A method for delaying boundary layer transition control

Abstract

This invention relates to a method for delaying boundary layer transition control, comprising: a first temperature-controlled pipeline installed at the bow of a rotating body for cooling / heating the bow to delay boundary layer transition; and a second temperature-controlled pipeline installed midships of the rotating body, the second temperature-controlled pipeline having a negative temperature correlation with the first temperature-controlled pipeline, for heating / cooling the midships to reduce their operating resistance. This invention features a compact and reasonable structure, is easy to operate, and through a simple structural combination, achieves the effect of delaying boundary layer transition in liquids and air, as well as reducing resistance, by installing temperature-controlled pipelines with a negative temperature correlation at the bow and midships. Furthermore, by adjusting the installation structure of the two temperature-controlled pipelines and their correlation, better temperature control is achieved, making it highly practical.

Description

Technical Field

[0001] This invention relates to the field of shipbuilding technology, and in particular to a method for delaying boundary layer transition control. Background Technology

[0002] For objects moving in water, a thin boundary layer forms on the object's surface along the flow direction; this is called boundary layer flow. Figure 1 Boundary layer flow is generally divided into laminar flow region, transition region, and fully developed turbulent flow region. The transition region is the area where laminar flow transitions to turbulent flow, and the process of this transition is called fluid transition. We know that in turbulent flow, fluid motion is disordered, with large velocity and pressure fluctuations in all directions, resulting in greater excitation of the structure; while in laminar flow, fluid flow is stable, with smaller velocity and pressure fluctuations, resulting in less excitation of the structure. If the boundary layer transition can be delayed and the laminar flow length extended, the fluid-induced vibrations on the structure can be reduced, and further, adverse effects such as noise can be reduced.

[0003] Fluid transition is primarily influenced by the critical Reynolds number. cr =Ux tr / γ, Generally speaking, given a constant fluid characteristic such as the incoming flow velocity U, the critical Reynolds number is already determined, i.e., the transition position x. tr It has been largely determined that the transition region changes relatively little with other factors, but in reality, if the fluid viscosity coefficient γ can be adjusted to increase, the critical Reynolds number Re... cr If U remains unchanged, then the transition position x can be extended. tr .

[0004] Therefore, this patent proposes a method for delaying boundary layer transition control, thereby delaying the transition position and extending the laminar flow region. Summary of the Invention

[0005] To address the shortcomings of existing production technologies, the applicant provides a method for delaying boundary layer transition control. This patent improves the kinematic viscosity coefficient through temperature control. This method is easy to implement, does not require the injection of additional substances into the fluid or damage to the outer shell of the object, and has good application prospects.

[0006] The technical solution adopted in this invention is as follows:

[0007] A method for delaying boundary layer transition control, applied to a rotating body, includes:

[0008] A temperature control pipeline is provided at the bow of the rotating body for cooling / heating the bow to delay boundary layer transition;

[0009] A second temperature control pipeline is provided in the midship section of the rotating body. The temperature of the second temperature control pipeline is negatively correlated with that of the first temperature control pipeline. It is used to heat / cool the midship section to reduce its operating resistance.

[0010] Optionally, when the medium is liquid, temperature control line one cools the bow section, while temperature control line two heats the midship section.

[0011] Optionally, when the medium is air, one pair of temperature control lines heats the bow section, while the other pair of temperature control lines cools the midship section.

[0012] Optionally, it also includes a control component, which is connected to both temperature control line one and temperature control line two, and the temperature control methods for temperature control line one and temperature control line two include separate control and coordinated control.

[0013] Optionally, in the coordinated control method, the control components include a compressor, a throttle valve, a drive pump, and an auxiliary piping system, and the aforementioned components are respectively connected to temperature control piping one and temperature control piping two to achieve opposite temperature control.

[0014] Optionally, both the first and second temperature control pipes are coiled to increase the contact area.

[0015] Optionally, the temperature control pipeline is connected to the inner wall of the bow section, coupled to the bow shell, and fitted together.

[0016] Optionally, the second temperature control pipeline is sleeved on the outer wall of the midship, and the midship is also provided with a streamlined cover that covers the second temperature control pipeline to reduce resistance.

[0017] Optionally, the bow of the rotating body is streamlined, and the midships of the rotating body is cylindrical.

[0018] The beneficial effects of this invention are as follows:

[0019] This invention features a compact and reasonable structure, and is easy to operate. Through a simple structural combination, it achieves the effect of delaying boundary layer transition in liquids and air, as well as reducing resistance, by setting temperature-negative temperature control pipelines in the bow and midship sections. At the same time, by adjusting the installation structure of the two temperature control pipelines and the relationship between them, better temperature control can be achieved, making it highly practical.

[0020] In addition, the present invention also has the following advantages:

[0021] (1). Temperature control pipeline 1 is installed inside the bow and is used to cool / heat the bow to delay the boundary layer transition. Temperature control pipeline 1 is arranged below the shell to reduce the surface temperature of the object. Through heat conduction, the temperature of the fluid flowing through the surface of the object is reduced, thereby increasing the viscosity of the water and delaying the transition of the fluid.

[0022] (2) The heat absorbed by the temperature control pipeline is dissipated on the surface of the midship through the compressor and pipeline system and the heat dissipation system. Since the downstream boundary layer of the object is a fully developed turbulent flow, heat dissipation in the fully developed turbulent flow does not affect the fluid flow state, and at the same time, it heats the downstream water. As the viscosity of the water decreases, it can also reduce the frictional resistance of the object to a certain extent.

[0023] (3). This invention can be used in both water and air to delay boundary layer transition, thus improving its applicability. When the medium is liquid, temperature control pipeline one cools the bow section while temperature control pipeline two heats the midsection. When the medium is air, temperature control pipeline one heats the bow section while temperature control pipeline two cools the midsection. When applied to air, since the viscosity of the gas changes with temperature in the opposite way to that of water, it is necessary to increase the viscosity of the gas by heating. This control method is also applicable, only the process is reversed.

[0024] (4). In the coordinated control mode, the control components include a compressor, a throttle valve, a drive pump and an auxiliary pipeline system, and the aforementioned components are respectively connected to temperature control pipeline one and temperature control pipeline two to achieve opposite temperature control. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the hybrid boundary layer of the present invention.

[0026] Figure 2 This is a three-dimensional structural schematic diagram of the present invention.

[0027] Figure 3 This is a cross-sectional view of the present invention.

[0028] Figure 4 This is a schematic diagram of the connection structure of temperature control pipeline one, temperature control pipeline two, and control component in this invention.

[0029] Figure 5 For the present invention Figure 3 A schematic diagram of the partial connection structure between the mid-bow section and the temperature control pipeline.

[0030] Figure 6 This is a temperature-viscosity coefficient curve of the bow section in this invention.

[0031] Among them: 100, rotating body; 200, temperature control pipeline one; 300, temperature control pipeline two; 400, compressor; 500, throttle valve; 600, drive pump; 700, auxiliary pipeline system;

[0032] 101. Bow; 102. Midships.

[0033] Rotating body 100; Temperature control pipeline one 200; Temperature control pipeline two 300; Compressor 400; Throttling valve 500; Drive pump 600; Auxiliary piping system 700; Bow section 101 Detailed Implementation

[0034] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0035] like Figures 1-6 As shown, this embodiment discloses a method for delaying boundary layer transition control, including: a rotating body 100, a temperature control pipeline 200 and a temperature control pipeline 300. By controlling the negative correlation between the temperature control pipeline 200 and the temperature control pipeline 300, the method achieves the effect of delaying boundary layer transition between different media and reducing the operating resistance of the midship 102.

[0036] The rotating body 100 includes a streamlined bow 101 and a cylindrical midship section 102.

[0037] Temperature control pipe 200 is installed inside the bow 101 and is used to cool / heat the bow 101 to delay boundary layer transition. Temperature control pipe 200 is arranged below the shell to reduce the surface temperature of the object. By means of heat conduction, the temperature of the fluid flowing through the surface of the object is reduced, thereby increasing the viscosity of the water and delaying the transition of the fluid.

[0038] Temperature control pipe 2 300 is installed in midship section 102, and the temperature of temperature control pipe 2 300 is negatively correlated with that of temperature control pipe 1 200. It is used to heat / cool midship section 102 to reduce the operating resistance of midship section 102.

[0039] Furthermore, the heat absorbed by the temperature control pipe 200 is dissipated on the surface of the midship section 102 through the compressor 400 and the piping system via the heat dissipation system. Since the downstream boundary layer of the object is fully developed turbulence, heat dissipation in fully developed turbulence does not affect the fluid flow state, and at the same time, it heats the downstream water. As the viscosity of the water decreases, it can also reduce the frictional resistance of the object to a certain extent.

[0040] It also includes a control component, which is connected to both temperature control line 200 and temperature control line 300. The temperature control methods for temperature control line 200 and temperature control line 300 include separate control and coordinated control.

[0041] In the coordinated control mode, the control components include a compressor 400, a throttle valve 500, a drive pump 600, and an auxiliary piping system 700. The aforementioned components are respectively connected to temperature control piping 200 and temperature control piping 300 to achieve opposite temperature control.

[0042] Specifically, the cooling device in this patent operates on the following principle: a low-temperature, low-pressure gas-liquid mixture passes through a temperature-controlled pipeline 200, absorbs heat from the fluid in the transition zone, and becomes a low-temperature, low-pressure gas. After being compressed by a compressor 400, the low-temperature, low-pressure gas becomes a high-temperature, high-pressure gas. This high-temperature, high-pressure gas then passes through a temperature-controlled pipeline 300, exchanges heat with the external fluid, and condenses into a high-temperature, high-pressure liquid after its temperature decreases. Driven by a pump 600, the liquid flows through a throttling valve 500, which reduces the pressure of the high-temperature, high-pressure liquid. The high-temperature, high-pressure liquid expands and outputs the low-temperature, low-pressure gas-liquid mixture, which then proceeds to the next cycle. This cooling device operates on a relatively mature principle and is one example of the implementation scheme in this patent. The purpose of the cooling device is to provide a cooling source in the boundary layer transition control method. Other methods, such as phase change sublimation, can also be used to obtain a cooling source, with the heating principle being the opposite.

[0043] In this embodiment, the medium is liquid. Temperature control pipeline 200 cools the bow section 101, while temperature control pipeline 300 heats the midship section 102.

[0044] In another implementation, when the medium is air, temperature control line 200 heats the bow section 101, while temperature control line 300 cools the midship section 102. When applied to air, since the viscosity of gas changes with temperature in the opposite way to that of water, it is necessary to increase the viscosity of the gas by heating. This control method is also applicable, only the process is reversed.

[0045] Both temperature control pipe 1 (200) and temperature control pipe 2 (300) are coiled to increase the contact area, but in practice, a sleeve structure can also be used.

[0046] The temperature control line 200 is coupled to the shell of the bow section 101, which can increase the contact area between the temperature control line 200 and the fluid, thereby improving the temperature control effect and delaying the boundary layer transition.

[0047] In another embodiment, the temperature control line 200 is connected to the inner wall of the bow section 101.

[0048] In another embodiment, the midship section 102 is also provided with a streamlined cover that covers the second temperature control pipe 300 to reduce resistance. The front and rear ends of the cover are streamlined and the middle is hollowed out, which can ensure the heat dissipation effect of the second temperature control pipe 300 while reducing resistance.

[0049] In actual operation:

[0050] First, the flow direction in the transition region is determined by the critical Reynolds number. Based on empirical formulas, a critical Reynolds number of 5 × 10⁻⁶ can be selected. 5 Calculate the transition initiation position and transition range based on the critical Reynolds number: x tr =Re crγ / U,

[0051] Taking water as an example, when the temperature is 20°C, temperature control pipes 200 and 300 are used to conduct heat. Their form is not limited to pipes; they can be any type of cooling and heat dissipation system. The purpose is to change the temperature of the fluid in the boundary layer of an object's surface through heat conduction.

[0052] like Figure 6 The table below shows the temperature and viscosity coefficient curves. From the graph, it can be seen that for every 10°C decrease in the bow temperature, the viscosity coefficient increases by approximately 30%. Assuming the water density remains constant (in reality, the water density decreases as the bow 101 increases, but the overall effect is not significant), and keeping the incoming water velocity U and critical Reynolds number Re constant... cr If so, the starting position of the transition will be delayed by approximately 30%.

[0053] f(t) = -0.00006x 3 +0.0089x 2 -0.5464x + 17.868, 0 <x<60

[0054] 0 999.9 17.92 10 999.7 13.1 20 998.2 10.09 30 995.7 8 40 992.2 6.54 50 988.1 5.49 60 983.2 4.69

[0055] The specific implementation method is as follows:

[0056] First, the approximate transition position of the underwater object under incoming flow conditions is obtained using empirical fluid dynamics formulas. Then, the critical Reynolds number for boundary layer transition, Re, is defined. cr =Ux tr / γ, the critical Reynolds number can be taken as 5 × 10⁻⁶. 5 Then calculate the starting position x of the transition. tr At this time, x tr This is an estimated value. Fluid transition is not a transient process, but a gradual transition within a certain range. The range of this transition zone can be obtained based on empirical values, such as... Figure 1 The estimated transition range is x. tr ±l, where l is the characteristic width of the object, such as radius (0.5D), etc. (L represents the length of the object, D is the diameter of the rotating body 100, and 0.5D represents the laying width of the temperature control pipe 200. The temperature control pipe 200 is laid within a width of 0.5D upstream and downstream of the transition position.)

[0057] Taking the rotating body 100 as an example, the surface boundary layer delayed transition control system includes a temperature control pipeline 200, a temperature control pipeline 300, a compressor 400, a throttle valve 500, a drive pump 600, and an auxiliary pipeline system 700. The temperature control pipeline 200 is located in the transition region at the bow of the rotating body 100, and delays the transition by reducing the temperature of the fluid in the boundary layer at the bow. The heat absorbed by the temperature control pipeline 200 is transferred to the temperature control pipeline 300 through the loop system, and then transferred to the fluid in the middle and rear section of the rotating body 100 through heat exchange. The fluid medium's kinematic viscosity decreases, and the fluid medium's viscous resistance will inevitably decrease, thereby improving the operating effect of the rotating body 100.

[0058] The temperature control piping system 200 is located beneath the outer casing. Through a specific manufacturing process, the temperature control piping system 200 is embedded into the housing of the rotating body 100, such as... Figure 5 As shown, it can also be coupled to the outer shell of the rotating body 100 in other ways. The temperature control pipe 200 conducts heat through the shell of the rotating body 100 and absorbs heat from the fluid boundary layer. This pipe is buried under the shell and does not damage the outer surface shape of the shell. In the transition region, the outer shell of the rotating body 100 can also be made of metal or other materials with high thermal conductivity, which can improve the cooling effect.

[0059] Temperature control pipe 2 300 is arranged outside the rear half of the shell of rotating body 100, directly exchanging heat with the incoming flow. Since the flow state in the boundary layer of the rear half of the shell of rotating body 100 is already fully developed turbulence, arranging temperature control pipe 2 300 here will not disrupt the flow state, thus minimizing overall flow disturbance to rotating body 100. Furthermore, as the water temperature rises, the water viscosity decreases, which can also reduce frictional resistance to some extent. Temperature control pipe 2 300 can be flexibly modified according to the application of this patent; its main purpose is to release the fluid heat absorbed by temperature control pipe 1 200 in the transition region to other areas of the fluid.

[0060] This invention features a compact and rational structure, and is easy to operate. Its main principle is to increase the viscosity of the local fluid by reducing the fluid temperature in the boundary layer transition region, thereby delaying the transition point and increasing the laminar flow region. Simultaneously, through a simple structural combination, temperature-controlled pipelines with negative temperature correlation are provided in the bow section 101 and midship section 102, achieving the effect of delaying boundary layer transition in liquids and air, as well as reducing resistance. Furthermore, by adjusting the installation structure of the two temperature-controlled pipelines and the correlation between them, better temperature control is achieved, making it highly practical.

[0061] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A method for delaying boundary layer transition control applied on a body of revolution (100), characterized in that, include: A temperature control pipeline (200) is provided on the inner wall of the bow (101) of the rotating body (100). The temperature control pipeline (200) does not damage the outer surface of the rotating body (100). The temperature control pipeline (200) is used to cool / heat the bow (101) to delay the boundary layer transition. A second temperature control pipeline (300) is provided in the midship section (102) of the rotating body (100). The temperature control pipeline (300) is negatively correlated with the temperature control pipeline (200) and is used to heat / cool the midship section (102) to reduce the running resistance of the midship section (102). When the medium is liquid, temperature control line one (200) cools the bow (101), while temperature control line two (300) heats the midship (102); When the medium is air, temperature control line one (200) heats the bow (101), while temperature control line two (300) cools the midship (102).

2. The method for delaying boundary layer transition control as described in claim 1, characterized in that: It also includes a control component, which is connected to both temperature control line one (200) and temperature control line two (300). The temperature control methods for temperature control line one (200) and temperature control line two (300) include separate control and coordinated control.

3. The method for delaying boundary layer transition control as described in claim 2, characterized in that: In the coordinated control mode, the control components include a compressor (400), a throttle valve (500), a drive pump (600), and an auxiliary pipeline system (700), and the control components are respectively connected to temperature control pipeline one (200) and temperature control pipeline two (300) to achieve opposite temperature control.

4. The method for delaying boundary layer transition control as described in claim 1, characterized in that: Both temperature control pipe one (200) and temperature control pipe two (300) are coiled to increase the contact area.

5. The method for delaying boundary layer transition control as described in claim 1, characterized in that: The temperature control pipeline (200) is coupled to and fitted into the bow (101) housing.

6. The method for delaying boundary layer transition control as described in claim 1, characterized in that: The second temperature control pipe (300) is sleeved on the outer wall of the midship (102), and the midship (102) is also provided with a streamlined cover that covers the second temperature control pipe (300) to reduce resistance.

7. The method for delaying boundary layer transition control as described in claim 1, characterized in that: The bow (101) of the rotating body (100) is streamlined, and the midship (102) of the rotating body (100) is cylindrical.

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