A method for calculating the height of a tidal bore in a non-high-frequency tidal level sequence

Abstract

The present invention discloses a method for calculating the height of a tidal bore in a non-high-frequency tidal level sequence, comprising the following steps: S1, determining the calculation parameters of the first non-high-frequency tidal level sequence: time interval dt0, number of tides N0, and per-tide water depth turbulence g; S2, obtaining the first high-frequency tidal level sequence of the study area; S3, statistically calculating the per-tide height of the tidal bore H0 of the first high-frequency tidal level sequence; S4, resampling the first high-frequency tidal level sequence to obtain a second non-high-frequency tidal level sequence; S5, calculating the per-tide water depth turbulence g of the second non-high-frequency tidal level sequence; S6, establishing a correlation relationship based on the per-tide height of the tidal bore H0 of the first high-frequency tidal level sequence and the per-tide water depth turbulence g of the second non-high-frequency tidal level sequence; S7, substituting the water depth turbulence g determined in S1 into the correlation relationship established in S6 to estimate the height of the tidal bore H0. The present invention can reflect the differences in the intensity of the tidal bore caused by different local water depths, can more accurately estimate the height of the tidal bore in the study area, and is also more in line with the actual situation.

Description

Technical Field

[0001] The present invention relates to the field of river regulation engineering, and particularly to a method for determining the tidal bore intensity in the areas where seawalls, cofferdams, groynes, bridge piers, sluice gates or other water-related projects are located. Background Art

[0002] A tidal bore is the rising tide stage after a tidal wave enters an estuary, where the water level suddenly rises within a few seconds and over a range of more than ten meters, belonging to a special shallow water discontinuous flow motion. A tidal bore is a valuable natural resource and at the same time a special strongly nonlinear discontinuous flow motion containing huge energy, with large flow velocity, strong destructive power and complex flow characteristics. When a tidal bore passes by, structures such as seawalls, cofferdams, groynes, bridge piers and gates on both banks will be slapped by the tidal bore, and the huge force generated instantaneously is likely to cause the instability of water-related projects. The tidal bore height is one of the main indicators for measuring the tidal bore intensity. The greater the height, the stronger the tidal bore and the greater the safety threat to related buildings. Therefore, obtaining the tidal bore height plays a very important role.

[0003] Generally speaking, the tidal bore height refers to the water level difference before and after the tidal bore front, that is, the height difference between the top surface of the water heap (excluding the water spray) of the tidal bore front and the low water level of the front toe of the tidal end. Because the process of a strong tidal bore front generally lasts only a few seconds, currently the tidal bore height generally needs to be obtained through high-frequency tide level monitoring data (with a time interval of about 1 s). Traditionally, the time interval of tidal level observation data is generally several minutes to 1 h, all belonging to non-high-frequency tide level data (with a time interval of 1 minute and above), and generally the tidal bore height data cannot be directly read. For non-high-frequency tide level data, currently it is mainly converted by the simple linear correlation relationship between the local historical tidal bore height and the corresponding tidal range. For example, for a certain tidal bore reach, the relationship between the fitted tidal bore height H0 and the tidal range Tr is: H0 = 0.84*(Tr - 0.12). However, this method does not consider the difference in the tidal bore turbulence effect caused by different local water depths in the same reach; in the same reach, the tidal range is basically unchanged, but the water depth difference between the shore and the main channel of the river is large, and the tidal bore turbulence effect difference is obvious, resulting in a large difference in the tidal bore height. Therefore, using the tidal range Tr to calculate the tidal bore height for both the beach and the trough is often the same, which is significantly different from the measured data. The calculated tidal bore height is often too small in the shallow water area and too large in the deep water area. Summary of the Invention

[0004] The traditional empirical formula method for determining the tidal bore height of non-high-frequency tide levels cannot be applied to the difference in the tidal bore turbulence effect caused by the difference in local water depths in the same reach, and the calculation results are too small in the shallow water area and too large in the deep water area. In view of the above problems, the present invention proposes a method for calculating the tidal bore height considering the tidal bore level turbulence effect, which improves the calculation accuracy of calculating the tidal bore height based on non-high-frequency tide level sequences.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for calculating the height of a tidal bore in a non-high-frequency tidal level sequence, comprising the following steps:

[0007] S1. Define the sequence as the first non-high-frequency tidal level sequence, and determine the calculation parameters of the sequence: the time interval dt0, the number of tides N0, and the water depth turbulence g; dt0 is the time interval between adjacent tidal level data in the tidal level sequence, generally 1-10 min; the number of tides N0 is the total number of tidal level processes including complete flood tides and ebb tides in the sequence, N0≥1; the water depth turbulence g is the ratio of the standard deviation of the pulsating water depth to the time-average water depth, and the calculation formula is shown in Equation (1), which is used to quantitatively represent the strength of water depth fluctuations:

[0008]

[0009] In the formula, ξ is the instantaneous water depth, ξ = η - Z, η is the instantaneous tidal level, and Z is the riverbed elevation;

[0010] is the time-average water depth, is the time-average tidal level;

[0011] is the pulsating water depth, is the pulsating tidal level;

[0012] i is the tidal level data count, n is the total number of tidal level data within the statistical time interval, and g is the water depth turbulence;

[0013] S2. Collect the historical high-frequency tidal level process of the research area, or re-measure the high-frequency tidal level process of this area to obtain the first high-frequency tidal level sequence;

[0014] S3. For the first high-frequency tidal level sequence collected in step S2, count the height of the tidal bore H0 for each tidal process according to the definition of the height of the tidal bore;

[0015] S4. For the first high-frequency tidal level sequence in step S2, re-sample according to the time interval dt0 of the first non-high-frequency tidal level sequence to form the second non-high-frequency tidal level sequence;

[0016] S5. Calculate the water depth turbulence g for each tide in the second non-high-frequency tidal level sequence in step S4;

[0017] S6. Establish a correlation relationship based on the height of the tidal bore H0 of the first high-frequency tidal level sequence in step S3 and the water depth turbulence g of the second non-high-frequency tidal level sequence in step S4 to obtain the relationship formula for calculating the height of the tidal bore H0 from the water depth turbulence g:

[0018] H0 = a*f(g) + b (2)

[0019] Wherein, a and b are coefficients; f(g) is a function of the turbulence intensity g, and one of a logarithmic, exponential or linear function is selected according to the strength of the correlation;

[0020] S7. Using the relationship H0 = a*f(g) + b determined in step S6, substitute the water depth turbulence intensity g of each tidal process in the first non-high-frequency tidal level sequence obtained in step S1 to obtain the corresponding tidal bore height H0. Repeat this process and obtain the tidal bore heights H0 corresponding to all the tidal numbers N0 in the first non-high-frequency tidal level sequence.

[0021] Further, in step S1, when determining the water depth turbulence intensity g, the statistical time interval of the average water depth is set to 60 min.

[0022] Further, in step S2, the first high-frequency tidal level sequence needs to contain 5 or more complete tidal level processes including tidal bores.

[0023] Further, in step S6, the specific logarithmic function correlation relationship selected is: H0 = 2.93*ln(g) + 4.2, where the coefficient a = 2.93 and b = 4.2.

[0024] Further, in step S6, the specific linear function correlation relationship selected is: H0 = 6.52*g - 1.16, where the coefficient a = 6.52 and b = -1.16.

[0025] Further, in step S6, the specific exponential function correlation relationship selected is: H0 = 0.27e 4.0*g , where the coefficient a = 0.27 and b = 0.

[0026] The beneficial effects of the present invention are:

[0027] The present invention considers the influence of the tidal level turbulence effect on the tidal bore height, overcomes the deficiency of calculating the tidal bore height only through the tidal range in the past, ignores the difference in the beach trough turbulence effect, and is often too small in the shallow water area and too large in the deep water area, and improves the calculation accuracy of calculating the tidal bore height. Description of the Drawings

[0028] Figure 1 is a calculation flow chart;

[0029] Figure 2 is a schematic diagram of the definition of the tidal bore height and the tidal process;

[0030] Figure 3 is a schematic diagram of resampling the high-frequency tidal level process;

[0031] Figure 4 is a schematic diagram of the logarithmic function correlation relationship between the water depth turbulence intensity and the tidal bore height;

[0032] Figure 5 Schematic diagram of the linear function correlation between water depth turbulence and tidal bore height;

[0033] Figure 6 Schematic diagram of the exponential function correlation between water depth turbulence and tidal bore height. Specific implementation manners

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0035] [Embodiment 1]

[0036] A method for calculating the tidal bore height of a non-high-frequency tidal level sequence according to the present invention is based on Figure 4 the logarithmic correlation between water depth turbulence and tidal bore height, and includes the following steps, as Figure 1 shown:

[0037] Given the measured tidal level sequences of two stations in the deep water area (riverbed elevation 2.2 m) and the shallow water area (riverbed elevation 3.0 m) of a certain tidal bore reach from 9-23 0:00 to 9-23 23:00 with a time interval of 1 min, and this sequence has a total of 4 complete tidal processes, it is necessary to deduce the tidal bore height corresponding to each of these 4 tidal processes:

[0038] S1. Determine the calculation parameters of the first non-high-frequency tidal level sequence;

[0039] Define the tidal level sequence for which the tidal bore height is to be determined as the first non-high-frequency tidal level sequence, and determine the time interval dt0, the number of tides N0, and the water depth turbulence g of each tide: In this example, the time of the target tidal level process to be determined is 1 min, and it is necessary to calculate the tidal bore heights of 2 in the deep water area and 2 in the shallow water area, a total of 4 complete tidal processes. Therefore, dt0 = 1 min, N0 = 4; the water depth turbulence of each tidal process is calculated by Equation (1): First, subtract the riverbed elevation from each tidal level value to obtain the water depth, and the statistical time interval of the average water depth is set to 60 min, so that the ratio of the standard deviation of the pulsating water depth to the time-averaged water depth during the flood tide process can be calculated, which is the water depth turbulence g of the corresponding tidal process. The calculation conditions and results are shown in Table 1:

[0040] Table 1 Tidal-by-tidal water depth turbulence of the first non-high-frequency tidal level sequence in a certain tidal bore reach

[0041]

[0042] S2. Obtain the first high-frequency tidal level sequence;

[0043] Collect historical high-frequency tidal level process data for the study area or conduct new high-frequency tidal level measurements to obtain the first high-frequency tidal level sequence. In this example, high-frequency tidal level process data with a time interval of 1 s from 0:00 on September 24 to 23:00 on September 27 at two stations in the same location as the first non-high-frequency tidal level sequence are collected as the first high-frequency tidal level sequence. The number of tides at the deep-water station in this sequence is 8, and the number of tides at the shallow-water station is 4, as shown in Appendix 2.

[0044] S3. Statistically analyze the surge height of the first high-frequency tidal level sequence.

[0045] According to Figure 2 the defined surge height shown, statistically analyze the surge height of the first high-frequency tidal level sequence tide by tide. The statistical results are also listed in Appendix 2:

[0046] Appendix 2 Measured Surge Heights of the First High-Frequency Tidal Level Process in a Certain Surge-Reaching River Section

[0047]

[0048] S4. Resample the first high-frequency tidal level sequence to obtain the second non-high-frequency tidal level sequence.

[0049] For the first high-frequency tidal level sequence with a time interval of 1 s, resample it according to the time interval dt0 = 1 min of the first non-high-frequency tidal level sequence. As Figure 3 shown, in this way, a second non-high-frequency tidal level sequence with a time interval of dt0 = 1 min is obtained by thinning.

[0050] S5. Calculate the water depth turbulence of the second non-high-frequency tidal level sequence.

[0051] According to the method for calculating the water depth turbulence of the first non-high-frequency tidal level sequence in step S1, calculate the water depth turbulence g of the second non-high-frequency tidal level sequence. The calculation results are listed in Appendix 3:

[0052] Appendix 3 Water Depth Turbulence of the Second Non-High-Frequency Tidal Level Sequence in a Certain Surge-Reaching River Section

[0053]

[0054] S6. Establish a logarithmic function correlation between the surge height and water depth turbulence in the study area.

[0055] For the two columns of data, namely the water depth turbulence of the second non-high-frequency tidal level sequence listed in Appendix 3 and the surge height of the first high-frequency tidal level sequence in Appendix 2, establish a correlation according to the logarithmic function. The fitting situation is as Figure 4 shown. In this example, the logarithmic function relationship for calculating the surge height from the water depth turbulence in the study area is obtained as:

[0056] H0 = 2.93 * ln(g) + 4.2 (3)

[0057] In Equation (3), for the coefficients in Equation (2) \(H_0 = a\times f(g)+b\), \(a = 2.93\) and \(b = 4.2\).

[0058] S7. Calculate the tidal bore height of the first non-high-frequency tidal level sequence;

[0059] Establish the relevant relationship according to Step S6. Substitute the water depth turbulence in Table 1 into Equation (3), and the tidal bore height of each tide number in the first non-high-frequency tidal level sequence can be obtained. The results are shown in Table 4;

[0060] Table 4 Calculated values of tidal bore height by logarithmic function relationship in a certain tidal bore reach

[0061]

[0062] In addition, to compare the effect of this method, the measured tidal bore height, the calculated values obtained by the old relationship \(H_0 = 0.84\times(Tr - 0.12)\), and the calculated values by the logarithmic function relationship in this example are listed in the same column in Table 4. It can be seen that the old relationship \(H_0 = 0.84\times(Tr - 0.12)\) cannot reflect the difference in tidal bore height between the deep water area and the shallow water area of the same river reach. And the result is about 64% larger in the deep water area and significantly smaller in the shallow water area. However, the tidal bore calculated by this method is very close to the measured result, with an average absolute error of about 8%, and it can reflect the differences in tidal bore height at different water depths.

[0063]

Embodiment 2

[0064] A method for calculating the tidal bore height of a non-high-frequency tidal level sequence according to the present invention is based on Figure 5 the linear correlation between water depth turbulence and tidal bore height, and includes the following steps:

[0065] Steps S1 to S5 are exactly the same as those in Embodiment 1 and will not be repeated here;

[0066] S6. Establish a linear function correlation between the tidal bore height and water depth turbulence in the study area;

[0067] Establish a relevant relationship according to the linear function for the two columns of data, namely the water depth turbulence of the second non-high-frequency tidal level sequence listed in Table 3 and the tidal bore height of the first high-frequency tidal level sequence in Table 2. The fitting situation is as Figure 5 shown; in this example, the logarithmic function relationship for calculating the tidal bore height from the water depth turbulence in the study area is:

[0068] \(H_0 = 6.52\times g - 1.16\) (4)

[0069] In Equation (4), for the coefficients in Equation (2) \(H_0 = a\times f(g)+b\), \(a = 6.52\) and \(b = -1.16\);

[0070] S7. Calculate the tidal bore height of the first non-high-frequency tidal level sequence;

[0071] According to the correlation established in step S6, substitute the water depth turbulence in Table 1 into Equation (4), and the tidal bore height of each tide number in the first non-high-frequency tidal level sequence can be obtained. The results are shown in Table 5.

[0072] Table 5 Tidal bore height values calculated by the linear function relationship in a certain tidal bore reach

[0073]

[0074] In addition, to compare the effect of this method, the measured tidal bore height, the calculated value obtained by using the old relationship H0 = 0.84*(Tr - 0.12), and the calculated value of the linear function relationship in this example are listed in Table 5. It can be seen that the old relationship H0 = 0.84*(Tr - 0.12) cannot reflect the difference in tidal bore height between the deep water area and the shallow water area of the same reach, and the result is about 64% larger in the deep water area and significantly smaller in the shallow water area. However, the tidal bore calculated by using this method is very close to the measured result, with an average absolute error of about 9%, and it can reflect the difference in tidal bore height under different water depths.

[0075]

Example 3

[0076] A method for calculating the tidal bore height of a non-high-frequency tidal level sequence according to the present invention is based on Figure 6 the exponential function correlation between water depth turbulence and tidal bore height, and includes the following steps:

[0077] Steps S1 to S5 are exactly the same as those in Example 1 and will not be repeated here;

[0078] S6. Establish an exponential function correlation between the tidal bore height and water depth turbulence in the study area;

[0079] Establish a correlation between the two columns of data, namely the water depth turbulence of the second non-high-frequency tidal level sequence listed in Table 3 and the tidal bore height of the first high-frequency tidal level sequence in Table 2, according to the exponential function. The fitting situation is as Figure 6 shown; in this example, the logarithmic function relationship for calculating the tidal bore height from the water depth turbulence in the study area is:

[0080] H0 = 0.27e 4.0*g (5)

[0081] Formula (5) is when the coefficients in formula (2) H0 = a*f(g) + b take a = 0.27 and b = 0;

[0082] S7. Calculate the tidal bore height of the first non-high-frequency tidal level sequence;

[0083] According to the correlation established in step S6, substituting the water depth and turbulence intensity in Table 1 into Equation (5), the tidal bore height of each tidal number in the first non-high-frequency tidal level sequence can be obtained, and the results are shown in Table 6.

[0084] Table 6 Calculated values of tidal bore height by exponential function relationship in a certain tidal bore reach

[0085]

[0086] In addition, to compare the effect of this method, the measured tidal bore height, the calculated value obtained by the old relationship H0 = 0.84*(Tr - 0.12), and the calculated value of the exponential function relationship in this example are listed in Table 5. It can be seen that the old relationship H0 = 0.84*(Tr - 0.12) cannot reflect the difference in tidal bore height between the deep water area and the shallow water area of the same reach, and the result is about 64% larger in the deep water area and significantly smaller in the shallow water area. However, the tidal bore calculated by this method is very close to the measured result, with an average absolute error of about 7%, and it can reflect the difference in tidal bore height under different water depths.

[0087] The above embodiments describe the present invention with reference to the accompanying drawings, but it should not be construed as limiting the scope 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, the technical solutions obtained by equivalent substitution or equivalent transformation all belong to the protection scope of the present invention.

Claims

1. A method for calculating the height of a tidal bore in a non-high-frequency tidal level sequence, characterized in that: It includes the following steps: S1. Define this sequence as the first non-high-frequency tidal level sequence, and determine the calculation parameters of this sequence: time interval dt0, number of tides N0, and depth turbulence g of each tidal depth; dt0 is the time interval between adjacent tidal level data in the tidal level sequence, generally 1 - 10 min; the number of tides N0 is the total number of tidal level processes including complete flood tides and ebb tides in this sequence, N0≥1; the depth turbulence g is the ratio of the standard deviation of the fluctuating water depth to the time-averaged water depth, and the calculation formula is as shown in Equation (1), which is used to quantitatively represent the intensity of water depth fluctuations: In the formula, ξ is the instantaneous water depth, ξ = η - Z, η is the instantaneous tidal level, and Z is the riverbed elevation; is the time-averaged water depth, is the time-averaged tidal level; is the pulsating water depth, is the pulsating tidal level; i is the count of tidal level data, n is the total number of tidal level data within the statistical time interval, and g is the depth turbulence; S2. Collect the historical high-frequency tidal level process of the research area, or re-measure the high-frequency tidal level process of this area to obtain the first high-frequency tidal level sequence; S3. For the first high-frequency tidal level sequence collected in step S2, statistically calculate the tidal bore height H0 of each tidal process according to the definition of the tidal bore height; S4. For the first high-frequency tidal level sequence in step S2, re-sample according to the time interval dt0 of the first non-high-frequency tidal level sequence to form the second non-high-frequency tidal level sequence; S5. Calculate the depth turbulence g of each tide in the second non-high-frequency tidal level sequence in step S4; S6. Establish a correlation relationship based on the tidal bore height H0 of the first high-frequency tidal level sequence in step S3 and the depth turbulence g of the second non-high-frequency tidal level sequence in step S4 to obtain the relational formula for calculating the tidal bore height H0 from the depth turbulence g: H0 = a*f(g) + b (2) In the formula, a and b are coefficients; f(g) is a function of the turbulence g, and one of the logarithmic function, exponential function, or linear function is selected according to the strength of the correlation; S7. Use the relational formula H0 = a*f(g) + b determined in step S6, substitute the depth turbulence g of each tidal process in the first non-high-frequency tidal level sequence obtained in step S1, and then the corresponding tidal bore height H0 can be obtained. Repeat this process and obtain the tidal bore heights H0 corresponding to all the number of tides N0 in the first non-high-frequency tidal level sequence.

2. The method for calculating the tidal bore height of a non-high-frequency tidal level sequence according to claim 1, characterized in that, In step S1, when determining the depth turbulence g, the statistical time interval of the average water depth is set to 60 min.

3. The method for calculating the tidal bore height of a non-high-frequency tidal level sequence according to claim 1, wherein In step S2, the first high-frequency tidal level sequence needs to include 5 or more complete tidal level processes containing tidal bores.

4. The method for calculating the height of a tidal bore of a non-high-frequency tidal level sequence according to claim 1, wherein In step S6, the specific relational formula of the selected logarithmic function is: H0 = 2.93*ln(g) + 4.2, where the coefficient a = 2.93 and b = 4.

2.

5. A method for calculating the height of a tidal bore of a non-high-frequency tidal level sequence according to claim 1, characterized in that, In step S6, the specific relational formula of the selected linear function is: H0 = 6.52*g - 1.16, where the coefficient a = 6.52 and b = -1.

16.

6. The method for calculating the height of a tidal bore of a non-high-frequency tidal level sequence according to claim 1, wherein In step S6, the specific relational expression related to the selected exponential function is: H0 = 0.27e 4.0*g , where the coefficient a = 0.27 and b = 0.

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