A temperature difference density flow control device and method for improving lake bottom hypoxia

Abstract

The present invention discloses a temperature-difference gravity flow control device and method for improving oxygen deficiency at the bottom layer of a lake or reservoir, comprising an unmanned boat arranged on the water surface, the unmanned boat being provided with a bottom-penetrating sonar for measuring underwater topography, the unmanned boat being provided with a liftable multi-parameter water quality sensor, a water outlet and a water suction port, the water suction port being connected to one end of a water pump in the cabin through a hose, the other end of the water pump being connected to an aerator inlet through a pipe, the aerator outlet being connected to a refrigerator inlet through a pipe, and the refrigerator outlet being connected to the water outlet through a hose; the present invention fully utilizes the temperature-difference gravity flow to increase the dissolved oxygen concentration in the bottom environment of a lake or reservoir.

Description

Technical Field

[0001] The present invention relates to the technical field of temperature differential density flow control, and in particular to a temperature differential density flow control device and method for improving hypoxia at the bottom of a lake or reservoir. Background Art

[0002] Dissolved oxygen is the most important element in the aquatic environment, besides water itself, and plays a vital role in water quality safety and the health of the aquatic ecosystem. However, the water temperature stratification common in deepwater lakes and reservoirs often prevents the oxygen-rich surface water from replenishing dissolved oxygen to the bottom water. At the same time, the pollutant-rich water and sediments at the bottom are hot spots for dissolved oxygen consumption. Therefore, the bottom environment of deepwater lakes and reservoirs is often hypoxic. Under hypoxic conditions, sediments will release substances such as methane and nitrous oxide, which have a stronger greenhouse effect, thereby increasing carbon emissions from the lake environment. On the other hand, they will also produce reducing substances that are more harmful to the water environment, promoting the formation of black and smelly water bodies and causing devastating damage to the lake and reservoir ecosystem. In particular, for lakes and reservoirs that undertake important water supply tasks, the water supply for urban residents will be threatened.

[0003] Currently, methods for improving hypoxia in the bottom layers of lakes and reservoirs primarily include disrupting water stratification, deep-water aeration, and chemical oxygenation. Disrupting water stratification involves lifting hypoxic bottom water to the surface through air plume mixing or bucket mixing, while transporting surface water with high dissolved oxygen to the bottom. Deep aeration oxygenates only the hypoxic bottom water without promoting mixing of the surface and bottom waters or disrupting water temperature stratification. Chemical oxygenation involves introducing high-oxygen compounds into the bottom water or sediment to supplement the oxygen required for organic matter decomposition. However, these methods can only improve hypoxia within a limited area of ​​a lake or reservoir and are unlikely to comprehensively improve dissolved oxygen conditions throughout the bottom layer. Some methods also have potential negative impacts. For example, disrupting water stratification may bring highly polluted bottom water to the surface, exacerbating water quality deterioration. Chemical oxygenation can significantly impact benthic habitats, altering the chemical composition of sediments, and has low public acceptance.

[0004] Hyperpycnal flow refers to the stratified flow phenomenon that occurs when two fluids with significantly different densities meet in an aquatic environment. Current research on hyperpycnal flow in lakes and reservoirs primarily focuses on sediment hyperpycnal flow, where incoming water with high sediment content, due to its higher density, flows along the bottom of lakes and reservoirs. Sediment hyperpycnal flow regulation through the coordinated operation of cascade reservoirs has become a key method for water and sediment regulation in my country's Yellow River. Thermal hyperpycnal flow, where incoming water with relatively low temperature and high density moves along the bottom of lakes and reservoirs, has been observed in lakes and reservoirs worldwide in recent years. Thermal hyperpycnal flow is often fully exposed to air and oxygenated before descending. Furthermore, because dissolved oxygen has a higher solubility in low-temperature water, thermal hyperpycnal flow typically produces oxygen-rich water, offering significant potential for alleviating hypoxia in lakes and reservoirs. Compared to existing hypoxia mitigation methods, thermal hyperpycnal flow can affect a wider area, thus alleviating hypoxia overall. Furthermore, as a natural phenomenon, thermal hyperpycnal flow does not require the significant energy required by traditional aeration methods, making it an economical and environmentally friendly method for mitigating hypoxia in lakes and reservoirs.

[0005] Although using temperature-difference gravity currents to oxygenate the bottom environment of lakes and reservoirs has the above-mentioned advantages, the movement characteristics of naturally occurring temperature-difference gravity currents, such as the entry point and diving depth, are significantly affected by the regional topography, which may lead to obstruction of their diving process or limited diving distance, thus failing to fully realize their potential to oxygenate the bottom environment of lakes and reservoirs. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a temperature-difference density flow control device and method for improving the hypoxia at the bottom of lakes and reservoirs. The movement form of the temperature-difference density flow is improved by temperature regulation, its diving distance is increased and it is induced to move to the key oxygen increase area. At the same time, aeration measures are combined to enhance the oxygen carrying capacity of the temperature-difference density flow to avoid the depletion of the dissolved oxygen it carries before the density flow stops moving, thereby making full use of the temperature-difference density flow to increase the dissolved oxygen concentration in the bottom environment of lakes and reservoirs.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a temperature difference gravity flow control device for improving the hypoxia at the bottom of a lake reservoir, including an unmanned boat arranged on the water surface, the unmanned boat is provided with a bottom-penetrating sonar for measuring underwater topography, the unmanned boat is provided with a liftable multi-parameter water quality sensor, a water outlet and a water suction port, the water suction port is connected to one end of the water pump in the cabin through a hose, the other end of the water pump is connected to the aerator inlet through a pipe, the aerator outlet is connected to the refrigerator inlet through a pipe, and the refrigerator outlet is connected to the water outlet through a hose.

[0008] Preferably, the multi-parameter water quality sensor, water outlet and water suction port are respectively connected to corresponding hoisting devices.

[0009] Preferably, the multi-parameter water quality sensor is connected to the first reel through a rope, and the input end of the first reel is connected to the output end of the first winch motor; the water outlet is connected to the second reel through a rope, and the input end of the second reel is connected to the output end of the second winch motor; the water pumping port is connected to the third reel through a rope, and the input end of the third reel is connected to the output end of the third winch motor.

[0010] Preferably, the signal output ends of the bottom-penetrating sonar and the multi-parameter water quality sensor are both connected to the controller input end, and the controller output end is respectively connected to the water pump, aerator, refrigerator, and winch control end.

[0011] Preferably, a solar photovoltaic panel is provided on the upper side of the unmanned boat, the output end of the solar photovoltaic panel is connected to the input end of the battery, and a propeller propulsion device is provided on the rear side of the unmanned boat.

[0012] In addition, the present invention also discloses a control method of the temperature-difference density flow control device for improving hypoxia at the bottom of a lake or reservoir, which comprises the following steps:

[0013] Step 1: Control the entry point of the temperature-density flow: Find the entry point of the temperature-density flow and perform control at the entry point to optimize the movement process of the density flow and increase its initial oxygen carrying capacity;

[0014] Step 2: Control the relay points of the temperature-difference gravity flow: The relay points are where the temperature-difference gravity flow is about to stop moving or the dissolved oxygen it carries is about to be exhausted. Find the relay points of the temperature-difference gravity flow and carry out control at the relay points to continue the movement of the temperature-difference gravity flow and replenish the dissolved oxygen it carries, so that it can continue to move and replenish the dissolved oxygen at the bottom of the lake.

[0015] Furthermore, the Step 1 is specifically as follows:

[0016] Step 1.1: Remotely control the unmanned boat from the downstream to the upstream of the lake to conduct underway observations. Pause after sailing continuously for 2% of the total length of the lake. Use bottom-penetrating sonar to measure the water depth at the pause point. Use the first winch motor to drive a multi-parameter water quality sensor from the water surface to the bottom at a uniform speed of no more than 0.25 m / s. During this time, collect water temperature data at a frequency of no less than 1 Hz to obtain a vertical water temperature profile.

[0017] Step 1.2: The vertical temperature gradient is derived from the vertical depth to identify the water temperature structure. Areas with a water temperature gradient of at least 2°C / m are designated as thermoclines. If only one thermocline is identified at a pause point during the underway observation, this indicates no temperature gradient intrusion, which is considered Stage I. If two thermoclines are identified at a pause point, with a vertical spacing of at least 2 m, this indicates the presence of temperature gradient intrusion, which is considered Stage II. If no thermocline is identified at a pause point, meaning the maximum vertical temperature gradient is less than 2°C / m, this indicates the unmanned vessel has reached the river channel of the lake or reservoir, which is considered Stage III.

[0018] Step 1.3: Determine the entry point of the temperature-density current. The spatial critical point where stage III transitions to stage II is the entry point of the temperature-density current. To accurately locate the entry point through underway observation, the unmanned vessel should sail upstream of the lake in both states I and II, and downstream of the lake in state III. This binary method is then used to determine the location of the entry point of the temperature-density current.

[0019] Step 1.4: Control the entry point of the temperature-density flow. The unmanned boat is directed to the entry point of the temperature-density flow and pauses. The water depth at the entry point is measured by a bottom-penetrating sonar. The multi-parameter water quality sensor is then driven by the first winch motor to hover at a height of 1 m above the riverbed, continuously monitoring the water temperature and dissolved oxygen concentration of the temperature-density flow. At the same time, the third winch motor and the second winch motor respectively control the water inlet and outlet to be lowered to a height of 1 m above the riverbed. m height and suspended to prevent the temperature-difference gravity flow control measures from disturbing the sediment; then, the water is pumped into the aerator for oxygenation treatment to adjust the oxygen carrying capacity of the temperature-difference gravity flow, and then into the refrigerator for cooling treatment to adjust the movement capacity of the temperature-difference gravity flow; real-time monitoring of the multi-parameter water quality sensor reflects the temperature-difference gravity flow control effect. When the water temperature recorded by the multi-parameter water quality sensor is consistent with the bottom water temperature in stage I, the movement characteristics of the entry point of the temperature-difference gravity flow are controlled; when the dissolved oxygen concentration recorded by the water quality sensor is consistent with the saturated dissolved oxygen concentration corresponding to the water flow temperature, the oxygen carrying characteristics of the entry point of the temperature-difference gravity flow are controlled;

[0020] Step 1.5: Once the temperature-density current's movement characteristics are adjusted, its entry point and depth will also change accordingly. Repeat Steps 1.3-1.4 repeatedly to confirm that the temperature-density current's entry movement and oxygen-carrying characteristics are adjusted to a more ideal state.

[0021] Furthermore, the Step 2 is specifically as follows:

[0022] Step 2.1: Determine the relay point of the temperature-gravity current. The water temperature relay point and dissolved oxygen relay point of the temperature-gravity current may not coincide and need to be explored separately. The water temperature relay point is the spatial critical point where stage II transitions to stage I as described in Step 1.2. To determine the water temperature relay point through underway observation, the unmanned vessel is instructed to sail upstream of the lake in state I and downstream of the lake in state II. The water temperature relay point of the temperature-gravity current is finally determined through a binary method. When the unmanned vessel conducts aerial surveys between the entry point of the temperature-gravity current and the movement relay point, if the measured dissolved oxygen concentration at the bottom of the lake is less than 2 mg / L, it indicates that the dissolved oxygen carried by the temperature-gravity current has almost been replenished to the bottom water body, and therefore the area is marked as the dissolved oxygen relay point of the temperature-gravity current.

[0023] Step 2.2: Conduct temperature relay regulation of the temperature-difference gravity flow. The unmanned boat is directed to sail to the temperature relay point of the temperature-difference gravity flow and pause, while the water depth at the entry point is measured using a bottom-penetrating sonar. The multi-parameter water quality sensor is then driven vertically by the first winch motor to analyze the vertical water temperature structure changes in the area according to Step 1.2. Simultaneously, the third and second winch motors control the water inlet and outlet, respectively, to be lowered to a height of 1 m above the riverbed and suspended. A water pump is then used to pump the bottom water into a refrigerator for cooling before returning it to the bottom of the lake, thus continuing the temperature-difference gravity flow process. When the real-time monitoring results of the multi-parameter water quality sensor indicate that the aforementioned regulation has caused the area to transition from Stage I to Stage II, the temperature relay regulation of the temperature-difference gravity flow is complete.

[0024] Step 2.3: Carry out dissolved oxygen relay regulation of the temperature-difference gravity flow; have the unmanned boat sail to the dissolved oxygen relay point of the temperature-difference gravity flow and pause, and use the bottom-penetrating sonar to measure the water depth at the entry point; then, the first winch motor drives the multi-parameter water quality sensor to move to a height of 1 m above the riverbed and hover, continuously monitoring the dissolved oxygen concentration of the bottom water; at the same time, the third winch motor and the second winch motor respectively control the water inlet and outlet to be lowered to a height of 1 m above the riverbed and suspended, and then the bottom water is pumped into the aerator for oxygenation and then transported back to the bottom of the lake reservoir, so that the temperature-difference gravity flow can carry more dissolved oxygen to alleviate the hypoxia phenomenon at the bottom of the lake reservoir; when the real-time monitoring results of the multi-parameter water quality sensor indicate that the above-mentioned control has made the dissolved oxygen concentration of the temperature-difference gravity flow close to saturation, the dissolved oxygen relay regulation of the temperature-difference gravity flow is completed.

[0025] Beneficial effects of the present invention:

[0026] (1) Most existing oxygenation technologies can only increase oxygen in a small area at the bottom of lakes and reservoirs with huge energy consumption. The present invention aims to regulate the naturally occurring temperature-density flow, so as to use the natural trend to transport dissolved oxygen to the bottom area of ​​lakes and reservoirs along the way. Therefore, it is possible to achieve a large-scale improvement in dissolved oxygen environment with less energy loss. The present invention improves the movement form of the temperature-density flow by temperature regulation, increases its diving distance and induces it to move to the key oxygenation area. At the same time, it combines aeration measures to enhance the oxygen carrying capacity of the temperature-density flow, and avoids the dissolved oxygen it carries being exhausted before the movement of the density flow stops, thereby making full use of the temperature-density flow to increase the dissolved oxygen concentration in the bottom environment of lakes and reservoirs.

[0027] (2) The present invention tracks the entire life cycle of the temperature-difference density current from its formation to its dissipation, and then combines cooling and oxygenation measures to regulate the movement state and oxygen-carrying state of the density current, so that it has a longer range and oxygenation benefit compared with the natural density current; at the same time, the present invention aims to coordinate the movement state and oxygen-carrying state of the density current through regulation, so that the potential of the temperature-difference density current to improve the hypoxia at the bottom of the lake reservoir can be fully utilized.

[0028] (3) The present invention avoids direct aeration of the bottom water by pumping it into an unmanned boat for treatment and then returning it to its original water layer, thus not causing significant interference with the bottom sediments. At the same time, the flow rate of the temperature difference gravity flow itself is relatively small, which will not cause the resuspension of the sediments. Therefore, the present invention effectively avoids the risk of disturbing the sediments during the oxygenation process at the bottom of the lake and reservoir, causing the accumulated pollutants to be released into the water.

[0029] (4) The present invention tracks the formation and movement of temperature-difference gravity currents by underway observation combined with vertical measurement using a winch to pull a multi-parameter water quality sensor, and analyzes their ability to replenish dissolved oxygen in the bottom area of ​​the lake.

[0030] (5) The present invention extracts water from a designated water layer into the unmanned cabin for cooling and oxygenation treatment, thereby regulating the movement state and oxygen-carrying state of the temperature-difference density flow, and ultimately utilizing the temperature-difference density flow to fully alleviate the hypoxia phenomenon at the bottom of the lake.

[0031] (6) The present invention adopts two methods of entry point control and relay point control for the temperature-difference density flow, intervening at the point where the density flow is formed and at the time when it dissipates, respectively, so that the controlled temperature-difference density flow has a longer travel distance than the natural temperature-difference density flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the structure of a temperature difference density flow control device for improving the hypoxia at the bottom of a lake or reservoir;

[0033] Figure 2Schematic diagram of the infiltration and dissipation characteristics of temperature difference gravity flow;

[0034] Figure 3 Schematic diagram of the steps for regulating the entry point of temperature-difference gravity flow;

[0035] Figure 4 Schematic diagram of vertical water temperature characteristics in different movement stages of temperature-difference gravity flow;

[0036] Figure 5 Schematic diagram of the relay point control steps for temperature difference gravity flow;

[0037] Figure 6 Schematic diagram of the relay regulation characteristics of water temperature and dissolved oxygen in temperature-differential gravity flow. DETAILED DESCRIPTION

[0038] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

[0039] like Figure 1 As shown, a temperature difference gravity flow control device for improving hypoxia at the bottom of a lake or reservoir comprises an unmanned boat arranged on the water surface, the unmanned boat being provided with a bottom-penetrating sonar 1 for measuring underwater topography, the unmanned boat being provided with a liftable multi-parameter water quality sensor 3, a water outlet 5-1 and a water suction port 5-2, the water suction port 5-2 being connected to one end of a water pump 7 in the cabin through a hose 6, the other end of the water pump 7 being connected to the inlet of an aerator 8 through a pipe, the outlet of the aerator 8 being connected to the inlet of a refrigerator 9 through a pipe, and the outlet of the refrigerator 9 being connected to the water outlet 5-1 through a hose 6.

[0040] Preferably, the multi-parameter water quality sensor 3, the water outlet 5-1 and the water suction port 5-2 are respectively connected to corresponding hoisting devices.

[0041] Preferably, the multi-parameter water quality sensor 3 is connected to the first reel 4-1 through a rope, and the input end of the first reel 4-1 is connected to the output end of the first hoisting motor 2-1; the water outlet 5-1 is connected to the second reel 4-2 through a rope, and the input end of the second reel 4-2 is connected to the output end of the second hoisting motor 2-2; the water pumping port 5-2 is connected to the third reel 4-3 through a rope, and the input end of the third reel 4-3 is connected to the output end of the third hoisting motor 2-3.

[0042] Preferably, the signal output ends of the bottom-penetrating sonar 1 and the multi-parameter water quality sensor 3 are both connected to the input end of the controller 11, and the output end of the controller 11 is respectively connected to the water pump 7, the aerator 8, the refrigerator 9, and the winch control end.

[0043] Preferably, a solar photovoltaic panel 10 is provided on the upper side of the unmanned boat, the output end of the solar photovoltaic panel 10 is connected to the input end of the battery, and a propeller propulsion device 12 is provided on the rear side of the unmanned boat.

[0044] In this embodiment, water drawn in through intake port 5-2 is primarily oxygenated by aerator 8 and cooled by refrigerator 9 within the cabin. Power consumption for these devices is provided by solar photovoltaic panels 10, with instructions issued by controller 11. Note that the water flows through aerator 8 before passing through refrigerator 9. This is because the water heats up to a certain degree when it comes into contact with air and is aerated. Cooling after aeration can offset this warming effect. Conversely, cooling before aeration, or connecting the refrigerator and aerator in parallel, cannot achieve this beneficial effect.

[0045] Generally speaking, the device can be divided into an aerial survey module, a bottom-probing module, a density current tracking module, and a density current control module. The aerial survey module is primarily implemented using an unmanned boat and its power system; the bottom-probing module is primarily implemented using sonar; the density current tracking module is primarily implemented using a winch to drive a multi-parameter water quality sensor for vertical observation, used to explore the development and evolution of temperature-density currents and the simultaneous changes in dissolved oxygen concentration they carry; the density current control module primarily uses a winch and water pump to extract water from a specified water layer, and then returns it to the original water layer through an aerator and refrigerator to control the movement state and oxygen-carrying characteristics of the temperature-density current.

[0046] The device designed by the present invention can regulate the water temperature and dissolved oxygen concentration of the temperature-difference gravity flow by cooling and oxygenating, and the regulation methods include immersion point regulation and relay point regulation. Figure 2 As shown in the figure, when the low-temperature inflow enters the lake from upstream, it will dive at entry point 14 and move along the bottom of the lake, forming a temperature-gravity current. The water depth at the entry point is called the entry point depth 13. The temperature-gravity current moves relatively independently from the upper water flow, separated by a dividing line 15. However, as it moves, it will mix with the original water in the lake, causing its temperature to rise and eventually approach the temperature of the lake bottom, at which point the temperature-gravity current dissipates.

[0047] The motion characteristics of the temperature difference density flow satisfy the following formula

[0048]

[0049] in F p is the density Froude number, g is the acceleration due to gravity, ρ is the water density, all three can be considered as constants, so their product is also a constant; h p is the water depth at the entry point, Δ ρ is the density difference between the hyperpycnal current and the upper water body, u pis the flow velocity of the density flow, and there is a functional relationship between the three. Therefore, the temperature of the temperature-differential density flow, that is, the density difference between it and the upper water body, can be changed by the device constructed by the present invention to change the movement state of the density flow. On the one hand, the appropriate entry point position or the depth of the entry point has a key influence on its subsequent travel distance; at the entry point of the temperature-differential density flow, the flow velocity can be regarded as a constant value, so cooling the density flow water body and increasing the density difference between it and the lake water body can reduce the diving depth, that is, the temperature-differential density flow dives earlier. On the other hand, the temperature difference of the temperature-differential density flow gradually dissipates during its travel, and the movement gradually stops. At this time, it can be relayed to extend its movement distance; from the formula, at the relay point of the temperature-differential density flow, the water depth of the entry point can be regarded as a constant value, so cooling the density flow water body and increasing the density difference between it and the lake water body can increase the movement speed, that is, the travel distance of the temperature-differential density flow becomes longer.

[0050] The present invention utilizes temperature-differential gravity flow to improve hypoxia in the lake bottom. Specifically, the temperature-differential gravity flow releases the dissolved oxygen it carries into the surrounding waters of the lake during its movement. Therefore, in addition to the movement of the temperature-differential gravity flow, i.e., the dissipation of the temperature difference, it is also important to consider its oxygen replenishment process, i.e., the dissipation of the dissolved oxygen difference. Obviously, the ideal situation is that when the temperature-differential gravity flow dissipates, the dissolved oxygen it carries has also been completely replenished to the surrounding waters. At this point, the temperature-differential gravity flow can achieve its optimal dissolved oxygen replenishment effect on the bottom water. The suboptimal situation is that when the temperature-differential gravity flow stops moving, the dissolved oxygen it carries remains. In this case, the area where the gravity flow dissipates receives a large amount of dissolved oxygen, but it cannot benefit a wider area. The undesirable situation is that the dissolved oxygen it carries is exhausted before the temperature-differential gravity flow stops moving. In this case, the oxygen replenishment effect of the gravity flow is significantly limited. The present invention adjusts the oxygen-carrying characteristics of the temperature-differential gravity flow through aeration devices, so that the dissolved oxygen dissipation process matches the dissipation process of the temperature difference, thereby fully utilizing the temperature-differential gravity flow's ability to improve the dissolved oxygen environment in the lake bottom.

[0051] Specifically, the present invention discloses a control method for the temperature-difference density flow control device for improving hypoxia at the bottom of a lake or reservoir, which comprises the following steps:

[0052] Step 1: Control the entry point of temperature difference gravity flow as follows Figure 3-4 ; Find the entry point of the temperature-density current and carry out regulation at the entry point, so as to optimize the movement process of the density current and increase its initial oxygen carrying capacity; the temperature-density current regulated by the entry point has a longer diving distance and better dissolved oxygen replenishment capacity, which can better improve the hypoxia situation at the bottom of the lake.

[0053] Step 1.1: Use remote commands to control the unmanned boat to sail from the downstream of the lake to the upstream, conducting underway observations. After sailing continuously for 2% of the total length of the lake, the boat pauses and measures the water depth at the pause point using a bottom-penetrating sonar 1. The multi-parameter water quality sensor 3 is driven by the first winch motor 2-1 to be lowered from the water surface to the bottom at a uniform speed of no more than 0.25 m / s. During this time, water temperature data is collected at a frequency of no less than 1 Hz to obtain a vertical water temperature profile.

[0054] Step 1.2: Derivative the vertical water temperature with respect to the vertical water depth to obtain the vertical change of the water temperature gradient, and then identify the water temperature structure; the area with a water temperature gradient of not less than 2°C / m is recorded as a thermocline. If only one thermocline is identified at a pause point during the cruise observation, it indicates that there is no temperature difference intrusion in the area. Figure 3-4 If two thermoclines are identified at a pause point and the vertical distance between the two thermoclines is not less than 2 m, it indicates that there is a temperature difference intrusion phenomenon in the area. Figure 3-4 If no thermocline is identified at a pause point, that is, the maximum vertical water temperature gradient is less than 2°C / m, it means that the unmanned vessel has sailed to the river section of the lake. Figure 3-4 The middle is labeled as stage III;

[0055] Step 1.3: Determine the entry point of the temperature-density current. The spatial critical point where stage III transitions to stage II is the entry point of the temperature-density current. To accurately locate the entry point through underway observation, the unmanned vessel should sail upstream of the lake in both states I and II, and downstream of the lake in state III. This binary method is then used to determine the location of the entry point of the temperature-density current.

[0056] Step 1.4: Control the entry point of the temperature-density flow. The unmanned boat is directed to the entry point of the temperature-density flow and pauses. The bottom-penetrating sonar 1 measures the water depth at the entry point. The multi-parameter water quality sensor 3 is then driven by the first winch motor 2-1 to hover at a height of 1 m above the riverbed, continuously monitoring the water temperature and dissolved oxygen concentration of the temperature-density flow. At the same time, the third winch motor 2-3 and the second winch motor 2-2 respectively control the water inlet 5-2 and the water outlet 5-1 to be lowered to a height of 1 m above the riverbed. m height and suspended to avoid the temperature difference gravity flow control measures disturbing the sediment; then, the water is pumped by the water pump 7 to the aerator 8 for oxygenation treatment to adjust the oxygen carrying capacity of the temperature difference gravity flow, and then to the refrigerator 9 for cooling treatment to adjust the movement capacity of the temperature difference gravity flow; the real-time monitoring of the multi-parameter water quality sensor 3 reflects the temperature difference gravity flow control effect. When the water temperature recorded by the multi-parameter water quality sensor 3 is consistent with the bottom water temperature of stage I, the movement characteristic control of the entry point of the temperature difference gravity flow is completed; when the dissolved oxygen concentration recorded by the water quality sensor is consistent with the saturated dissolved oxygen concentration corresponding to the water flow temperature, the oxygen carrying characteristic control of the entry point of the temperature difference gravity flow is completed;

[0057] Step 1.5: Once the temperature-density current's movement characteristics are adjusted, its entry point and depth will also change accordingly. Repeat Steps 1.3-1.4 repeatedly to confirm that the temperature-density current's entry movement and oxygen-carrying characteristics are adjusted to a more ideal state.

[0058] Step 2: Control the relay point of temperature difference reflow as follows Figures 5 and 6 : The relay point is the place where the temperature-difference gravity current is about to stop moving or the dissolved oxygen it carries is about to be exhausted. We need to find the relay point of the temperature-difference gravity current and carry out regulation at the relay point to continue the movement of the temperature-difference gravity current and replenish the dissolved oxygen it carries, so that it can continue to move and replenish the dissolved oxygen at the bottom of the lake.

[0059] Step 2.1: Determine the relay point of the temperature-gravity current. The water temperature relay point and dissolved oxygen relay point of the temperature-gravity current may not coincide and need to be explored separately. The water temperature relay point is the spatial critical point where stage II transitions to stage I as described in Step 1.2. To determine the water temperature relay point through underway observation, the unmanned vessel is instructed to sail upstream of the lake in state I and downstream of the lake in state II. The water temperature relay point of the temperature-gravity current is finally determined through a binary method. When the unmanned vessel conducts aerial surveys between the entry point of the temperature-gravity current and the movement relay point, if the measured dissolved oxygen concentration at the bottom of the lake is less than 2 mg / L, it indicates that the dissolved oxygen carried by the temperature-gravity current has almost been replenished to the bottom water body, and therefore the area is marked as the dissolved oxygen relay point of the temperature-gravity current.

[0060] Step 2.2: Conduct water temperature relay regulation of the temperature-difference gravity flow; direct the unmanned boat to the temperature relay point of the temperature-difference gravity flow and pause, while the bottom-penetrating sonar 1 measures the water depth at the entry point; then, the first hoisting motor 2-1 drives the multi-parameter water quality sensor 3 to continuously move vertically, and analyze the vertical water temperature structure changes in the area according to Step 1.2; simultaneously, the third hoisting motor 2-3 and the second hoisting motor 2-2 respectively control the water inlet 5-2 and the water outlet 5-1 to be lowered to a height of 1 m from the riverbed and suspended, and then the bottom water is pumped by the water pump 7 to the refrigerator 9 for cooling and then transported back to the bottom of the lake reservoir, thereby continuing the movement process of the temperature-difference gravity flow; when the real-time monitoring results of the multi-parameter water quality sensor 3 indicate that the above-mentioned regulation has caused the area to transition from stage I to stage II, the water temperature relay regulation of the temperature-difference gravity flow is completed;

[0061] Step 2.3: Carry out dissolved oxygen relay regulation of the temperature-difference gravity flow; the unmanned boat is directed to sail to the dissolved oxygen relay point of the temperature-difference gravity flow and pause, and the water depth at the diving point is measured by the bottom-penetrating sonar 1; the multi-parameter water quality sensor 3 is then driven by the first winch motor 2-1 to move to a height of 1 m above the riverbed and hover, continuously monitoring the dissolved oxygen concentration of the bottom water; at the same time, the third winch motor 2-3 and the second winch motor 2-2 respectively control the water inlet 5-2 and the water outlet 5-1 to be lowered to a height of 1 m above the riverbed and suspended, and then the bottom water is pumped by the water pump 7 to the aerator 8 for oxygenation and then transported back to the bottom of the lake reservoir, so that the temperature-difference gravity flow can carry more dissolved oxygen to alleviate the hypoxia phenomenon at the bottom of the lake reservoir; when the real-time monitoring results of the multi-parameter water quality sensor 3 indicate that the above-mentioned control has made the dissolved oxygen concentration of the temperature-difference gravity flow close to saturation, the dissolved oxygen relay regulation of the temperature-difference gravity flow is completed.

[0062] The above embodiments are merely preferred technical solutions of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention shall be the technical solutions set forth in the claims, including equivalent alternatives to the technical features of the technical solutions set forth in the claims. In other words, equivalent alternatives and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A control method for a temperature-difference density flow control device for improving hypoxia at the bottom of a lake or reservoir, the temperature-difference density flow control device for improving hypoxia at the bottom of a lake or reservoir comprising an unmanned boat arranged on the water surface, the unmanned boat being provided with a bottom-penetrating sonar (1) for measuring underwater topography, the unmanned boat being provided with a liftable multi-parameter water quality sensor (3), a water outlet (5-1) and a water pumping port (5-2), the water pumping port (5-2) being connected to one end of a water pump (7) in the cabin through a hose (6), the other end of the water pump (7) being connected to an inlet of an aerator (8) through a pipe, the outlet of the aerator (8) being connected to an inlet of a refrigerator (9) through a pipe, and the outlet of the refrigerator (9) being connected to the water outlet (5-1) through a hose (6); characterized in that: It includes the following steps: Step 1: Control the entry point of the temperature-density flow: Find the entry point of the temperature-density flow and perform control at the entry point to optimize the movement process of the density flow and increase its initial oxygen carrying capacity; Step 1.1: The unmanned boat is controlled by remote commands to sail from the downstream to the upstream of the lake and conduct underway observations; after sailing continuously for 2% of the total length of the lake, it pauses and measures the water depth at the pause point using a bottom-penetrating sonar (1). The multi-parameter water quality sensor (3) is driven by the first winch motor (2-1) to be lowered uniformly from the water surface to the bottom of the water at a speed not exceeding 0.25 m / s. During this period, water temperature data is collected at a frequency of not less than 1 Hz to obtain a vertical water temperature profile; Step 1.2: The vertical temperature gradient is derived from the vertical depth to identify the water temperature structure. Areas with a water temperature gradient of at least 2°C / m are designated as thermoclines. If only one thermocline is identified at a pause point during the underway observation, this indicates no temperature gradient intrusion, which is considered Stage I. If two thermoclines are identified at a pause point, with a vertical spacing of at least 2 m, this indicates the presence of temperature gradient intrusion, which is considered Stage II. If no thermocline is identified at a pause point, meaning the maximum vertical temperature gradient is less than 2°C / m, this indicates the unmanned vessel has reached the river channel of the lake or reservoir, which is considered Stage III. Step 1.3: Determine the entry point of the temperature-density current. The spatial critical point where stage III transitions to stage II is the entry point of the temperature-density current. To accurately locate the entry point through underway observation, the unmanned vessel should sail upstream of the lake in both states I and II, and downstream of the lake in state III. This binary method is then used to determine the location of the entry point of the temperature-density current. Step 1.4: Conduct temperature differential gravity flow entry point control; Step 1.5: Once the temperature-density current's movement characteristics are adjusted, its entry point and depth will also change accordingly. Repeat Steps 1.3-1.4 repeatedly to confirm that the temperature-density current's movement and oxygen-carrying characteristics are adjusted to a more ideal state. Step 2: Control the relay points of the temperature-difference gravity flow: The relay points are where the temperature-difference gravity flow is about to stop moving or the dissolved oxygen it carries is about to be exhausted. Find the relay points of the temperature-difference gravity flow and carry out control at the relay points to continue the movement of the temperature-difference gravity flow and replenish the dissolved oxygen it carries, so that it can continue to move and replenish the dissolved oxygen at the bottom of the lake.

2. The control method of the temperature-difference density flow control device for improving lake bottom hypoxia according to claim 1, characterized in that: The multi-parameter water quality sensor (3), the water outlet (5-1) and the water pumping port (5-2) are respectively connected to corresponding hoisting devices.

3. The control method of the temperature-difference density flow control device for improving lake bottom hypoxia according to claim 2, characterized in that: The multi-parameter water quality sensor (3) is connected to the first reel (4-1) via a rope, and the input end of the first reel (4-1) is connected to the output end of the first hoisting motor (2-1); the water outlet (5-1) is connected to the second reel (4-2) via a rope, and the input end of the second reel (4-2) is connected to the output end of the second hoisting motor (2-2); the water pumping port (5-2) is connected to the third reel (4-3) via a rope, and the input end of the third reel (4-3) is connected to the output end of the third hoisting motor (2-3).

4. The control method of the temperature-difference density flow control device for improving lake bottom hypoxia according to claim 2, characterized in that: The signal output ends of the bottom-penetrating sonar (1) and the multi-parameter water quality sensor (3) are both connected to the input end of the controller (11), and the output end of the controller (11) is respectively connected to the water pump (7), the aerator (8), the refrigerator (9), and the winch control end.

5. The control method of the temperature difference density flow control device for improving lake bottom hypoxia according to claim 1, characterized in that: A solar photovoltaic panel (10) is provided on the upper side of the unmanned boat, an output end of the solar photovoltaic panel (10) is connected to an input end of a battery, and a propeller propulsion device (12) is provided on the rear side of the unmanned boat.

6. The method for controlling a temperature-difference density flow control device for improving hypoxia at the bottom of a lake or reservoir according to claim 1, characterized in that: The specific process of carrying out the entry point control of the temperature-difference gravity flow in Step 1.4 is as follows: the unmanned boat is made to sail to the entry point of the temperature-difference gravity flow and pause, the bottom-penetrating sonar (1) measures the water depth of the entry point, and then the multi-parameter water quality sensor (3) is driven by the first winch motor (2-1) to move to a height of 1 m above the riverbed and hover, continuously monitoring the water temperature and dissolved oxygen concentration of the temperature-difference gravity flow; at the same time, the third winch motor (2-3) and the second winch motor (2-2) respectively control the water inlet (5-2) and the water outlet (5-1) to be lowered to a height of 1 m above the riverbed. m height and suspended to avoid the temperature-difference gravity flow control measures disturbing the sediment; then, the water is pumped by the water pump (7) to the aerator (8) for oxygenation treatment to adjust the oxygen carrying capacity of the temperature-difference gravity flow, and then to the refrigerator (9) for cooling treatment to adjust the movement capacity of the temperature-difference gravity flow; the real-time monitoring of the multi-parameter water quality sensor (3) reflects the temperature-difference gravity flow control effect. When the water temperature recorded by the multi-parameter water quality sensor (3) is consistent with the bottom water temperature of stage I, the movement characteristic control of the entry point of the temperature-difference gravity flow is completed; when the dissolved oxygen concentration recorded by the water quality sensor is consistent with the saturated dissolved oxygen concentration corresponding to the water flow temperature, the oxygen carrying characteristic control of the entry point of the temperature-difference gravity flow is completed; Step 1.5: Once the temperature-density current's movement characteristics are adjusted, its entry point and depth will also change accordingly. Repeat Steps 1.3-1.4 repeatedly to confirm that the temperature-density current's entry movement and oxygen-carrying characteristics are adjusted to a more ideal state.

7. The method for controlling a temperature-difference density flow control device for improving hypoxia at the bottom of a lake or reservoir according to claim 1, characterized in that: The Step 2 is specifically as follows: Step 2.1: Determine the relay point of the temperature-gravity current. The water temperature relay point and dissolved oxygen relay point of the temperature-gravity current may not coincide and need to be explored separately. The water temperature relay point is the spatial critical point where stage II transitions to stage I as described in Step 1.

2. To determine the water temperature relay point through underway observation, the unmanned vessel is instructed to sail upstream of the lake in state I and downstream of the lake in state II. The water temperature relay point of the temperature-gravity current is finally determined through a binary method. When the unmanned vessel conducts aerial surveys between the entry point of the temperature-gravity current and the movement relay point, if the measured dissolved oxygen concentration at the bottom of the lake is less than 2 mg / L, it indicates that the dissolved oxygen carried by the temperature-gravity current has almost been replenished to the bottom water body, and therefore the area is marked as the dissolved oxygen relay point of the temperature-gravity current. Step 2.2: Carry out water temperature relay regulation of temperature-difference gravity flow; make the unmanned boat sail to the water temperature relay point of temperature-difference gravity flow and pause, and use the bottom-penetrating sonar (1) to measure the water depth of the diving point; then use the first winch motor (2-1) to drive the multi-parameter water quality sensor (3) to move continuously in the vertical direction, and analyze the vertical water temperature structure changes in the area according to Step 1.2; at the same time, the third winch motor (2-3) and the second winch motor (2-2) respectively control the water inlet (5-2) and the outlet (5-1) to be lowered to a height of 1 m from the riverbed and suspended, and then use the water pump (7) to pump the bottom water into the refrigerator (9) for cooling and then transport it back to the bottom of the lake reservoir, thereby continuing the movement process of temperature-difference gravity flow; when the real-time monitoring results of the multi-parameter water quality sensor (3) show that the above-mentioned regulation has caused the area to change from stage I to stage II, the water temperature relay regulation of temperature-difference gravity flow is completed; Step 2.3: Carry out dissolved oxygen relay regulation of temperature-difference gravity flow; make the unmanned boat sail to the dissolved oxygen relay point of temperature-difference gravity flow and pause, and use the bottom-penetrating sonar (1) to measure the water depth of the diving point; then use the first winch motor (2-1) to drive the multi-parameter water quality sensor (3) to move to a height of 1 m above the riverbed and hover, and continuously monitor the dissolved oxygen concentration of the bottom water; at the same time, the third winch motor (2-3) and the second winch motor (2-2) respectively control the water inlet (5-2) and the outlet (5-1) to be lowered to a height of 1 m above the riverbed and suspended, and then use the water pump (7) to pump the bottom water to the aerator (8) for oxygenation and then transport it back to the bottom of the lake, so that the temperature-difference gravity flow can carry more dissolved oxygen to alleviate the hypoxia phenomenon at the bottom of the lake; when the real-time monitoring results of the multi-parameter water quality sensor (3) show that the above-mentioned regulation has made the dissolved oxygen concentration of the temperature-difference gravity flow close to saturation, the dissolved oxygen relay regulation of the temperature-difference gravity flow is completed.

Images