CN101825646B - Method for measuring flow rate of thin water flow by electrolyte tracing - Google Patents

Abstract

The invention discloses a method for measuring the flow rate of a thin water flow by electrolyte tracing. The method comprises the following steps that: a saline solution is injected into an electrolyte pulse generator, and the electrolyte pulse generator injects the saline solution into a slope thin water flow; when the saline solution flows through all inducing probes, the inducing probes acquire a signal the electrical conductivity of which is changed along with time of the saline solution and transmit the signal to a data acquiring management device; the data acquiring management device transmits the signal to an operating control computer system for storage; and a data analyzing unit of the operating control computer system carries out data processing and parameter calculation according to the received signal the electrical conductivity of which is changed along with time and a formula (1) or (2) to obtain a flow rate u of a water flow, respectively generates an acquired curve graph the electrical conductivity of which is changed along with time and a simulated curve graph the electrical conductivity of which is changed along with time and records and stores the flowrate and the curve graphs. The invention greatly improves the measuring precision of the flow rate of the thin water flow, has simple operation and improves the measuring efficiency.

Description

The method of measuring flow rate of thin water flow by electrolyte tracing

Technical field

The present invention relates to the flow rate of thin water flow field of measurement, particularly a kind of method of measuring flow rate of thin water flow by electrolyte tracing.

Background technology

In the slope soil erosion process, current are the power that produces the soil erosion and make the silt migration, and the shallow flow on slopes flow velocity is the call parameter of all soil erosion process models.If the flow rate of water flow that obtains is inaccurate, be accurately even corrode the total amount prediction, the prediction of erosion process generally also is wrong.The thickness of runoff current all is the millimeter level usually, and water velocity receives the influence of multiple factors such as the gradient, length of grade, flow and underlying surface roughness, therefore, seeks a kind of method of effective measurement flow rate of water flow or emphasis and the difficult point that instrument is current research.

When there are the flow rate of water flow of obvious streamline in measurement rill or dissected valley etc.; Traditional velocimeter is because volume is too big etc. former thereby can't use; Can only adopt the current formula of open channel; Utilize parameters such as soil roughness, footpath circulation, rill width and length of grade to inquire into flow rate of water flow indirectly, but receive the influence of factors such as flow depth and silt content, result's that this method is surveyed confidence level is lower.Discharge method is simply effective for the fluid-velocity survey of regular transversal section, but in reality, is difficult to use.The thermal pulse method, the reflectorized material trace method of swimming, photoelectricity or conductivity sensor method and the electrolyte tracing method etc. that propose in the recent period, theoretical not perfect, remain further to be furtherd investigate and practical proof.

Method commonly used at present has saline solution trace method and coloring agent trace method, but receives the influence of sediment charge and fluidised form, is calculated the empirical parameter of mean flow rate by Peak Flow Rate and can not accurately confirm always.

Prior art has also proposed to utilize the method for electrolyte pulse model measurement shallow flow on slopes flow velocity, and this method adopts the solute transfer model theory, is injected into high salt concentration solution in the runoff as far as possible apace; The preset sensor at the certain position place; The change procedure of conductivity in the monitoring runoff with the one dimension convection current dispersion model match of test figure and solute transfer, calculates the parameter in the convection current disperse equation; Comprise mean flow rate, reach the purpose of measuring flow rate of water flow.This method can accurately be predicted flow rate of water flow under certain condition theoretically.Yet because the restriction of equipment, the input border is that the supposition of impulse function is difficult to realize in reality.

Summary of the invention

The technical matters that (one) will solve

The technical matters that the present invention will solve is the flow rate of thin water flow of accurately measuring on domatic, improves efficiency of measurement.

(2) technical scheme

For this reason, the invention provides a kind of method of measuring flow rate of thin water flow by electrolyte tracing, the employed device of the inventive method is placed on and produces on sheet flow domatic, and said device comprises:

The electrolyte pulse generator is used in said sheet flow, injecting salt solusion;

Several inducing probes, with a determining deviation be arranged on said domatic on, be used to gather the time dependent signal of electrical conductivity of solution, the signal that collects is sent to data acquisition unit;

Said data capture management device; Be connected with inducing probes with said electrolyte pulse generator; Be used to control said electrolyte pulse generator and begin in sheet flow, to inject solution, also be used for the conductivity signal that inducing probes is sent is sent to and control computer system;

Saidly control computer system, be connected with said data capture management device, be used for according to the time dependent signal of conductivity that receives, by formula data processing and calculation of parameter are carried out in (1) or (2), obtain flow rate of water flow;

$C_1(x,t)=\underset{0}{\overset{t}{\∫}}{C}_0\frac{x}{2(t-\mathrm{\τ})\sqrt{{\mathrm{\πD}}_H(t-\mathrm{\τ})}}\exp (-\frac{{(x-u(t-\mathrm{\τ}))}^2}{{4D}_H(t-\mathrm{\τ})})A\sin (\frac{2\mathrm{\π\τ}}{B}+D)\mathrm{d\τ}---\left(1\right)$

$C_1(x,t)=\underset{0}{\overset{t}{\∫}}{C}_0\frac{x}{2(t-\mathrm{\τ})\sqrt{{\mathrm{\πD}}_H(t-\mathrm{\τ})}}\exp (-\frac{{(x-u(t-\mathrm{\τ}))}^2}{{4D}_H(t-\mathrm{\τ})})\mathrm{Aexp}(-\frac{{(\mathrm{\τ}-D)}^2}{{2B}^2})\mathrm{d\τ}---\left(2\right)$

Wherein C representes normalized electrical conductivity of solution, C ₀Expression initial soln conductivity; C ₁Expression t electrical conductivity of solution constantly; X representes the coordinate of flowing through the length of grade direction domatic along current, and unit is m; U representes flow rate of water flow, and unit is m/s; T express time, unit are s; D _HExpression hydrodynamic dispersion coefficient, unit is m ²/ s; A, B, D are undetermined parameter.

Saidly control computer system control electrolyte pulse generator and begin in sheet flow, to inject solution.

The method of a kind of measuring flow rate of thin water flow by electrolyte tracing provided by the invention comprises:

Step 10, salt solusion is injected in the shallow flow on slopes;

Step 20, when the salt solusion flows through all inducing probes, inducing probes is gathered the time dependent signal of conductivity of salt solusion, and sends the time dependent signal of said conductivity to the data capture management device;

Step 30, data capture management device send to the signal that receives and control computer system; The data analysis unit that controls computer system is according to the time dependent signal of conductivity that receives; By formula data processing and calculation of parameter are carried out in (1) or (2), obtain flow rate of water flow u, and generate the conductivity time history plot of gathering respectively; Conductivity time history plot with simulation writes down and stores said flow velocity and curve map;

$C_1(x,t)=\underset{0}{\overset{t}{\∫}}{C}_0\frac{x}{2(t-\mathrm{\τ})\sqrt{{\mathrm{\πD}}_H(t-\mathrm{\τ})}}\exp (-\frac{{(x-u(t-\mathrm{\τ}))}^2}{{4D}_H(t-\mathrm{\τ})})A\sin (\frac{2\mathrm{\π\τ}}{B}+D)\mathrm{d\τ}---\left(1\right)$

$C_1(x,t)=\underset{0}{\overset{t}{\∫}}{C}_0\frac{x}{2(t-\mathrm{\τ})\sqrt{{\mathrm{\πD}}_H(t-\mathrm{\τ})}}\exp (-\frac{{(x-u(t-\mathrm{\τ}))}^2}{{4D}_H(t-\mathrm{\τ})})\mathrm{Aexp}(-\frac{{(\mathrm{\τ}-D)}^2}{{2B}^2})\mathrm{d\τ}---\left(2\right)$

Wherein C representes normalized electrical conductivity of solution, C ₀Expression initial soln conductivity; C ₁Expression t electrical conductivity of solution constantly; X representes the coordinate along described length of grade direction, and unit is m; U representes flow rate of water flow, and unit is m/s; T express time, unit are s; D _HExpression hydrodynamic dispersion coefficient, unit is m ²/ s, A, B, D are undetermined parameter.

Said formula (1) or (2) obtain according to following method:

For convection current disperse equation (3):

$\frac{\∂C}{\∂t}+u\frac{\∂C}{\∂x}=\frac{\∂}{\∂x}\left(D_H\frac{\∂C}{\∂x}\right)---\left(3\right)$

C representes normalized electrical conductivity of solution; X representes that unit is m along the coordinate of domatic length of grade direction; U representes flow rate of water flow, and unit is m/s; T express time, unit are s; D _HExpression hydrodynamic dispersion coefficient, unit is m ²/ s;

When upper boundary conditions is impulse function (4):

C(x，t)＝δ(t) x＝0 (4)

Downstream condition is (5):

C(x，t)＝0 x＝∞ (5)

Starting condition is (6): the initial concentration of solute is zero:

C(x，t)＝0 t＝0 (6)

The time, the analytic solution of (3) are:

$C(x,t)=C_0\frac{x}{2t\sqrt{{\mathrm{\πD}}_{H}t}}\exp (-\frac{{(x-\mathrm{ut})}^2}{{4D}_{H}t})---\left(7\right)$

Under the situation of known (7), the response of the input signal of linear system is the convolution of input signal and impulse response function, and expression formula is:

$C_1(x,t){\∫}_0^{t}C(x,t-\mathrm{\τ})f\left(\mathrm{\τ}\right)\mathrm{d\τ}---\left(8\right)$

The conductivity that to gather apart from electrolyte pulse generator inducing probes the most nearby over time signal as the boundary condition of (3); Said boundary condition is described with normal state or sine function; The expression formula of wherein separating during the sine function simulation boundary condition is (9); The expression formula of separating during normal function simulating boundary condition is (10)

In (7) and (9) substitutions (8), find the solution and obtain formula (1),

In (7) and (10) substitutions (8), find the solution and obtain formula (2).

(3) beneficial effect

The method of measuring flow rate of thin water flow by electrolyte tracing provided by the invention; Through numerical evaluation and technological the combining of modern surveying; Realized the domatic upward accurate measurement of flow rate of thin water flow has been improved measuring accuracy and efficient greatly, and simple to operate; Instrument is portable, for Model of Soil Erosion and association area research provide a good survey instrument.

Description of drawings

Fig. 1 is device embodiment one structural representation of the measuring flow rate of thin water flow by electrolyte tracing of the embodiment of the invention;

Fig. 2 is the method flow diagram of the measuring flow rate of thin water flow by electrolyte tracing of the embodiment of the invention;

Fig. 3 is device embodiment two structural representations of the measuring flow rate of thin water flow by electrolyte tracing of the embodiment of the invention;

Fig. 4 is the boundary condition conductivity time history plot of the actual measurement of the embodiment of the invention two;

Fig. 5 (a)-(i) is the matched curve figure that normal model and actual measurement solute concentration change under the different tests condition of the embodiment of the invention;

Fig. 6 (a)-(i) is the matched curve figure that sinusoidal model and actual measurement solute concentration change under the different tests condition of the embodiment of the invention;

Fig. 7 is a relatively synoptic diagram of the normal model of the embodiment of the invention and flow speed value that sinusoidal model is measured under the different tests condition.

Fig. 8 is the comparison synoptic diagram of result of calculation of measurement result and the inventive method of existing measuring method.

Wherein, 1: the electrolyte pulse generator; 2: inducing probes; 3: the data capture management device; 4: control computer system; 5: the organic glass groove; 6: water yield injection device.

Embodiment

Below in conjunction with accompanying drawing and embodiment, specific embodiments of the invention describes in further detail.Following examples are used to explain the present invention, but are not used for limiting scope of the present invention.

As shown in Figure 1, be the apparatus structure synoptic diagram of the measuring flow rate of thin water flow by electrolyte tracing of the embodiment of the invention, this device comprises: electrolyte pulse generator 1, several inducing probes 2, data capture management device 3 and control computer system 4.

Wherein electrolyte pulse generator 1 is used in shallow flow on slopes, injecting solution; This solution can be saturated KCl solution, and electrolyte pulse generator 1 can be arranged on the position that needs measurement flow rate on domatic; Several inducing probes 2 with a determining deviation be arranged on domatic in; Be used to gather the time dependent signal of electrical conductivity of solution; The signal that collects is sent to data capture management device 3; The number of inducing probes 2 can be provided with some as required, and the spacing between the inducing probes 2 can be provided with as required; Data capture management device 3 is connected with inducing probes 2 with electrolyte pulse generator 1; Be used to control electrolyte pulse generator 1 and begin in sheet flow, to inject solution, the conductivity that also is used for inducing probes 2 is sent signal over time is sent to and controls computer system 4; Control computer system 4 and be connected with data capture management device 3, be used for according to the time dependent signal of conductivity that receives, by formula data processing and calculation of parameter are carried out in (1) or (2), obtain flow rate of water flow u;

$C_1(x,t)=\underset{0}{\overset{t}{\∫}}{C}_0\frac{x}{2(t-\mathrm{\τ})\sqrt{{\mathrm{\πD}}_H(t-\mathrm{\τ})}}\exp (-\frac{{(x-u(t-\mathrm{\τ}))}^2}{{4D}_H(t-\mathrm{\τ})})A\sin (\frac{2\mathrm{\π\τ}}{B}+D)\mathrm{d\τ}---\left(1\right)$

$C_1(x,t)=\underset{0}{\overset{t}{\∫}}{C}_0\frac{x}{2(t-\mathrm{\τ})\sqrt{{\mathrm{\πD}}_H(t-\mathrm{\τ})}}\exp (-\frac{{(x-u(t-\mathrm{\τ}))}^2}{{4D}_H(t-\mathrm{\τ})})\mathrm{Aexp}(-\frac{{(\mathrm{\τ}-D)}^2}{{2B}^2})\mathrm{d\τ}---\left(2\right);$

Wherein C representes normalized electrical conductivity of solution, C ₀Expression initial soln conductivity; C ₁Expression t electrical conductivity of solution constantly; X representes that unit is m along the coordinate of domatic length of grade direction; U representes flow rate of water flow, and unit is m/s; T express time, unit are s; D _HExpression hydrodynamic dispersion coefficient, unit is m ²/ s; A, B, D are undetermined parameter.

The device of the measuring flow rate of thin water flow by electrolyte tracing that present embodiment provides is used to measure the flow velocity of shallow flow on slopes.Wherein, controling computer system also can control the electrolyte pulse generator and begin in sheet flow, to inject solution.

Wherein the derivation of formula (1) and (2) is following:

Salt solusion is injected in the rainwash, will with current generation convection current dispersion, the travel motion of salt solusion in water is a very complicated process, influenced by several factors, like flow rate of water flow, water flow mud-sand content, water quality etc.In order to quantize this process effectively, propose following 3 fundamental assumptions in the prior art and set up measurement model:

1) current are one-dimensional stable stream, and solute transfer also is an one dimension;

2) flow velocity in given measuring distance can be thought mean value, is constant;

3) it is very short initially to inject time of salt solusion, can suppose the coincidence impulse function.

According to top 3 hypothesis and do not consider rainfall and infiltrate when influencing that the convection current disperse equation of solute in the one-dimensional stable current is:

$\frac{\∂C}{\∂t}+u\frac{\∂C}{\∂x}=\frac{\∂}{\∂x}\left(D_H\frac{\∂C}{\∂x}\right)---\left(3\right)$

In the formula, C representes normalized electrical conductivity of solution; X representes that unit is m along the coordinate of domatic length of grade direction; U representes flow rate of water flow, and unit is m/s; T express time, unit are s; D _HExpression hydrodynamic dispersion coefficient, unit is m ²/ s.

According to model hypothesis, upper boundary conditions is impulse function δ (t), and expression formula is:

C(x，t)＝δ(t) x＝0 ?(4)

Suppose the tank endless, so downstream condition is Dirichlet first kind border, expression formula is:

C(x，t)＝0 x＝∞ (5)

The initial concentration of solute is zero in the runoff, so starting condition is:

C(x，t)＝0 t＝0 (6)

Simultaneous partial differential equations (3), boundary condition (4), (5) and starting condition (6) utilize Laplace transform (Laplace " s transformation) to try to achieve the analytic solution of model, as follows:

$C(x,t)=C_0\frac{x}{2t\sqrt{{\mathrm{\πD}}_{H}t}}\exp (-\frac{{(x-\mathrm{ut})}^2}{{4D}_{H}t})---\left(7\right)$

Formula (7) is the analytic solution of solute convection disperse equation when on top boundary's condition is unit impulse function.C wherein ₀Expression solution initial conductivity, C ₀, u and D _HBe undetermined parameter.

The embodiment of the invention is improved the upper boundary conditions impulse function of above-mentioned measurement model of the prior art; On the approach of flow of solution warp inducing probes is set on domatic; The conductivity of gathering solution by inducing probes is signal over time; According to the actual conductivity data that records rule over time, adopt normal function and sine function to be similar to the match boundary condition.After boundary condition is known, utilize the Duhamel integration, the convolutional calculation that the true input of model is promptly imported by the impulse response and the actual boundary of this system.The design experiment device is collected the variation of conductivity on time and space, with the model solution match under the actual boundary condition, utilizes least square method to calculate average flow rate of water flow.

Wherein the expression formula of sine function simulation boundary condition is:

In the formula, parameter A, B, D can pass through formula (8) and calculate apart from the conductivity variations data fitting of the nearest inducing probes actual measurement of solution decanting point.

For a linear system, the response function of effect under the known unit pulse signal, promptly under the situation of equation (7), the response of any input signal is the convolution of input signal and impulse response function, formula is following:

$C_1(x,t)={\∫}_0^{t}C(x,t-\mathrm{\τ})f\left(\mathrm{\τ}\right)\mathrm{d\τ}---\left(9\right)$

Formula (7) and (8) are updated in the formula (9), obtain when actual boundary is input as the Sine distribution function, corresponding separates as follows:

$C_1(x,t)=\underset{0}{\overset{t}{\∫}}{C}_0\frac{x}{2(t-\mathrm{\τ})\sqrt{{\mathrm{\πD}}_H(t-\mathrm{\τ})}}\exp (-\frac{{(x-u(t-\mathrm{\τ}))}^2}{{4D}_H(t-\mathrm{\τ})})A\sin (\frac{2\mathrm{\π\τ}}{B}+D)\mathrm{d\τ}---\left(1\right)$

In like manner: the expression formula of normal function simulating boundary condition is:

In formula (7) and (10) substitution formula (9), obtain when actual boundary is input as normal distyribution function, corresponding separates as follows:

$C_1(x,t)=\underset{0}{\overset{t}{\∫}}{C}_0\frac{x}{2(t-\mathrm{\τ})\sqrt{{\mathrm{\πD}}_H(t-\mathrm{\τ})}}\exp (-\frac{{(x-u(t-\mathrm{\τ}))}^2}{{4D}_H(t-\mathrm{\τ})})\mathrm{Aexp}(-\frac{{(\mathrm{\τ}-D)}^2}{{2B}^2})\mathrm{d\τ}---\left(2\right)$

As shown in Figure 2, be the method flow diagram of the measuring flow rate of thin water flow by electrolyte tracing of inventive embodiments, this method is used the device of the foregoing description, and this method comprises the steps:

Step 10, saturated salt solution is injected in the shallow flow on slopes;

This step is used the electrolyte pulse generator, and saturated salt solution is injected in the electrolyte pulse generator, and the electrolyte pulse generator is injected into saturated salt solution in the sheet flow according to the control indication of data capture management device;

Step 20, after the saturated salt solution flows through all inducing probes, inducing probes is gathered the time dependent signal of conductivity of saturated salt solution, and sends the time dependent signal of this conductivity;

In this step, inducing probes is sent to the data capture management device with the signal that collects, and the data capture management device is sent to this signal and controls computer system;

The time dependent signal of conductivity that step 30, basis receive; By formula data processing and calculation of parameter are carried out in (1) or (2); Try to achieve flow rate of water flow u; And generate the conductivity time history plot of gathering respectively, and with the conductivity time history plot of simulation, record and storage flow velocity and curve map.

The data analysis computing system that controls in the computer system utilizes formula (1) or (2) to calculate flow rate of thin water flow.

As shown in Figure 3, be device embodiment two structural representations of the measuring flow rate of thin water flow by electrolyte tracing of the embodiment of the invention; Present embodiment is simulated the measuring process to flow rate of thin water flow on domatic in testing laboratory, as the accuracy and the efficient of example checking this method, present embodiment also is provided with organic glass groove 5 and water yield injection device 6 for this reason.

Organic glass groove 5 long 4m wherein, high 50cm, wide 15cm is certain slope and places, and such as can being 4 ° with ground, or 8 °, or 12 ° of angles wait and place, and are used for that is virtually reality like reality domatic.In the more stable position of organic glass groove 5 top current the solution decanting point is set, rule of thumb, current reach stable generally speaking apart from the 1m place, top of organic glass groove 1, therefore can the solution decanting point be set at this point; Water yield injection device 6 is used for injecting clear water to organic glass groove 5, forms the runoff of certain flow, is used to simulate domatic sheet flow; Electrolyte pulse generator 1 is placed near the solution decanting point, is used for saturated potassium chloride (salt) solution is injected organic glass guide channel 5; Inducing probes 2 is arranged on the organic glass groove 5 with certain spacing, is used to gather the time dependent signal of conductivity of salt solusion, and the signal that collects is sent to data capture management device 3; Can be arranged on apart from solution decanting point 5cm, 30cm, 60cm, 90cm, 120cm and 150cm place such as inducing probes 2.Data capture management device 3 is connected with inducing probes 2; Be used to receive the signal that inducing probes 2 is gathered; The signal that receives is sent to controls computer system 4, control computer system 4, generate the conductivity time history plot of actual measurement according to the conductivity signal that receives; And the time dependent function relation figure of conductivity of simulation, and by formula flow rate of water flow u is tried to achieve through computer simulation in (1) or (2).

As shown in Figure 4, be the boundary condition conductivity time history plot of the actual measurement of the embodiment of the invention two.

According to the data that change between the concentration of salt solution data changes with time that records under the different tests condition; According to formula (1) computation model parameter; Obtain matched curve figure that normal model under the different tests condition and actual measurement solute concentration change shown in Fig. 5 (a)-(i), as can be seen from the figure, the solution concentration and the measured data match of normal model prediction reach unanimity; Can catch the trend of peak value and density loss preferably, confirm that coefficient is basically all greater than 0.9.The mean flow rate that the different measuring distance calculation obtains under the different tests condition is as shown in table 1.Can be found out that by data in the table 1 mean flow rate of model prediction increases along with the increase of the gradient and flow gradually, this is true to life.In addition, the mean flow velocity value difference of different measuring position prediction is very little, and this also is consistent with the prerequisite of Model Calculation.Therefore, the theory and the parametric solution rationality of procedure of normal model are described.

Table 1: the mean flow velocity value that normal model and sinusoidal model calculate (m/s)

The data that change between the concentration of salt solution data changes with time that records according to the diverse location place; According to formula (2) computation model parameter; Obtain matched curve figure that sinusoidal model under the different tests condition and actual measurement solute concentration change shown in Fig. 6 (a)-(i); Visible by Fig. 6 (a)-(i), under different gradient and flow condition, sinusoidal model is very consistent with the match of measured data.Along with the increase of the gradient and flow, the single electrolyte significantly shortened through the time of inducing probes.Confirm that coefficient is almost all greater than 0.9.

Under the different tests condition, sinusoidal model is as shown in table 1 at the current mean flow velocity value of each place, measuring position prediction.Changing Pattern between the flow speed value that the test figure of utilizing the diverse location place to measure calculates is not clearly, and the result of T check also shows that flow velocity does not have significant difference between different measuring positions.This result shows that insulated stream is stable state basically, and this hypothesis with model is consistent.The slope flow flow velocity is along with the increase of flow and organic glass trough slope is the trend of increase, and flow is more remarkable to the influence of flow velocity than the gradient to the influence of flow velocity, and this conclusion is rational.Therefore, show that it is rational utilizing the sine function simulation border to calculate the shallow flow on slopes flow velocity through analysis.

The rationality that predicts the outcome comparative analysis flow velocity prediction through normal model and sinusoidal model below.As shown in Figure 7, the flow speed value of under the different tests condition, measuring for normal model and sinusoidal model is synoptic diagram relatively, and is visible, and all data points nearly all drop near 1: 1 the straight line, explain that two models do not have significant difference when predicted velocity.

Therefore; Normal distyribution function and sine function all can be simulated the boundary condition of actual acquisition preferably; The normal model of setting up as boundary condition and sinusoidal model be the measured data of match position well, and predicts that the flow rate of water flow value has rationality with the variation of the flow and the gradient.Average flow rate of water flow through two model predictions does not have significant difference, has further proved the rationality and the feasibility of model.

Below the discharge method of measurement flow rate in normal model, sinusoidal model and the prior art of the embodiment of the invention and the measurement result of floating thing method are compared the accuracy of checking normal model and sinusoidal model predicted velocity.As shown in Figure 8, be the comparison synoptic diagram of the result of calculation of the measurement result of existing measuring method and the inventive method, and utilize linear regression fit.The result shows: the flow speed value that discharge method records is normal model and sinusoidal model result of calculation 0.789 times, and deterministic coefficient is 0.854.The flow ratio juris is to utilize monitoring water flow and depth of water calculation flow rate; Wherein flow is measured with integral bucket; The depth of water is with water level instrumentation amount; The flow velocity precision that discharge method calculates depends primarily on the measuring accuracy of the depth of water, because the precision of water level gauge is 1/10mm, this just means that discharge method measurement flow rate of thin water flow also has 10% relative error.Analyze in view of the above, flow speed value that discharge method is measured and the difference between normal model and the sinusoidal model result of calculation can be explained, can reflect the rationality of The model calculation.The flow speed value that the floating thing method is measured is 1.013 times of method result of calculation of the present invention, and deterministic coefficient is 0.801, and the flow velocity difference that records with the present invention is very little, and this result further illustrates the accuracy of normal model and sinusoidal model result of calculation.

The method of measuring flow rate of thin water flow by electrolyte tracing provided by the invention; Through with the conductivity of solution over time signal through combining of numerical evaluation and modern surveying technology, realized in the short distance measurement as the boundary condition of convection current disperse equation to flow rate of thin water flow; Improved measuring accuracy greatly; And simple to operate, instrument is portable, for Model of Soil Erosion and association area research provide a good survey instrument.

The above only is a preferred implementation of the present invention; Should be pointed out that for those skilled in the art, under the prerequisite that does not break away from know-why of the present invention; Can also make some improvement and modification, these improve and modification also should be regarded as protection scope of the present invention.

Claims (1)

1. the method for a measuring flow rate of thin water flow by electrolyte tracing is characterized in that, comprises the steps:

Step 10, salt solusion is injected in the shallow flow on slopes;

Step 20, when the salt solusion flows through all inducing probes, inducing probes is gathered the time dependent signal of conductivity of salt solusion, and sends the time dependent signal of said conductivity to the data capture management device;

Step 30, data capture management device send to the signal that receives and control computer system; The data analysis unit that controls computer system is according to the time dependent signal of conductivity that receives; By formula data processing and calculation of parameter are carried out in (1) or (2), obtain flow rate of water flow u, and generate the conductivity time history plot of gathering respectively; Conductivity time history plot with simulation writes down and stores said flow velocity and curve map;

$C_1(x,t)=\underset{0}{\overset{t}{\∫}}{C}_0\frac{x}{2(t-\mathrm{\τ})\sqrt{{\mathrm{\πD}}_H(t-\mathrm{\τ})}}\exp (-\frac{{(x-u(t-\mathrm{\τ}))}^2}{{4D}_H(t-\mathrm{\τ})})A\sin (\frac{2\mathrm{\π\τ}}{B}+D)\mathrm{d\τ}---\left(1\right)$

$C_1(x,t)=\underset{0}{\overset{t}{\∫}}{C}_0\frac{x}{2(t-\mathrm{\τ})\sqrt{{\mathrm{\πD}}_H(t-\mathrm{\τ})}}\exp (-\frac{{(x-u(t-\mathrm{\τ}))}^2}{{4D}_H(t-\mathrm{\τ})})\mathrm{Aexp}(-\frac{{(\mathrm{\τ}-D)}^2}{{2B}^2})\mathrm{d\τ}---\left(2\right)$

Wherein C representes normalized electrical conductivity of solution, C ₀Expression initial soln conductivity; C ₁Expression t electrical conductivity of solution constantly; X representes the coordinate of flowing through the length of grade direction domatic along current, and unit is m; U representes flow rate of water flow, and unit is m/s; T express time, unit are s; D _HExpression hydrodynamic dispersion coefficient, unit is m ²/ s, A, B, D are undetermined parameter;

Said formula (1) or (2) obtain according to following method:

For convection current disperse equation (3):

$\frac{\∂C}{\∂t}+u\frac{\∂C}{\∂x}=\frac{\∂}{\∂x}\left(D_H\frac{\∂C}{\∂x}\right)---\left(3\right)$

C representes normalized electrical conductivity of solution; X representes that unit is m along the coordinate of domatic length of grade direction; U representes flow rate of water flow, and unit is m/s; T express time, unit are s; D _HExpression hydrodynamic dispersion coefficient, unit is m ²/ s;

When upper boundary conditions is impulse function (4):

C (0, t)=δ (t) C (x, t)=δ (t) x=0 (4) downstream condition is (5):

C(x，t)＝0 x＝∞ (5)

Starting condition is (6): the initial concentration of solute is zero:

C(x，t)＝0 t＝0 (6)

The time, the analytic solution of (3) are:

$C(x,t)=C_0\frac{x}{2t\sqrt{{\mathrm{\πD}}_{H}t}}\exp (-\frac{{(x-\mathrm{ut})}^2}{{4D}_{H}t})---\left(7\right)$

Under the situation of known (7), the response of the input signal of linear system is the convolution of input signal and impulse response function, and expression formula is:

$C_1(x,t)={\∫}_0^{t}C(x,t-\mathrm{\τ})f\left(\mathrm{\τ}\right)\mathrm{d\τ}---\left(8\right)$

The conductivity that to gather apart from electrolyte pulse generator inducing probes the most nearby over time signal as the boundary condition of (3); Said boundary condition is described with normal state or sine function; The expression formula of wherein separating during the sine function simulation boundary condition is (9); The expression formula of separating during normal function simulating boundary condition is (10)

In (7) and (9) substitutions (8), find the solution and obtain formula (1),

In (7) and (10) substitutions (8), find the solution and obtain formula (2).

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