CN106595777A - Calculation method for detecting flow of section of river in non-contact manner - Google Patents

Abstract

The invention relates to a calculation method for detecting the flow of the section of a river in a non-contact manner. The method includes the following steps that: step 1, a radar is adopted to detect river surface flow data; step 2, open channel flow cross section flow rate distribution is calculated; step 3, a relationship between a surface flow rate and a water depth is determined; step 4, a relationship between the surface flow rate and the average flow rate of the section is determined; and step 5, the total flow of the section is calculated. According to the calculation method of the invention, a radar remote sensing non-contact measurement method is adopted, so that good maneuverability, flexibility and real-time performance can be realized, and highest detection efficiency can be achieved with smallest measurement cost, a widest detection range can be realized, and measurement can be performed in a non-water-contact manner; and therefore, the calculation method is competent for hydrological surface information measurement under complex geological conditions and external adverse weather conditions.

Description

A kind of computational methods of contactless detection cross section of river flow

Technical field

The present invention relates to flow monitoring technical field, more particularly to a kind of meter of contactless detection cross section of river flow Calculation method.

Background technology

The method that prior art is measured for water body, the mode obtained according to data can be divided into direct measurement and contact Measurement.Direct measurement and contact type measurement are mainly taken and measuring instrument are put in measurement target water body so as to obtain water body phase The method for closing hydrology parameter information, is such as all the side of direct measurement and contact type measurement using current meter, current meter, buoy etc. Method.But when external environment condition is severe, such as under the conditions of typhoon, flood etc., direct measurement and contact type measurement are difficult to carry out, and cannot do To daytime measurement, and also will be through proving at this repeatedly water body environment if appropriate for being surveyed in the selection of measurement point Amount, measurement range are little.

The content of the invention

In order to overcome the deficiencies in the prior art, the technical problem to be solved is to provide one kind can be disconnected to river Surface current amount carries out the wide method of daytime measurement and measurement range.

To solve above-mentioned technical problem, a kind of calculating side of contactless detection cross section of river flow provided by the present invention Method, comprises the steps：

Step 1 uses radar detection river surface flow data；

Step 2 calculates the distribution of channel flow cross-sectional flow；

According to hydromechanical principle, the governing equation group of two-dimentional channel flow under constant stream mode is obtained：

Still cannot get the distribution of cross-sectional flow by above-mentioned governing equation, will obtain flow velocity vertical characteristics need to be using some partly The public affairs of experience

Formula method.According to the semi-empirical approach of the mixing length theory l=κ z ' of Prandtl, and shearing stress τ of inner region_zx It is basic to keep constant value and be equal to wall shear stress τ₀Obtain equation below：

Variables separation, to obtaining after differential equation integration：

Wherein,For drag velocity, κ is toll bar general constant, and integral constant C is determined by experimental data.z₀ For bed surface rough features length, it is riverbed roughness k_sFunction, represent flow velocity be at zero with a distance from riverbed bottom, that is, The original position of virtual bed bottom z', typically takesAnd riverbed roughness k_sIt is then the parameter of tolerance bed surface degree of roughness；

In outskirt, because τ_zx≠τ₀, logarithmic parabola can not possibly be compound with actual, it is necessary to introduces a function and is corrected, The function depends on function h, while also depending on zero dimension barometric gradientHere Coles wake flow function pairs pair are introduced Number formula is modified, and obtains outskirt empirical equation：

Wherein U_cFor the Peak Flow Rate in section,For wake flow function, it is defined as：And Π is wake flow Parameter, depending on longitudinal gradient force：

For the current of balance, wake flow parameter must keep constant value, thus β is a balance parameters.(2 Π/k) generation Deviate the part of logarithmic parabola at table (z'/δ)=1, depth of water δ≤h is Peak Flow Rate U to be measured in active cross-section_cThe depth at place, such as Fruit Peak Flow Rate occurs in the water surface, then δ ≡ h.

Step 3 determines the relation of surface velocity and the depth of water；

Formula of the flow velocity along water depth distribution is determined, the numerical value of the depth of water can be further calculated.According to flow velocity experience point Cloth formula, surface velocityThe power form related to depth of water h can be expressed as：

Wherein, z₀For bed surface rough features length, represent that flow velocity is that is, the virtual bed at 0 with a distance from riverbed bottom The position at bottom.And coefficient a and m are the parameter relevant with bed configuration and stream condition；

Bring drag velocity expression formula into above-mentioned formula and obtain depth of water expression formula：

k_sIt is riverbed roughness, S_fFor bed sloped, g is acceleration of gravity, in natural rivers and creeks, when object is the big depth of water During small particle riverbed rivers and creeks, the suggestion of Engelund is：M=1/8, A=9.45.

Step 4 determines the relation of surface velocity and mean velocity in section；

Obtaining flow velocity and obtaining after water depth distribution, further the mean flow rate of cross section of river；

1. according to conventional empirical equation, mean velocity in section U is determined using following approximation relation：

The numerical value of above parameter represents the depth of water of given position, the behalf water surface；

In natural rivers and creeks, in the case where horizontal bed surface Latitudinal section is uneven, empirically method is calculated and is easily caused Calculation error, according to velocity distribution formulas, asks for mean velocity in section in the way of integrating；

2. according to cross-sectional flow formula, integration is calculated respectively by inner region and outskirt to cross-sectional flow, with 0.2h as interior outskirt Separation, obtains outskirt mean flow rate U₀, inner region mean flow rate U_i, then section flat average rate U can be by formula

U=0.8U₀+0.2U₁Represent, interior outskirt mean flow rate expression formula is brought into and is obtained：

Above formula is obtained into the ratio of mean flow rate and surface velocity divided by velocity distribution formulas：

3., in the case of with power velocity distribution formulas, the deep integral mean of water intaking obtains section depth of water mean flow rate For：

By Velocity Formula divided by power velocity distribution formulas, the ratio of section depth of water mean flow rate and surface velocity is obtained It is worth and is：

Step 5 calculates section total flow；

Using average cross method, the total flow for obtaining a distance element section is：

Wherein, B is river width, and n is segments, B_iTo be segmented river width, U_iFor the mean flow rate of this distance element section, h_iFor The depth of water, wherein U₀、U_n、h₀And h_nFor the mean flow rate and the depth of water of border segment, 0 value in calculating, can be considered as.

Beneficial effects of the present invention

(1) if the interval between section is less, that is, radar range unit interval it is less when, can be abundant

Show the horizontal change conditions for flowing to situation and riverbed in rivers and creeks.

(2) using radar detection remote sensing, spatially while measurement flow rate and depth profile, can grasp rapidly riverbed change The situation of dynamic and velocity flow profile, for the control of riverbed discharge and the raising of certainty of measurement have significantly help.

(3) can be due to cross section of river, transversely detecting location is different, and the depth of water for causing is different with velocity flow profile examines Including considering, improve the accuracy of flow rate calculation, while overcoming the limitation of conventional remote sensing technology measurement, reach with contactless The purpose of the accurate calculated flow rate of means.

The method of radar remote sensing non-contact measurement has good mobility, motility, real-time, with minimum measurement Cost reaches the detection efficient of maximum, covers most wide investigative range, not contact the advantage of water body measurement, can be competent at complexity Hydrology surface information measurement under geological conditions and outside adverse weather condition.

Description of the drawings

Fig. 1 is radar detection top view；

Fig. 2 is the flow chart of cross section of river flow rate calculation.

Specific embodiment

The invention will be further described below in conjunction with the accompanying drawings：

Fig. 1 is radar detection top view.In actual tests operation, according to the situation of change of river level, and test The characteristics of water phase time period, to select and place is set up as radar at one.It can be seen from figure 1 that radar #11 is irradiated towards on river Trip, flowing water are all directed towards radar motion.

Fig. 2 is the flow chart of the cross section of river flow rate calculation using the present invention.With non-contacting technique study section Hydrologic parameter, main data are according to the surface velocity for being exactly section at this.Based on detection target, present invention assumes that detection section Current be steady flow.Steady flow is generally dependent on x, y, z these three variables, is exactly so-called three-dimensional current.If a river The width of groove is very big, and for the depth of water, then this current is considered as two dimension.For the calculating of cross section of river flow, High-frequency ground wave radar searching surface stream can be used, according to the method that surface stream further sets up flow rate calculation pattern, with river table The data of surface current obtain section upper table surface current as foundationDistribution, according to surface velocity and the depth of water and mean velocity in section Relation, calculates the depth of water and mean velocity in section, section flow is obtained after integration.

For the estimation of the section depth of water and mean flow rate：It is Peak Flow Rate that cross-section average depth is calculated based on surface velocity This premise.The present invention adopts power law formula in the calculating to the depth of water, and adopts parameter m=1/8, and A=9.45 is counting Calculate depth of water result.After obtaining section water depth distribution, mean flow rate calculating is carried out to a certain distance element section that target section is chosen.

For the selection of calculating parameter：The present invention utilizes measurement surface flow relocity calculation mean flow rate and the depth of water, and then tries to achieve The method of section flow, the parameter of Main Basiss is energy gradient and riverbed roughness length.According to energy gradient is actually obtained For：S_e=S_w+F_r ²(S_f-S_w), S_fFor bed sloped, S_wFor water surface gradient.F_rFor Floyd's algorithm.Current invention assumes that target section Section current are open-channel constant uniform flow, and according to current property and characteristic of river course, water surface gradient can be near with stream gradient Patibhaga-nimitta etc., then energy gradient determined by river water surface gradient.I.e.：S_e=S_w=S_f.Believed according to the hydrology in existing target river Breath, show that the order of magnitude of bed roughness refers to span.

For the acquisition of surface velocity：The present invention utilizes the radar exploration technique gathered data, how general according to the distance for obtaining The practical situation and current direction of spectrogram are strangled, that analyzes the right and left single order peak manifests degree, it is ensured that manifesting obvious one Side single order peak substantially exist in the range of will not be with opposite side single order peak in the case that after zero-frequency is crossed, residing region is Chong Die, table Surface current speed extracts the flow rate information that can be provided only with the single order peak of side.

For the calculating of section flow：First have to model estimation be carried out to calculating section, the stream shape of section is carried out Approximate evaluation.The present invention regards section shape as conventional trapezoidal, is approximately considered current with river surface center as line of symmetry, section Mean flow rate is symmetrical.Relevant parameter formula is as follows：

Section：A=(b+mh) h width：The B=b+2mh depth of waters：

Then, on section, river width B is divided into some sections. for each segment B_i, it is distributed according to radar detection surface low Data, obtain the average surface flow velocity of each segmentAnd then it is light-gauge average to be calculated this according to formula Flow velocity U_iWith depth of water h_i, using average cross method, obtain total flow Q of this distance element section：

Wherein, B is river width, and n is segments, B_iTo be segmented river width, wherein U₀、U_n、h₀And h_nFor side

The mean flow rate and the depth of water of area under a person's administration, can be considered as 0 value in calculating.

Claims (5)

1. a kind of computational methods of contactless detection cross section of river flow, the method comprises the steps：

Step 1 uses radar detection river surface flow data；

Step 2 calculates the distribution of channel flow cross-sectional flow；

Step 3 determines the relation of surface velocity and the depth of water；

Step 4 determines the relation of surface velocity and mean velocity in section；

Step 5 calculates section total flow；

It is characterized in that：Described detection river surface flow data is detected with radar electromagnetic wave.

2. it is according to claim 1 it is contactless detection cross section of river flow computational methods, it is characterised in that：Described The distribution of channel flow cross-sectional flow is calculated, it is specific as follows：

According to hydromechanical principle, the governing equation group of two-dimentional channel flow under constant stream mode is obtained：

$\stackrel{\‾}{u}\frac{\∂\stackrel{\‾}{u}}{\∂x}+\stackrel{\‾}{w}\frac{\∂\stackrel{\‾}{u}}{\∂z}=-g\left(\frac{\∂h}{\∂x}+\frac{\∂z_b}{\∂x}\right)+\frac{1}{\mathrm{\ρ}}\frac{\∂{\mathrm{\τ}}_{zx}}{\∂z}$

$\stackrel{\‾}{P}=\mathrm{\ρ}g(h-z^{\′})-\mathrm{\ρ}{\stackrel{\‾}{w}}^2$

$\frac{\∂\stackrel{\‾}{u}}{\∂x}+\frac{\∂\stackrel{\‾}{w}}{\∂z}=0$

Still cannot get the distribution of cross-sectional flow by above-mentioned governing equation, flow velocity vertical characteristics will be obtained and need to adopt some semiempiricals Formula method.According to the semi-empirical approach of the mixing length theory l=κ z ' of Prandtl, and shearing stress τ of inner region_zxSubstantially Keep constant value and be equal to wall shear stress τ₀Obtain equation below：

${\mathrm{\τ}}_{zx}\≡{\mathrm{\τ}}_0={\mathrm{\ρ\κ}}^2{z}^{\′2}{\left(\frac{d\stackrel{\‾}{u}}{dz}\right)}^2$

Variables separation, to obtaining after differential equation integration：

$\frac{\stackrel{\‾}{u}}{u^{*}}=\frac{1}{k}\ln z^{\′}+C$

Wherein,For drag velocity, κ is toll bar general constant, and integral constant C is determined by experimental data.z₀For bed surface Rough features length, is riverbed roughness k_sFunction, represent that flow velocity is that is, the virtual bed at zero with a distance from riverbed bottom The original position of bottom z', typically takesAnd riverbed roughness k_sIt is then the parameter of tolerance bed surface degree of roughness；

In outskirt, because τ_zx≠τ₀, logarithmic parabola can not possibly be compound with actual, it is necessary to introduces a function and is corrected, the letter Number depends on function h, while also depending on zero dimension barometric gradientHere introduce Coles wake flow function pairs logarithm public Formula is modified, and obtains outskirt empirical equation：

$\frac{U_c-u}{u^{*}}=\frac{1}{k}\ln \left(\frac{\mathrm{\δ}}{z^{\′}}\right)+\frac{\Π}{k}(2-\stackrel{\‾}{w})$

Wherein U_cFor the Peak Flow Rate in section,For wake flow function, it is defined as：And Π is wake flow parameter, Depending on longitudinal gradient force：

$\Π=f\left(\mathrm{\β}\right),\mathrm{\β}=\frac{h}{{\mathrm{\τ}}_0}\frac{\∂\stackrel{\‾}{p^{*}}}{\∂x}$

For the current of balance, wake flow parameter must keep constant value, thus β is a balance parameters.(2 Π/k) are represented Deviate the part of logarithmic parabola at (z'/δ)=1, depth of water δ≤h is Peak Flow Rate U to be measured in active cross-section_cThe depth at place, if Peak Flow Rate occurs in the water surface, then δ ≡ h.

3. it is according to claim 1 it is contactless detection cross section of river flow computational methods, it is characterised in that：Described Determine the relation of surface velocity and the depth of water, it is specific as follows：

Formula of the flow velocity along water depth distribution is determined, the numerical value of the depth of water can be further calculated.It is public according to the distribution of flow velocity experience Formula, surface velocityThe power form related to depth of water h can be expressed as：

$\frac{\stackrel{\‾}{u_s}}{u^{*}}=a{\left(\frac{h}{z_0}\right)}^m$

Wherein, z₀For bed surface rough features length, represent that flow velocity is that is, the position at virtual bed bottom at 0 with a distance from riverbed bottom Put.And coefficient a and m are the parameter relevant with bed configuration and stream condition；

Bring drag velocity expression formula into above-mentioned formula and obtain depth of water expression formula：

$h={\left(\frac{{\stackrel{\‾}{u}}_s{k_s}^m}{A(1+m)\sqrt{{\mathrm{gS}}_f}}\right)}^{\frac{2}{2m+1}}$

k_sIt is riverbed roughness, S_fFor bed sloped, g is acceleration of gravity, in natural rivers and creeks, when object is big depth of water granule During footpath riverbed rivers and creeks, the suggestion of Engelund is：M=1/8, A=9.45.

4. it is according to claim 1 it is contactless detection cross section of river flow computational methods, it is characterised in that：Described Determine the relation of surface velocity and mean velocity in section, it is specific as follows：

Obtaining flow velocity and obtaining after water depth distribution, further the mean flow rate of cross section of river；

1. according to conventional empirical equation, mean velocity in section U is determined using following approximation relation：

$U\≅(0.8~0.9)\stackrel{\‾}{U_S}$

$U\≅0.5(\stackrel{\‾}{u_{0.2}}+\stackrel{\‾}{u_{0.8}})$

$U\≅\stackrel{\‾}{u_{0.4}}$

The numerical value of above parameter represents the depth of water of given position, the behalf water surface；

In natural rivers and creeks, in the case where horizontal bed surface Latitudinal section is uneven, empirically method is calculated and easily causes calculating Error, according to velocity distribution formulas, asks for mean velocity in section in the way of integrating；

2. according to cross-sectional flow formula, integration is calculated respectively by inner region and outskirt to cross-sectional flow, with 0.2h as inside and outside differentiation circle Point, obtains outskirt mean flow rate U₀, inner region mean flow rate U_i, then section flat average rate U can be by formula U=0.8U₀+0.2U₁Table Show, interior outskirt mean flow rate expression formula is brought into and is obtained：

$\frac{0.8\stackrel{\‾}{u_s}-U}{u^{*}}=\frac{1}{\mathrm{\κ}}\[\left(0.2+\frac{k_s}{30h}\right)In\left(1+\frac{6h}{k_s}\right)\]+0.612\Π+0.678$

Above formula is obtained into the ratio of mean flow rate and surface velocity divided by velocity distribution formulas：

$\frac{U}{u_s}=0.8-\left\{\[-\left(0.2+\frac{k_s}{30h}\right)\ln \left(1+\frac{6h}{k_s}\right)+0.612\Π+0.678\]/\ln \frac{30h}{k_s}+1.81\Π\right\}$

3. in the case of with power velocity distribution formulas, the deep integral mean of water intaking, obtaining section depth of water mean flow rate is：

$\frac{U}{u^{*}}=\frac{a}{(1+m)}\[\frac{z_0}{h}{\left(\frac{h+z_0}{z_0}\right)}^m-\frac{z_0}{h}\]$

By Velocity Formula divided by power velocity distribution formulas, the ratio of section depth of water mean flow rate and surface velocity is obtained For：

$\frac{U}{\stackrel{\‾}{u_s}}=\frac{1}{1+m}{\left(\frac{k_s}{30h}\right)}^{m+1}\[{\left(\frac{30h}{k_s}+1\right)}^{m+1}-1\]$

5. it is according to claim 1 it is contactless detection cross section of river flow computational methods, it is characterised in that：Described Section total flow is calculated, it is specific as follows：

Using average cross method, the total flow for obtaining a distance element section is：

$Q=\underset{0}{\overset{B}{\∫}}\left(U\·h\right)dx\≈\underset{i=0}{\overset{n}{\Σ}}\[\frac{1}{4}(U_i+U_{i+1})\·(h_i+h_{i+1})\·B_i\]$

Wherein, B is river width, and n is segments, B_iTo be segmented river width, U_iFor the mean flow rate of this distance element section, h_iFor the depth of water, Wherein U₀、U_n、h₀And h_nFor the mean flow rate and the depth of water of border segment, 0 value in calculating, can be considered as.