A design method for safe water rescue training structure

Abstract

The present invention relates to a design method for a safe water rescue training structure, and a mathematical model of a water rescue training structure is established, wherein the water rescue training structure includes an inlet pool, a waterway and an outlet stilling pool; grid division and boundary condition processing; the waterway includes an intense flow channel and a gentle flow channel that are alternately connected in sequence, and the intense flow channel and / or the gentle flow channel are equipped with obstacles; the RNG k‑ε model is used to simulate the turbulent flow starting from the inlet pool, passing through the waterway and finally flowing to the outlet stilling pool; the compressible gas-water two-phase transient flow is described by the VOF model; the water flow pattern, water level and flow velocity of each intense flow channel and the gentle flow channel under each design flow rate of the waterway are calculated to see whether they meet the design requirements; the intense flow channel and the gentle flow channel are alternately arranged, so that the trainees retain a certain amount of physical strength to prevent danger. The RNG k‑ε model and the VOF model can be used to calculate whether the water flow pattern, water level and flow velocity of each intense flow channel and the gentle flow channel under each design flow rate of the waterway meet the design requirements.

Description

Technical Field

[0001] The invention relates to the technical field of hydraulic numerical simulation, and in particular to a design method for a safe water rescue training structure. Background Art

[0002] Affected by extreme weather, the number of people trapped due to floods has increased significantly, water rescue tasks have become increasingly arduous, and the rescue situation has become increasingly severe. For rescuers, not only do they need special equipment for rapids rescue, but more importantly, they need to have intensive training and practice experience in rapids. However, if they train in natural rivers, they will not only be affected by seasonality, but also have uncontrollable risks. Therefore, water rescue simulation facilities have emerged;

[0003] For example, the Chinese invention patent with the patent publication number CN115909837A discloses a hydraulic design method for rapids waterways and a comprehensive training base for water rescue, and proposes a calculation method for hydraulic parameters of different flow patterns in rapids waterways, so that a variety of rapids flow patterns in natural rivers can be accurately simulated in the waterway; it provides technical requirements and design standards for reference for training areas with different flow patterns in rapids waterways to ensure the personal safety of trainees and training effects;

[0004] Rescuers will expend a lot of physical energy when training in intense flow channels. In actual use, it is found that they are physically exhausted due to continuously passing through multiple intense flow channels, and are in danger of being in intense flow channels. At the same time, when designing water rescue structures, they cannot understand their structural effects in a timely manner, and are unclear whether the characteristics of the designed water rescue structures meet the needs. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a method for designing a safe water rescue training structure to solve the above problems.

[0006] The present invention provides the following technical solutions:

[0007] A method for designing a safe water rescue training structure, comprising:

[0008] Establish a mathematical model of the water rescue training structure, which includes the water inlet pool, waterway and outlet stilling pool;

[0009] The water channel includes a violent flow channel and a gentle flow channel which are connected alternately in sequence, and obstacles are arranged in the violent flow channel and / or the gentle flow channel; the violent flow channel and the gentle flow channel are essentially rapid flow and slow flow;

[0010] Meshing and boundary condition processing;

[0011] The RNG k-ε model is used to simulate the turbulent flow starting from the inlet pool, passing through the waterway and finally flowing to the outlet stilling basin; the RNGK-ε model is classified based on turbulence calculation and is suitable for turbulent flow with strong vortices.

[0012] The VOF model is used to describe the transient flow of compressible gas-water two-phase. The VOF model is classified from the simulation of the water-gas interface and is suitable for models with obvious water-gas interfaces.

[0013] The combined use of the RNG k-ε model and the VOF model can better simulate the flow of two substances, air and water, with a clear interface between the two.

[0014] Calculate the flow pattern, water level and flow velocity of each intense flow channel and gentle flow channel at each design flow rate of the waterway to see whether they meet the design requirements;

[0015] If the design requirements are not met, at least one of the obstacle size, obstacle combination or waterway bottom slope shall be adjusted until the design requirements are met.

[0016] Preferably, the violent flow channel is a boiling flow, a frowning flow, a V-shaped flow, a tumbling flow or a white water area. The violent flow channel often has a high flow velocity and is relatively dangerous; the gentle flow channel is a frowning flow, a covering flow, a smiling flow, a transition zone and a vortex flow. The inside of the frowning flow obstacle is a rest area and a safe area, and the outside is a contraction section with a high flow velocity and is dangerous.

[0017] Preferably, the design method of the boiling flow is as follows:

[0018] Calculate boiling flow rate per width q 沸腾 :

[0019]

[0020] Where Q is the water supply capacity of the waterway pump or the maximum flow rate upstream, m 3 / s; B 沸腾 is the width of the boiling water channel, m; q 沸腾 is the boiling flow rate per width, m 3 / (s·m);

[0021] In hydraulics, the flow calculation formula for weir flow is:

[0022]

[0023] in is the lateral contraction coefficient, , is the flooding coefficient, .

[0024] Where m is the flow coefficient and has no unit;

[0025] b is the water width of the weir crest, m;

[0026] g is the acceleration due to gravity, g=9.81m / s 2 .

[0027] H is the water head on the boiling flow weir, m;

[0028] There is no shrinkage at the weir top, and the downstream water level is lower than the weir top, so there is no flooding effect. , ;

[0029] The formula becomes:

[0030]

[0031] Divide both sides by b, and the flow Q on the left becomes the single-width flow q, and the unit of single-width flow q is m 3 / (s·m) or m 2 / s;

[0032]

[0033] When designing a waterway, a broken line weir is often used for ease of construction. The flow coefficient m of the broken line weir ranges from 0.33 to 0.42, with most of the flow coefficients concentrated at 0.38. Substitute m=0.38 and g=9.81m / s 2 ,available:

[0034]

[0035]

[0036]

[0037] According to the boiling flow single width flow q 沸腾 Preliminary assessment of water head over boiling flow weir :

[0038]

[0039] calculate Size, select the quick calculation formula of water head H according to the corresponding range:

[0040]

[0041] Where δ is the thickness of the top of the water head on the boiling flow weir, m;

[0042] Boiling flow length L 沸 , can be calculated based on the number of training boats:

[0043] L 沸 =10+N L艇 ;

[0044] Among them, 10 is the unit of length, m; L 艇 is the length of the training boat, m; N is the number of training boats.

[0045] Preferably, in hydraulics, the water flow height of a bend can be calculated according to the following formula:

[0046] H 弯道处外侧沟高 =H 均 +0.5h 内外侧水位差 + (0.3~0.5)

[0047]

[0048]

[0049] The above height is in meters. The original formula safety super height (0.3m~0.5m) is slightly reduced to 0.15m according to the on-site water discharge effect and operation requirements;

[0050] Therefore, the waterway has at least one bend. When the frown flow is arranged at the bend, the obstacle is arranged outside the bend and the obstacle arrangement direction is perpendicular to the water flow or points to the center of the bend. The calculation method of the obstacle height therein is as follows:

[0051] When the frown flow is arranged in a curve section, the height of the obstacle outside the curve can be estimated according to the following formula:

[0052]

[0053] H 外 Design height of the outer obstacle of the frown flow curve section, m;

[0054] H 皱均 is the average water depth of the Frown Flow Bend, m;

[0055] V 皱 is the flow velocity of the frown flow bend, m / s;

[0056] B 皱 is the width of the frown flow bend, m;

[0057] R 皱 is the bend radius of the outer edge of the frown flow bend, m;

[0058] g is the acceleration due to gravity, m / s 2 .

[0059] Preferably, the method for calculating the V-shaped flow water surface height and the V-shaped flow obstacle height is as follows:

[0060] When the V-shaped flow obstacle is arranged perpendicular to the water flow direction, Figure 2 Analysis shows that the turning radius R is v , the water surface height △H is calculated according to the following formula (g=9.81m / s 2 ):

[0061]

[0062] The original formula safety super height (0.3m~0.5m) was slightly reduced to 0.15m according to the on-site water discharge effect and operation requirements. The height calculation formula is:

[0063]

[0064] Among them, H V均 is the average water depth of the V-shaped flow section, m; V is the flow velocity of water in the V-shaped flow section, m / s.

[0065] Preferably, the tumbling flow increases the flow velocity by using a steep slope or by reducing the cross-sectional width, the flow velocity is greater than 4 m / s, and the contraction width is less than 1 / 2B 翻 , where B 翻 is the width of the tumbling waterway, and the steep slope ratio is 1:5~1:10;

[0066] The tumbling flow slope bottom is connected to the flat bottom, and the downstream tumbling flow is deep Calculated according to the conjugate water depth formula:

[0067]

[0068] Fr 1 is the Froude number of the tumble flow contraction section, Fr 1 Greater than 2.5;

[0069] h 1 is the water depth of the contraction section of the tumbling flow, h 1 Greater than 0.2m;

[0070] Tumble flow length calculation formula:

[0071]

[0072] When L 翻 <10, take L 翻 =10m.

[0073] Preferably, the smiling flow obstacle forms backflow on the water-facing surface and forms vortex backflow on the water-receiving surface, and the size parameters of the smiling flow obstacle are controlled according to the following formula:

[0074]

[0075] The water flow of slow flow Karman vortex is extremely slow, and for waterways, low Reynolds number flow is very rare. It is difficult to achieve Karman vortex in the slow flow state of similar engineering smiling flow. Therefore, this formula is applicable to most turbulent Karman vortex calculations. That is, the Reynolds number needs to be greater than 3 10 6 The Reynolds number formula is:

[0076]

[0077] Where V is the water flow velocity in m / s. is the kinematic viscosity of water, which is 1.003 at 20° water temperature 10 -6 , to simplify the calculation, take 1.0 10 -6 .

[0078] d is the characteristic length of the flow, d is the ratio of the water flow area A to the wetted perimeter χ, in meters, and the wetted perimeter χ is the perimeter of the water flow section, such as Figure 4 As shown, for the smile flow:

[0079] χ = B 微 -L 微 +4h 微

[0080] Therefore, generating a smiling flow vortex requires:

[0081]

[0082] The water flow area A = (B 微 -L 微 )h 微 , wet week ;

[0083]

[0084] Among them, V 微 L is the flow velocity of the upstream water flow in the smiling flow, m / s; 微 L is the length of the smiling flow obstacle perpendicular to the water flow direction, m; 微 Value 1 / 3B 微 ~1 / 2B 微 , B 微 is the width of the smiling waterway, m; the formula is applicable to water temperatures of 10℃~20℃; h 微 is the water depth of the smiling flow section, m.

[0085] Preferably, the vortex flow is adjusted according to the training intensity, the width of the vortex flow area is greater than 8m, the vortex flow effect is affected by the running flow rate, the vortex flow velocity is high, and the water flow is in a torrent state. At this time, the minimum single-width flow rate q of the upstream waterway of the vortex area can be calculated according to the following formula:

[0086]

[0087] When the vortex water depth is h 漩 When the minimum value is 0.6m, q 漩 =1.455m³ / (s·m);

[0088] The vortex flow rate is:

[0089]

[0090] Q 漩 The traffic volume for single-person training should not exceed 1.455B. 漩 If the training water depth increases, Q can be adjusted according to the above formula 旋 size;

[0091] Among them, Q 漩 is the flow rate of the vortex flow section, m 3 / s; B 漩 is the width of the vortex flow channel, m; h 漩 is the water depth of the eddy flow section, m;

[0092] When Fr < 1, the water flow is slow;

[0093] When Fr = 1, the water flow is critical flow;

[0094] When Fr>1, the water flow is a torrent, and the upstream end of the vortex flow is in a torrent state, which is characterized by the Froude number Fr>1;

[0095] For an open channel, the flow rate Q can be calculated based on the flow velocity V and the cross-sectional area A.

[0096]

[0097] Single width flow:

[0098]

[0099]

[0100] Substitute into the Fr calculation formula

[0101]

[0102]

[0103] g is the acceleration due to gravity, g=9.81m / s 2 Substituting into the above formula:

[0104]

[0105] When the depth of the vortex flow is h 漩 =0.6m, q 漩 >1.455m³ / (s·m).

[0106] Preferably, the water channel has at least one bend, and when the vortex flow is arranged at the bend, the internal obstacle is arranged inside the bend, and the upstream of the vortex flow at the bend is connected to a violent flow channel with the flow velocity concentrated in the middle; or

[0107] When the vortex flow is arranged at the straight position, a recessed area is arranged on one side of the straight, and an obstacle is arranged in the middle of the other side opposite to the straight.

[0108] Preferably, the transition zone is arranged between each flow state, and the minimum length L of the transition zone is 渡 It can be calculated based on the maximum upstream flow velocity:

[0109]

[0110] Among them, V max is the maximum flow velocity upstream of the transition zone, m / s; 3 is the time unit, seconds; when L 渡 When the calculated value is less than 10m, L 渡 = 10m. Based on the on-site real-life experience, it takes about 3 seconds to react from the sudden fall to judging the situation and taking action. The maximum flow velocity V max Multiply it by 3 seconds to get the safe length.

[0111] Preferably, the water level drop of the waterway is 6-7m, and the average slope is 3-6%; or

[0112] The water level of the waterway has a drop of 6.5m and an average slope of 3.48%; or

[0113] The water level drop of the waterway is 6.4m and the average slope is 5.37%.

[0114] Preferably, 3-12m 3 / s flow of water.

[0115] Preferably, the divided grids include structured grids and unstructured grids, the straight sections, water inlet pools and outlet stilling pools of the waterway adopt structured grids, and the guide wall edges and obstacles of the waterway adopt unstructured grids.

[0116] The present invention has the following beneficial technical effects:

[0117] The intense flow channel and the gentle flow channel are set alternately, so that the trainees can enter the gentle flow channel after passing through an intense flow channel area, and can perform small-amplitude movement training in the gentle flow channel to restore some physical strength, so that the trainees can retain a certain amount of physical strength to prevent danger. When conducting boat training in the flow channel, the transition area can ensure that the boat has enough adjustment space to maintain balance for rescue.

[0118] The RNG k-ε model is used to simulate the turbulence of the designed water rescue structure, and the VOF model is used to track and simulate the compressible gas-water two-phase transient flow, so as to calculate whether the flow pattern, water level and flow velocity of each intense flow channel and gentle flow channel under each design flow rate of the waterway meet the design requirements.

[0119] When designing the flow pattern combination, the upstream and downstream boundary conditions will change. Through the summarized calculation formula, the adjustment direction of obstacles in the waterway can be quickly determined, and the size parameters can be adjusted using the calculation results of the formula. BRIEF DESCRIPTION OF THE DRAWINGS

[0120] Figure 1 This is a schematic diagram of the multifunctional water rescue structure of the present invention;

[0121] Figure 2 Schematic diagram of the arrangement of the V-shaped flow obstacle perpendicular to the water flow direction of the present invention;

[0122] Figure 3 Schematic diagram of the relationship between the formation of Karman vortex and Reynolds number of the present invention;

[0123] Figure 4 It is a schematic diagram of the perimeter of the smiling water flow cross section of the present invention;

[0124] Figure 5 It is a schematic diagram of the frown flow arrangement at a bend of the present invention;

[0125] Figure 6 It is a schematic diagram of the vortex flow of the present invention when it is arranged in a curved section;

[0126] Figure 7 It is a schematic diagram of the vortex flow of the present invention when it is arranged in a straight line segment.

[0127] 1. Inlet pool; 2. Waterway; 3. Exit stilling pool; 21. Boiling flow; 22. V-shaped flow; 23. Frowning flow and covering flow; 24. Vortex flow; 25. Frowning flow; 26. Covering flow; 27. Smiling flow; 28. White water area. DETAILED DESCRIPTION

[0128] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0129] Example:

[0130] like Figure 1 As shown, two waterways 2 are designed between the water inlet pool 1 and the outlet stilling pool 3, and the water of the outlet stilling pool 3 is transported to the water inlet pool 1 through a circulation pump to achieve circulation.

[0131] like Figure 1 As shown, the water channel 2 on the left includes a boiling flow 21, a V-shaped flow 22, a frowning flow and a covering flow 23, a vortex flow 24 (rotating counterclockwise), a frowning flow 25, a vortex flow 24 (rotating clockwise), a vortex flow 24 (rotating counterclockwise), a V-shaped flow 22, a covering flow 26, a V-shaped flow 22 and a white water area 28 connected in sequence;

[0132] like Figure 1 As shown, the water channel 2 on the right includes a boiling flow 21, a frowning flow 25, a vortex flow 24 (rotating counterclockwise), a frowning flow 25, a smiling flow 27 and a V-shaped flow 22 connected in sequence, and the end can be a covering flow or a tumbling flow according to the water level flow;

[0133] The violent flow channel is a boiling flow 21, a frowning flow 25, a V-shaped flow 22, a tumbling flow or a white water area 28; the gentle flow channel is a covering flow 26, a smiling flow 27, a transition zone or a vortex flow 24; at most three violent flow channels can be connected at the same time.

[0134] When the rapid flow changes to the slow flow, a flow pattern similar to a water jump, such as a tumbling flow or a smiling flow, is formed. The water surface of the rapid flow gradually decreases, and then the water depth increases rapidly after a certain lowest position (contracted water depth), and the flow velocity decreases significantly.

[0135] When the slow flow turns into the rapid flow, a water drop will occur, the water level will drop suddenly, and the flow rate will increase significantly;

[0136] Rapids and slow flows do not just alternate upstream and downstream. At the same plane, due to the speed difference between the left and right sides, the rapids and slow flows shear to form a vortex, making the water level flow velocity at the center of the vortex low and the water exchange volume small.

[0137] The boiling flow 21 should be arranged at the upstream or inlet section of the waterway 2; the water surface width should not be less than 8m and the length should not be less than 10m. The boiling flow 21 water-blocking structure can adopt a broken line weir type. A permeable platform can be arranged upstream according to training requirements to supply water to the waterway 2, and the elevation should be flush with the weir top. The total drop of the upstream and downstream water surfaces is controlled at 0.8m~1.5m, the water velocity of the drop or jet is 4m / s~6m / s, and the water entry angle is not greater than 60°. The outer surface velocity within 5m of the boiling flow 21 water entry point should be less than 2m / s.

[0138] The frown flow 25 is preferably arranged at the side wall of the curved section or straight section. The obstacle arrangement direction of the frown flow 25 is perpendicular to the water flow or points to the center of the curved section, and the width is 1 / 3B. 皱 ~1 / 2B 皱 Among them, B 皱 The width of the waterway in the frown flow section, the vertical inclination angle of the obstacle facing the water is 60°~90°. The water depth of the obstacle facing the water surface is greater than 0.6m, and the flow velocity is not greater than 2m / s. The water depth of the frown flow 25 should be 0.2m~0.5m lower than the top of the obstacle.

[0139] The V-shaped flow 22 is preferably arranged in a straight line segment, such as Figure 2 The obstacle direction of the V-shaped flow 22 shown can be perpendicular to the water flow, and the turning radius R is ; or arranged diagonally downstream, the end of the obstacle should not face upstream. The vertical projection width of the V-shaped flow is 1 / 3B v ~1 / 2B v , where B v The width of the V-shaped flow channel, the flow velocity at the tip is greater than 3m / s, the flow velocity on both sides is less than 2m / s, and the water depth on both sides is greater than 0.6m. The water-facing surface of the inverted V-shaped flow obstacle should be a flat surface or a smooth curved surface, with a width of 1 / 6B v ~1 / 4B v , the radius of curvature is not less than 1m, the width of the back water surface is 1 / 3B v ~1 / 2B v , the flow velocity on both sides is greater than 2m / s, and the water depth is greater than 0.6m.

[0140] The tumbling flow should be arranged at the downstream of waterway 2 or the straight section of the outlet, with a length greater than 10m and a width greater than 4m. The tumbling flow training area is divided into an acceleration area and a tumbling area. The acceleration area should be a smooth steep slope, the water depth should not be less than 0.2m, and the flow rate should be greater than 4m / s. The tumbling area should be flat or reverse slope, and the water depth should be greater than 0.8m.

[0141] Smiling flow27 is essentially a kind of flow around the obstacle, and a vortex is formed behind the flow obstacle, namely the Karman vortex. The formation of the Karman vortex is related to the Reynolds number. Figure 3 As shown in , different vortices will be formed in different Reynolds number ranges; Figure 4 Shown is the perimeter of the smiling flow through the water profile;

[0142] The obstacles in the smiling flow 27 should be arranged in the middle of the straight line segment, with the direction of the obstacles perpendicular to the direction of the water flow, and the bottom slope of the smiling flow 27 should be flat or gentle. The vertical inclination angle of the water-facing surface is 60°~90°, and the width of the two sides of the smiling flow waterway is B. 微 , smiling flow obstacle width 1 / 3B 微 ~1 / 2B 微 , the length or thickness along the water flow direction is greater than 0.4m. The stable water depth on the back of the obstacle should be greater than 0.6m, the backflow velocity should be less than 1.5m / s, and the water surface width of the back training area should be no less than 6m and the length should be no less than 8m.

[0143] When the vortex flow 24 is arranged in a curved section, it is advisable to arrange the obstacle on the inner side of the curve, with the direction pointing to the center of the arc outside the curve; when arranged in a straight section, a concave area (concave bank) can be set on one side of the straight section, or an obstacle can be arranged opposite the concave area to enhance the rotation of the water flow. The width of the concave area is set to 1 / 2B 漩 ~3 / 2B 漩 , where B 漩 is the width of the vortex flow channel; when an obstacle is added opposite the concave area to enhance the vortex effect, the length of the obstacle is 1 / 2B 漩 ~1B 漩 ; Length of vortex obstacle in the curve area 1 / 3B 漩 ~1 / 2B 漩 ; The flow velocity at the outer edge of the vortex is 1.5m / s~3m / s, the flow velocity in the single-person training area should not be greater than 2m / s, and the water depth should not be less than 0.6m.

[0144] The transition zone can be arranged between each designed flow channel, for example, a transition zone is arranged between the boiling flow 21 and the frowning flow 25. The transition zone is not marked in the attached figure; a transition zone should be arranged downstream of the V-shaped flow 22 and the smiling flow 27. If the tumbling flow and the covering flow 26 are not arranged at the end of the waterway 2, a transition zone should also be arranged downstream thereof. The bottom slope of the transition zone should be a hydraulic gentle slope or a flat bottom, and the front and rear width of the section should be kept at 1B. 渡 , no obstacles are set in the middle.

[0145] Computational area and grid division:

[0146] Considering that this project involves obstacles of various shapes and the geometric model is very complex, mesh division is suitable for unstructured meshes with good adaptability. If unstructured meshes are used, the number of meshes will reach 3.5 million. The huge number will lead to problems such as slow calculation and excessive calculation files, and even the phenomenon that the results cannot be opened. Therefore, a hybrid mesh combining structured and unstructured meshes is adopted. Structured meshes are mainly used in the straight sections of the waterway, the water inlet pool, the boiling pool and the outlet stilling pool area. Unstructured meshes are used on the edge of the guide wall and the obstacle area of ​​the waterway, and the meshes are locally encrypted at necessary locations. The minimum mesh is 0.03m, the maximum is 0.35m, the number of meshes is 930,000, and the number of mesh nodes is 460,000;

[0147] According to the commonly used roughness values ​​in hydraulic calculations in the Spillway Design Code, the type of water flow side wall and its surface characteristics are: smooth ceramic tiles, and its roughness n value is about 0.013.

[0148] Mathematical model control equations:

[0149] The RNG k-ε model is used to simulate turbulence. Compared with the standard k-ε model, its main changes are: (1) by modifying the turbulent kinetic energy viscosity, the rotation and swirl flow in the average flow are taken into account; (2) an additional term is added to the ε equation to reflect the time-averaged strain rate of the mainstream. Therefore, the term generated in the RNG k-ε model is not only related to the flow conditions, but also a function of the spatial coordinates in the same problem. Therefore, this turbulence model can better handle flows with high strain rates and large streamline curvature.

[0150] In the RNG k-ε model, these small-scale motions are systematically removed from the governing equations by reflecting the effects of the large-scale motions and the modified viscosity terms. The resulting k- and ε-equations are very similar to those of the standard k-ε model.

[0151] Continuity equation:

[0152] (3-1)

[0153] Momentum equation:

[0154] (3-2)

[0155] in, , represents density, represents the molecular dynamic viscosity, t represents time, and are velocity components, is the corrected pressure, represents the viscous stress tensor, represents the coordinate components, represents the gravitational body force, represents the external body force.

[0156] Turbulent kinetic energy equation:

[0157] (3-3)

[0158] Dissipation rate equation:

[0159] (3-4)

[0160] in, , is the turbulent viscosity coefficient, , , , , , , , , , . and They are and The turbulent Prandtl number, , . and is the model constant, , , , . is the turbulent kinetic energy caused by the mean velocity gradient The generated items, .

[0161] VOF model:

[0162] Water flow with free surface is a very common natural phenomenon. How to track and simulate the free surface has always been the focus of numerical simulation research. In this paper, only the gas-liquid two-phase flow and volume fraction equation are used:

[0163] (3-5)

[0164] In the formula, and are the volume fractions of air and water, respectively, and are the densities of air and water, respectively, and are the kinematic viscosity coefficients of air and water, respectively. In the control body, It means that there is no water in the volume unit and it is filled with air only; It means that there is no gas in the volume unit and it is filled with water only; It means that there is both water and gas in the volume unit.

[0165] Tracking of the water-air interface is accomplished by solving the following continuity equation:

[0166] (3-6)

[0167] according to The value of can be used to know the distribution position of the free surface.

[0168] The main flow characteristics of boiling flow 21 are as follows: the water flows into the downstream water body in the form of a drop flow or a pick flow. Under the shear and drag of the water flow, the downstream water body forms a fast-moving surface transverse axis vortex, forming a tumbling flow similar to a "drum washing machine". At the same time, the water flow carries a large amount of air, causing a large amount of aeration inside the water body, with the air content reaching 40% to 50%. The water body density is reduced, and the buoyancy is significantly reduced. People in distress are easily locked in the vortex area due to the drag of the water flow and insufficient buoyancy, and it is difficult for them to escape by themselves. This is the most commonly encountered extremely dangerous water flow;

[0169] Usually, the vertical morphology of the boiling zone contains a vortex. Since there is only one vortex, the water body has relatively little exchange in the vertical direction. After passing through a vortex, the kayak or floating object enters the downstream area. The vortex has a small impact range and the training space is relatively limited.

[0170] In order to enhance the rapid up-and-down reciprocating movement of the boiling flow 21, the boiling flow 21 adopts a scoop design, and an adjustment sill is designed at the bottom of the boiling zone. After the water flow dives into the pool bottom, it jumps to the water surface again with the help of the sill, and forms vertical vortexes in opposite directions on the upstream and downstream sides respectively. The upstream vortex dives to the pool bottom again under the action of falling water, and then forms a third vortex between the landing point and the upstream pool wall. The upper part of the downstream vortex continues to move downward along the waterway, and a part of it dives rapidly after being blocked by the downstream pool wall. If the floating objects on the water surface have a deep draft, they are easily rolled into the pool bottom.

[0171] From the perspective of cross-sectional flow, the vertical shape of the boiling flow 21 changes from one vortex to three vortices, the aeration effect of the water body is significantly improved, and the buoyancy of the water body will also be reduced. The upstream side of the landing point is easy to be drawn in, and floating objects are difficult to escape. The water body movement on the downstream side of the landing point is up and down, which is difficult to control.

[0172] In practical applications, the water level at the outlet of boiling flow 21 has a greater impact on the boiling flow. When conducting boiling flow 21 training content, it is advisable to reduce obstacles close to the downstream of boiling flow 21.

[0173] The vortex flow 24 of the existing waterway 2 expansion section is too narrow and long. A wider smiling flow obstacle and a semi-enclosed vertical obstacle are set in this area to strengthen the streamline twisting and water body shearing. Through comparative analysis, the semi-enclosed vertical obstacle is adopted, and the effect is more prominent.

[0174] The existing flow state of the covering flow 26 is difficult to achieve. Setting the covering flow 26 at the outlet section of the waterway 2 with a Froude number Fr ranging from 1 to 1.7 can better achieve the covering flow 26 effect.

[0175] Each flow pattern zone is not single and independent. The smiling flow 27 flow pattern is a planar effect, and the frowning flow 25, tumbling flow, and covering flow 26 flow patterns are longitudinal section flow patterns. Various flow patterns can often be arranged in combination. Among them, the smiling 27 flow obstacle is often arranged in the river, and a small backflow vortex is formed on the back water surface. The water level can be raised on the front water surface. It can be arranged downstream of the rapids to form a covering flow 26 or a tumbling flow. Therefore, the recommended solution flow pattern distribution diagram lists only the main distribution flow patterns. Depending on the flow rate or water depth, the same obstacle may produce different flow patterns.

[0176] A transition zone should be arranged between flow patterns. The length of the transition zone can be calculated by multiplying the flow velocity and the reaction time. It takes about 3 seconds to react from a sudden fall or collision to judging the situation and taking action. Since the local flow velocity can reach up to 7m / s, a 20m interval can ensure sufficient reaction time to deal with the next dangerous waters. Secondly, swimming in rapid waters consumes a lot of physical energy. If you pass through multiple intense flow channels continuously without enough rest areas, you are prone to physical exhaustion or even drowning. Therefore, the flow patterns of intense flow channels cannot be arranged closely. There must be a transition zone in the middle to rest and ensure safety. In addition, various design standards comprehensively consider the flow velocity limit and the size of the interval, which is also convenient for implementing rescue guidance. If the flow patterns are arranged continuously, it is difficult to implement boat and boat close-fitting guidance rescue. Therefore, the 10~20m interval is a safety measure to adjust the transition and take into account physical recovery.

[0177] The design requirements are as follows:

[0178] 1. Boiling flow 21: Boiling flow 21 should be arranged at the upstream or inlet section of waterway 2; the water surface width should not be less than 8m and the length should not be less than 10m. The water-blocking structure of boiling flow 21 can adopt the type of broken line weir. The upstream can be arranged with a permeable platform according to the training requirements, and the elevation should be flush with the top of the weir. The total drop of the upstream and downstream water surfaces is controlled at 0.8m~1.5m, the water velocity of the drop flow or jet flow is 4m / s~6m / s, and the water entry angle is not greater than 60°. The outer surface velocity within 5m of the boiling flow 21 water entry point should be less than 2m / s.

[0179] 2. Smiling Flow 27: The obstacles in Smiling Flow 27 should be arranged in the middle of the straight line, with the direction of the obstacles perpendicular to the direction of the water flow, and the bottom slope should be flat or gentle. The vertical inclination angle of the waterfront surface is 60°~90°, with the width of both sides of the waterway as B.微 , the obstacle width of smiling flow 27 is 1 / 3B 微 ~1 / 2B 微 , the length or thickness along the water flow direction is greater than 0.4m. The stable water depth on the back of the obstacle should be greater than 0.6m, the backflow velocity should be less than 1.5m / s, and the water surface width of the back training area should be no less than 6m and the length should be no less than 8m.

[0180] 3. Frowning flow 25 + vortex flow 24: The obstacles in the bend vortex flow 24 are adjusted to be perpendicular to the water flow direction. After the water flow enters the bend vortex flow 24, a part of the left side impacts the obstacles and disperses to both sides, forming a small counterclockwise vortex on the left side, and merging with the mainstream on the right side to enter the bend vortex area, and forming a clockwise return flow at the sudden expansion position of the waterway, forming a larger vortex flow at the northwest corner bend. From the distribution of traces, the vortex has better closure and is closer to a circle than other schemes. The vortex diameter is about 6m, which can provide a more spacious vortex training space to achieve the purpose of multi-person training. The flow velocity at the center of the vortex is 0.5m / s, and the flow velocity at the outer edge of the vortex is 1~1.5m / s.

[0181] 4. Frowning flow 25: Frowning flow should be arranged at the side wall of the curved section or straight section.

[0182] like Figure 5 As shown, when the frown flow 25 is arranged in the bend section, the obstacle is arranged outside the bend section and the obstacle arrangement direction is perpendicular to the water flow or points to the center of the bend, with a width of 1 / 3B 皱 ~1 / 2B 皱 , the vertical inclination angle of the obstacle facing the water is 60°~90°. The water depth of the obstacle facing the water is greater than 0.6m, and the outermost flow velocity is no more than 2m / s. The water depth should be 0.2m~0.5m lower than the top of the obstacle;

[0183] Due to the centrifugal force, the water flow velocity on the outside of the curved section (thick arrow) is greater than the water flow velocity on the inside (thin arrow), making the outside of the curved section of the frown flow 25 an intense area and the inside a relaxing area. When the trainees are training in front of obstacles in the intense area, they consume more physical energy. When the trainees walk to the relaxing area on the inside, the flow velocity is lower and it can serve as a temporary rest area.

[0184] The frown flow 25 has certain requirements on the water depth. If the depth is too small, it cannot meet the training requirements. Under the premise of unchanged flow rate, the greater the water depth, the lower the flow rate. If the flow rate is too low, the training effect cannot be achieved. Therefore, the frown flow 25 can be arranged in the bend section to concentrate the flow rate on the outside of the bend section. The inner side with low flow rate can be used as a rest area to improve safety.

[0185] Furthermore, when the frown flow 25 is connected to a gentle flow channel upstream, the flow velocity of the frown flow 25 can be increased by arranging it in a curved section.

[0186] 5. Vortex 24: Figure 6 As shown, when the vortex flow 24 is arranged in the bend section, the width of the waterway does not need to be widened. It is better to arrange the obstacle on the inside of the bend, with the direction pointing to the center of the arc outside the bend; the length of the vortex flow obstacle in the bend area is 1 / 3B 漩 ~1 / 2B 漩 ; A fierce flow channel, such as a V-shaped flow, can be connected upstream of the vortex flow 24. Since the V-shaped flow concentrates the flow velocity in the middle, the faster flow velocity in the middle cooperates with the vortex flow obstacle in the bend area to achieve a fast flow velocity on the outside of the bend and a slow flow velocity on the inside to form a vortex;

[0187] The flow velocity at the outer edge of the vortex is 1.5m / s~3m / s, the flow velocity in the single-person training area should not be greater than 2m / s, and the water depth should not be less than 0.6m.

[0188] Usually, when the vortex flow 24 is arranged in a straight section, it needs to be widened. A concave area (concave bank) can be set on one side of the straight section, or obstacles can be arranged opposite the concave area to enhance the rotation of the water flow. Width of concave area 1 / 2B 漩 ~3 / 2B 漩 ,This setting has a relatively poor vortex effect formed in the concave area;

[0189] like Figure 7 As shown, when an obstacle is added opposite the concave area to enhance the vortex effect, the length of the obstacle is 1 / 2B 漩 ~1B 漩 Two vortices with opposite directions are formed by the cooperation of the recessed area and the obstacle, and the effects of the two vortices are obviously better than the vortex in the recessed area without obstacles.

[0190] 6. White water area 28: Multiple groups of independent single obstacles are arranged to enhance the aeration effect of the water body, and a more obvious backflow is formed on the outer edge of the V flow. The flow rate of this white water area is less than 2m / s, which is suitable for corresponding kayak control training.

[0191] 7. Tumbling flow: Tumbling flow should be arranged at the downstream of waterway 2 or the straight section of the outlet. The arrangement of the curved section needs to be verified by model test. The length should be greater than 10m and the width should be greater than 4m. The tumbling flow training area is divided into an acceleration area and a tumbling area. The acceleration area should be a smooth steep slope, the water depth should not be less than 0.2m, and the flow rate should be greater than 4m / s. The tumbling area should be flat or reverse slope, and the water depth should be greater than 0.8m.

[0192] 8. V-shaped flow 22: V-shaped flow 22 should be arranged in a straight line, and the direction of the obstacle can be perpendicular to the water flow; or arranged diagonally downstream, and the end of the obstacle should not face the upstream direction. The projection width of V-shaped flow 22 perpendicular to the water flow is 1 / 3B V~ 1 / 2B V, the tip flow velocity is greater than 3 m / s, the flow velocities on both sides are less than 2 m / s, and the water depths on both sides are greater than 0.6 m. The water-facing surface of the inverted V-flow obstacle should preferably be a plane or a smooth curved surface, with a width of 1 / 6B v ~1 / 4B v , the radius of curvature is not less than 1 m, and the width of the water-backing surface is 1 / 3B v ~1 / 2B v , the flow velocities on both sides are greater than 2 m / s, and the water depth is greater than 0.6 m.

[0193] 9. Covering flow 26: It should preferably be distributed from the outlet of the water channel 2 to the outlet of the stilling basin, with obvious vortex flows formed on both sides, and the vortex flow velocity is 0.5 - 1 m / s.

[0194] 10. Transition zone: The transition zone can be arranged between various designed flow patterns. A transition zone should be arranged downstream of the V-shaped flow 22 and the smiling flow 27. If the tumbling flow and the covering flow 26 are not arranged at the very end of the water channel, a transition zone should also be arranged downstream of them. The bottom slope of the transition zone should preferably be a hydraulic mild slope or a flat bottom, and the width of the cross-section should preferably remain 1B 渡 , and no obstacles should be set in the middle.

[0195] The above-described embodiments only represent the specific implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for designing a safe water rescue training structure, characterized in that: include: Establish a mathematical model of the water rescue training structure, which includes the water inlet pool, waterway and outlet stilling pool; Meshing and boundary condition processing; The water channel includes an intense flow channel and a gentle flow channel which are alternately connected in sequence, and obstacles are arranged in the intense flow channel and / or the gentle flow channel; The RNG k-ε model is used to simulate the turbulent flow starting from the inlet pool, passing through the waterway and finally flowing to the outlet stilling pool; The compressible gas-water two-phase transient flow is described by the VOF model; Calculate the flow pattern, water level and flow velocity of each intense flow channel and gentle flow channel at each design flow rate of the waterway to see whether they meet the design requirements; If the design requirements are not met, adjust at least one of the obstacle size, obstacle combination or waterway bottom slope until the design requirements are met; The intense flow path is boiling flow, frowning flow, V-shaped flow, tumbling flow or white water area; the gentle flow path is covering flow, smiling flow, transition zone or vortex flow; The design requirements are as follows: The flow velocity of the outer surface within 5m of the boiling water inflow point is less than 2m / s; The stable water depth behind the obstacle of the smiling flow is greater than 0.6m, and the backflow velocity is less than 1.5m / s; The flow velocity at the center of the frown flow + vortex flow is 0.5 m / s, and the flow velocity at the outer edge of the vortex is 1~1.5 m / s; The water depth on the front side of the frown flow obstacle is greater than 0.6m, and the outermost flow velocity is no more than 2m / s; When the vortex flow is arranged in the bend section, the flow velocity at the outer edge of the vortex is 1.5m / s~3m / s, the flow velocity in the single-person training area is not more than 2m / s, and the water depth is not less than 0.6m; The flow rate of white water is less than 2m / s; The tumbling flow training area is divided into an acceleration area and a tumbling area. The water depth in the acceleration area is not less than 0.2m and the flow velocity is greater than 4m / s. The tumbling area is flat or reverse slope with a water depth greater than 0.8m. The velocity at the tip of the V-shaped flow is greater than 3m / s, the velocity on both sides is less than 2m / s, and the water depth on both sides is greater than 0.6m. The velocity on both sides of the inverted V-shaped flow obstacle is greater than 2m / s, and the water depth is greater than 0.6m. Obvious vortex flow is formed on both sides of the covering flow, with a vortex flow speed of 0.5~1m / s.

2. A method for designing a safe water rescue training structure according to claim 1, characterized in that: The design method of the boiling flow is as follows: Calculate boiling flow rate per width q 沸腾 : Among them, Q is the water supply capacity of the waterway pump, m 3 / s; B 沸腾 is the boiling flow channel width, m; boiling flow single width flow rate q 沸腾 , m 3 / (s·m); According to the boiling flow single width flow q 沸腾 Preliminary assessment of water head over boiling flow weir : calculate Size, select the quick calculation formula of water head H on boiling flow weir according to the corresponding range: Where δ is the thickness of the top of the water head on the boiling flow weir, m; Boiling flow length L 沸 , calculated by the number of training boats: L 沸 =10+N L 艇 ; Among them, 10 is the unit of length, m; L 艇 is the length of the training boat, m; N is the number of training boats.

3. A method for designing a safe water rescue training structure according to claim 1, characterized in that: The waterway (2) has at least one bend. When the frown flow is arranged at the bend, the obstacle is arranged outside the bend and the obstacle arrangement direction is perpendicular to the water flow or points to the center of the bend. The method for calculating the height of the obstacle inside the bend is as follows: Among them, H 外 Design height of the outer obstacle of the frown flow curve section, m; H 皱均 is the average water depth of the Frown Flow Bend, m; V 皱 is the flow velocity of the frown flow bend, m / s; B 皱 is the width of the frown flow bend, m; R 皱 is the bend radius of the outer edge of the frown flow bend, m; g is the acceleration due to gravity, m / s 2 .

4. A method for designing a safe water rescue training structure according to claim 1, characterized in that: The calculation method of the V-shaped flow water surface height and the V-shaped flow obstacle height is as follows: When obstacles in a V-shaped flow are placed perpendicular to the direction of the water flow, the water surface is raised. Calculated using the following formula: Obstacles to V-shaped flow The height calculation formula is: Among them, H V均 is the average water depth of the V-shaped flow section, m; v is the flow velocity of water in the V-shaped flow section, m / s.

5. The method for designing a safe water rescue training structure according to claim 1, characterized in that: The tumbling flow increases the flow velocity by utilizing the steep slope and reducing the cross-sectional width, the flow velocity is greater than 4 m / s, and the contraction width is less than 1 / 2B 翻 , where B 翻 is the width of the tumbling waterway, and the steep slope ratio is 1:5~1:10; The tumbling flow slope bottom is connected to the flat bottom, and the downstream tumbling flow is deep Calculated according to the conjugate water depth formula: Among them, Fr1 is the Froude number of the tumble flow contraction section, and Fr1 is greater than 2.5; h1 is the water depth of the contraction section of the tumbling flow, h1 is greater than 0.2m; Tumble flow length calculation formula: When L 翻 <10, take L 翻 =10m.

6. A method for designing a safe water rescue training structure according to claim 1, characterized in that: The smiling flow obstacle forms backflow on the water-facing side and vortex backflow on the water-receiving side. The size parameters of the smiling flow obstacle are controlled by the following formula: Among them, V 微 L is the flow velocity of the upstream water flow in the smiling flow, m / s; 微 L is the length of the smiling flow obstacle perpendicular to the water flow direction, m; 微 Value 1 / 3B 微 ~1 / 2B 微 , B 微 is the width of the smiling waterway, m; the formula is applicable to water temperatures of 10℃~20℃; h 微 is the water depth of the smiling flow section, m.

7. A method for designing a safe water rescue training structure according to claim 1, characterized in that: The vortex flow is adjusted according to the training intensity. The width of the vortex flow area is greater than 8m. The vortex flow effect is affected by the running flow rate. The vortex flow velocity is high and the water flow is in a torrent state. At this time, the minimum single width flow rate q of the upstream waterway of the vortex flow is 漩 Calculated using the following formula: When the water depth h 漩 When the minimum value is 0.6m, q 漩 =1.455m³ / (s·m); The vortex flow rate is: Q 漩 The traffic volume for single-person training should not exceed 1.455B. 漩 If the training water depth increases, adjust Q according to the above formula 旋 size; Among them, Q 漩 is the flow rate of the vortex flow section, m 3 / s; B 漩 is the width of the vortex flow channel, m; h 漩 is the water depth of the vortex flow section, m.

8. A method for designing a safe water rescue training structure according to claim 1 or 7, characterized in that: The water channel (2) has at least one bend, and when the vortex flow is arranged at the bend, the internal obstacle is arranged on the inner side of the bend, and the upstream of the vortex flow at the bend is connected to a violent flow channel with a flow velocity concentrated in the middle; or When the vortex flow is arranged at the straight position, a recessed area is arranged on one side of the straight, and an obstacle is arranged in the middle of the other side opposite to the straight.

9. A method for designing a safe water rescue training structure according to claim 1, characterized in that: The transition zone is arranged between each flow state, and the minimum length of the transition zone is L 渡 Calculated based on the maximum upstream flow velocity: Among them, V max is the maximum flow velocity upstream of the transition zone, m / s; 3 is the time unit, seconds; when L 渡 When the calculated value is less than 10m, L 渡 =10m.

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