wavelength, wave mean period and wave direction.

3. The dynamic simulation method for calculating a unsteady Langmuir circulating current according to claim 1, wherein in the step 2, the Stokes shift velocity calculation model is:

in the formula of U _s Is the east component of the stokes drift velocity, V, at a depth z meters below the sea surface _s Is the north component of the stokes drift velocity at a depth z meters below the sea surface; | U _s (0) L is the stokes drift velocity at the sea surface; z is a vertical coordinate; θ is the wave direction; d _S Is stokes depth of influence; w is a _n Is the wave number; h _s Is the effective wave height; t is the wave mean period; l is a wavelength; h _s T, L and theta are all obtained by the near-shore wave mode output in the step 1.

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