CN102538912B - Method for analyzing additive errors of flow field of ultrasonic flowmeter - Google Patents

Abstract

The invention relates to a method for analyzing additive errors of a flow field of an ultrasonic flowmeter, which is characterized in that fluid dynamic numerical simulation is performed to liquid flow of a flowmeter in a pipeline within a certain range of upstream and downstream. Splash flow velocity information of the flow field in the pipeline is acquired by utilizing the fluid dynamic numerical simulation, the flow velocity is interpolated onto each sound channel of the flowmeter, sound channel speed of each sound channel is calculated according to the fundamental principle of the flowmeter, and weighted summation is further performed to obtain an indicating flow. Surface integral is performed to main flow velocity of flowmeter cross section flow field splashes, or weighted summation is performed to sound channel speed main flow contributions of a plurality of sound channels collected in a cross section flow field so as to obtain a standard flow of the flow field. Difference of the indicating flow and the standard flow is analyzed to obtain the additive errors of the flow field. By means of the method, quick and accurate evaluation of the additive errors of the flow field is achieved, and the fact that the flow measurement problem is solved by utilizing a numerical method has good reference significance.

Description

Method for analyzing additive errors of flow field of ultrasonic flowmeter

Technical field

The present invention relates to a kind of analytical approach, in particular, relate to a kind of method for analyzing additive errors of flow field of ultrasonic flowmeter.

Background technology

Ultrasonic flowmeter is a kind of new type of flowmeter that developed recently gets up, higher without crushing, the larger accuracy of bore owing to having, can on existing pipeline, install, multichannel can adapt to the many advantages such as complex flowfield, in flow measurement field, bring into play more and more important effect, particularly in super large caliber flow measurement, thering is outstanding advantage.Ultrasonic flowmeter utilizes forward and reverse mistiming that ultrasound wave is propagated in flow media to measure the line mean flow rate in sound channel, and utilizes face mean flow rate and flow on line mean flow rate (hereinafter referred to as sound channel speed) the weighted calculation cross section to be measured in different sound channels.The accuracy of measurement of flow and the flow field of position are in close relations, this is because cross flow is easily disturbed the reach the standard grade measurement of mean flow rate of sound channel on the one hand, is due to the weighted calculation accuracy of face mean flow rate, to be subject to the impact of sound channel velocity distribution on the other hand.Therefore, ultrasonic flowmeter requires to keep sufficiently long front and back straight length, and to guarantee that its interior flow field does not have cross flow, sound channel velocity distribution is also fairly simple.

The accuracy of measurement of ultrasonic flowmeter and its interior flow field are in close relations, upstream and downstream choked flow piece and probe localized indentation male structure all can affect its interior flow field and then produce additive errors of flow field, the installation of stipulating multichannel flowmeter in measurement verification regulations JJG1030-2007 need to guarantee the flow development length of 5D after front 10D, otherwise needs the extra additive errors of flow field of considering during uncertainty evaluation.Additive errors of flow field is relevant with the complexity in flowmeter flow field of living in, also relevant with flowmeter channel configuration, although spend the flowmeter actual flow calibration that a large amount of manpower and materials carry out under different mounting conditions, test to analyze additive errors of flow field, a lot of achievements have been obtained, but because the influence factor of additive errors of flow field is numerous and very complicated, can not cover by experiment all mounting conditions and flowmeter configuration, therefore, find suitable method and analyze the major issue that additive errors of flow field becomes the accuracy of measurement that improves ultrasonic flowmeter.

Summary of the invention

The object of this invention is to provide a kind of can be low-cost and obtain fast the pipeline flow field under different condition, and then by the difference of flowmeter indication flow and normal flow relatively, analyze the method for additive errors of flow field.

The invention provides a kind of method for analyzing additive errors of flow field of ultrasonic flowmeter, it carries out fluid dynamic numerical simulation for the liquid flow in flowmeter upstream and downstream certain limit in pipeline; Utilize fluid dynamic numerical simulation to obtain the loose some flow rate information in pipe interior flow field, flow velocity is interpolated in each sound channel of flowmeter, and according to the sound channel speed of each sound channel of flowmeter first principles computations, and then weighted sum obtains indication flow; Main flow flow velocity to the loose point in flowmeter xsect flow field carries out area minute, or the sound channel speed main flow contribution amount that gathers abundant sound channel in xsect flow field is weighted summation, obtains the normal flow in flow field; By analysis, indicate the difference of flow and normal flow to obtain the additive error in flow field.

Wherein, utilize the particular location of direction, unique definite each sound channel of flowmeter in sound channel angle on the centre coordinate, main flow direction, sound channel face of flowmeter in pipeline flow field.

Wherein, based on the loose point of pipeline flow velocity, adopt the pchip interpolation method of conformal shape to calculate the sound channel speed in ultrasonic flowmeter sound channel.

Wherein, utilize vector operation that sound channel speed is decomposed into main flow contribution amount and crossing current contribution amount.

Wherein, the area separating method of normal flow is: first the loose point of xsect is carried out to triangularization subdivision, then the product of the average velocity on all triangles and area is sued for peace.

Wherein, the Gauss integration algorithm of normal flow is: in xsect flow field, gather the sound channel speed main flow contribution amount of a plurality of sound channels, be then weighted average acquisition standard mean flow rate and then obtain normal flow.Described a plurality of number of channels is 36.

Wherein, additive errors of flow field comprises due to the integral error that utilizes the flow in the whole cross section of limited sound channel velocity information integral and calculating to produce with due to the crossing current error of cross flow to the interference formation of flow measurement.

The problem that may occur in stream field additive error assessment of the present invention is analyzed, set up the method for analyzing additive errors of flow field of ultrasonic flowmeter, realized the quick and precisely assessment of additive errors of flow field, this analytical approach has good reference significance to utilizing numerical method to solve flow metering problem.

Accompanying drawing explanation

Fig. 1 flowmeter sound channel numbering and A/B sound channel face nomenclature principle;

The trigonometric ratio integration method of Fig. 2 normal flow;

The relation of Fig. 3 virtual channels number and relative difference;

Fig. 4 additive errors of flow field computing method;

Cross flow in Fig. 5 flowmeter center cross-sectional

The sound channel velocity distribution of Fig. 6 flowmeter;

The additive errors of flow field assessment result of Fig. 7 flowmeter.

Embodiment

Along with the development of computer technology and computing technique, numerical simulation becomes a kind of important research means gradually, and the numerical simulation based on computational fluid dynamics (CFD) is penetrated into each field of engineering technology relevant to fluid gradually.Numerical simulation has advantages of that cost is low and can quick and precisely simulate with respect to traditional test method, and hydrodynamics numerical simulation is combined with the measurement of ultrasonic flowmeter, contributes to improve the measurement accuracy of fluid flow.

Additive errors of flow field refers to normal flow poor that flowmeter is arranged on the indication flow that obtains in certain specific flow field and this flow field, utilizing after CFD technology obtains the loose some flow rate information in this flow field, flow rate information need to be interpolated in the sound channel of flowmeter, and calculate the sound channel speed of each sound channel, then the mean flow rate in cross section to be measured is calculated in weighted sum, and multiplies each other and obtain indicating flow with area; Normal flow needs to divide acquisition by flow velocity being carried out to area at tested point.

In order to calculate the flowmeter indication flow in specific flow field, first need to solve sound channel orientation problem, obtain the coordinate of two end points on sound channel line.Ultrasonic flow rate, in respect of monophony face or the configuration of two-channel face, although flowmeter producer adopts different sound channel naming methods, needs the nomenclature principle of unified sound channel numbering and A/B sound channel face while processing based on numerical value flow field.As shown in Figure 2, the direction that definition two sound channel face intersections point to sound channel Base Serial Number is upper direction to nomenclature principle

the main flow direction of definition Flows is people is in the downstream head of flowmeter direction upward

toward upstream, see, the sound channel of downstream probe on right side is A face, the sound channel of downstream probe in left side is B face, sound channel numbering is followed successively by 1 to n from top to bottom, corresponding sound channel height is from just bearing, as shown in Figure 1, using sound channel A-Path1, A-Path2, A-Path3, A-Path4 and B-Path1, B-Path2, B-Path3, B-Path4 as example.Sound channel angle φ is another key parameter in flowmeter configuration, refers to the acute angle angle of sound channel and main flow direction, adds the center position coordinates of flowmeter

totally four parameters

φ,

just can determine the flowmeter sound channel position of any attitude in three-dimensional flow field.

Definition sound channel direction

for sound channel line upstream probe points to the direction of popping one's head in downstream, in sound channel face, sound channel direction is identical, and monophony flow meter only has a sound channel direction

two-channel face flowmeter has two sound channel directions

with

so the coordinate of two end points of sound channel line is

${\stackrel{\→}{P}}_{d,u}=\stackrel{\→}{x}+\stackrel{\→}{u}\·{\mathrm{Rt}}_i\±\stackrel{\→}{l}\·R\sqrt{1-t_i^2}/\sin \mathrm{\φ}---\left(1\right)$

In formula, R is pipeline section radius, t _ifor relative sound channel height, Rt _ifor actual sound channel height,

for half length of this sound channel, sign is downstream and the upstream end points of corresponding sound channel respectively.The angular quadrature scheme that ultrasonic flowmeter adopts is different, relatively sound channel height t _idifference, Gauss-Jaccobi angular quadrature scheme is the angular quadrature scheme of appointment in international rules IEC60041 and ASME PTC18, the form with list in rules has provided t _inumerical value, in fact also can be formulated as

$t_i=\cos \frac{\mathrm{i\π}}{N+1},i=\mathrm{1,2},...,N---\left(2\right)$ In formula, the channel number that N is flowmeter.

Any attitude flowmeter sound channel direction vector

calculating more complicated, can solve by the relative position relation of it and known direction.First sound channel direction is vertical with upper direction,

the angle of its secondary channel direction and main flow direction is sound channel angle,

go up in addition direction vertical with main flow direction,

consider that again three vectors are unit vector,

six formula simultaneous solution equations can obtain thus

its three components are

${\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="HSB00000736197300041.png"\; state="\{\{state\}\}">l</figure-callout>}}_1=((f_1(u_2^2+u_3^2)-u_1(f_2{u}_2+f_3{u}_3))\cos \mathrm{\&phi;}+(f_2{u}_3-f_3{u}_2){\mathrm{\&sigma;}}_2)/{\mathrm{\&sigma;}}_2$

${\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="HSB00000736197300041.png"\; state="\{\{state\}\}">l</figure-callout>}}_2=((f_2(u_1^2+u_3^2)-u_2(f_1{u}_1+f_3{u}_3))\cos \mathrm{\&phi;}-(f_1{u}_3-f_3{u}_1){\mathrm{\&sigma;}}_1)/{\mathrm{\&sigma;}}_2---\left(3\right)$

${\mathrm{<figure-callout\; id="3"\; label="l"\; filenames="HSB00000736197300041.png"\; state="\{\{state\}\}">l</figure-callout>}}_3=((f_3(u_1^2+u_2^2)-u_3(f_1{u}_1-f_2{u}_2))\cos \mathrm{\&phi;}+(f_1{u}_2-f_2{u}_1){\mathrm{\&sigma;}}_1)/{\mathrm{\&sigma;}}_2$

In formula, parameter σ ₂=(f ₁u ₂-f ₂u ₁) ²+ (f ₁u ₃-f ₃u ₁) ²+ (f ₂u ₃-f ₃u ₂) ², parameter that sign is corresponding is two sound channel face A/B.Can utilize multiplication cross to judge σ ₁sign and the corresponding relation of sound channel A/B face, due to multiplication cross corresponding be right-handed system,

point to left side, so according to nomenclature principle utilization above $(\stackrel{\&RightArrow;}{f}\&times;\stackrel{\&RightArrow;}{u})\&CenterDot;\stackrel{\&RightArrow;}{l}=(f_2{u}_3-f_3{u}_2){\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="HSB00000736197300041.png"\; state="\{\{state\}\}">l</figure-callout>}}_1+(f_3{u}_1-f_1{u}_3){\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="HSB00000736197300041.png"\; state="\{\{state\}\}">l</figure-callout>}}_2+(f_1{u}_2-f_2{u}_1)l_3---\left(4\right)$ Judge, make

for on the occasion of direction vector

corresponding is B sound channel,

for negative value

corresponding is A sound channel.

For the flowmeter of liquid medium, flow velocity is much smaller than the velocity of sound, and sound channel is straight line, if the line mean flow rate in sound channel is ? in sound channel direction

on projection and sound channel speed

projection in sound channel direction equates, so sound channel velocity magnitude can be expressed as by the form of vector dot product

$v_{m,i}=({\stackrel{\&RightArrow;}{v}}_i\&CenterDot;\stackrel{\&RightArrow;}{l})/(\stackrel{\&RightArrow;}{f}\&CenterDot;\stackrel{\&RightArrow;}{l})---\left(5\right)$

Therefore, the extraction of sound channel speed is most important is exactly the line mean flow rate obtaining on sound channel line

after sound channel line position is determined by two-end-point coordinate, the loose spot speed in three-dimensional flow field can be interpolated on sound channel line, line mean flow rate

be not the arithmetic mean of each point three-dimensional flow on sound channel line, but need to carry out formula fitting and ask its line integral to obtain it.Fit procedure has adopted the PCHIP method of conformal shape, and problem is over-evaluated or underestimated in the part of having avoided linear fit to bring.

Formula (5) shows not only to have comprised in sound channel speed the contribution of axia flow, has also comprised the contribution of cross flow, and when without cross flow, sound channel speed is exactly the flow velocity of main flow direction, and this is also the ideal situation of ultrasonic flowmeter measuring flow.So can be by sound channel speed v _{m, i}be divided into artificially main flow contribution amount

with crossing current contribution amount v _{c, i}=v _{m, i}-v _{a, i}two parts, the former is the flow velocity that flowmeter will be measured, the latter is the interference volume of cross flow to flowmeter survey flow.In the sound channel speed v that obtains different sound channels _{m, i}afterwards, according to the ultimate principle of ultrasonic flowmeter, indication flow Q can obtain according to the mode of weighted sum,

$Q=A\&CenterDot;\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_i\&CenterDot;v_{m,i}---\left(6\right)$

In formula, the cross-sectional area that A is pipeline, ω _ifor weight coefficient, with relative sound channel height t _icorresponding one by one, in rules, the weight coefficient of Gauss-Jaccobi angular quadrature scheme is

${\mathrm{\&omega;}}_i=\frac{2}{N+1}{\sin }^2\frac{\mathrm{i\&pi;}}{N+1},i=\mathrm{1,2},...,N---\left(7\right)$

Due to sound channel speed v _{m, i}can be decomposed into main flow contribution amount v _{a, i}with crossing current contribution amount v _{c, i}therefore indication flow Q also can be decomposed into main flow contribution amount Q _awith crossing current contribution amount Q _ctwo parts.

Normal flow refers to actual flow corresponding to this flow field, in other words for the loose point of each xsect of flow field main flow flow velocity carries out area minute resulting flow.While utilizing CFD method simulation additive errors of flow field, speed entrance adopts equally distributed flow conditions, and with this flow relocity calculation normal flow, may cause normal flow to have certain deviation, entrance flow field need to can attain full development through tens times of diametral distances in addition, also there are differences with expectation flow field, therefore entrance velocity flow profile is appointed as full-blown velocity flow profile or other given flow rate are distributed as good.

For the area of mainstream speed on computational flow xsect divides, loose point on cross section can be carried out to triangular mesh, as shown in the figure, average velocity in each triangle area is the arithmetic mean of its three summit mainstream speeds, leg-of-mutton area can be calculated by the multiplication cross of its both sides vector, therefore the product of the average velocity on all triangles and area is sued for peace and is the flow on xsect.In addition, according to Gauss-Jaccobi angular quadrature scheme, in xsect flow field, take fully enough virtual channels, calculate the main flow contribution amount of sound channel speed, and weighted average calculation flow, figure has provided and has utilized flow that Gauss (Gauss) integration of different channel number obtains and the relative difference of trigonometric ratio integration flow, visible 36 sound channels can be approached area shunt volume, and its difference is less than 0.05%, can be directly as normal flow.

Additive errors of flow field is indication flow Q and normal flow Q _spoor, obtaining Q and Q _sdirect computational flow additive error afterwards.Due to indication flow, Q can be decomposed into main flow contribution amount Q _awith crossing current contribution amount Q _ctwo parts, therefore additive errors of flow field also can be decomposed into integral error (Q _a-Q _s)/Q _swith crossing current error Q _c/ Q _stwo parts, the former is called integral error is owing to utilizing the flow in the whole cross section of limited sound channel velocity information integral and calculating to produce, what the latter was called crossing current error represents is the interference of cross flow to flow measurement.Ultrasonic flow rate, in respect of the configuration of monophony face and the configuration of two-channel face, can calculate respectively integral error, crossing current error and the total error of two sound channel faces based on CFD flow field, its arithmetic mean is the corresponding error of two-channel face configuration, and circular is shown in Fig. 4.

FLUENT is one of most widely used commercial CFD software, utilize FLUENT can obtain more accurately and easily the pipeline flow field under specified conditions, by the analyzing and processing of data, based on FLUENT, generate, draw and derive the sound channel velocity distribution of any flow meter parameter, and calculate the additive errors of flow field under relevant parameter.

As mentioned above, utilize

φ,

any attitude that can unique definite flowmeter sound channel Deng four parameters, when in practical application, flowmeter level is installed, sound channel attitude is the direction vertically upward in physical space often

on basis around main flow direction

rotate a α angle and obtain, this angle is called established angle α, and is rotated counterclockwise as just to see from downstream toward upstream.Therefore plug-in unit is applied for the convenience of the user, also can pass through

form actual upper direction is set rotation matrix wherein $S\left(\mathrm{\&alpha;}\right)=(1-\cos \mathrm{\&alpha;})\left[\begin{array}{ccc}{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_1^2& f_1{f}_2& f_1{f}_3\\ f_1{f}_2& {\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_2^2& f_2{f}_3\\ f_1{f}_3& f_2{f}_3& {\mathrm{<figure-callout\; id="3"\; label="f"\; filenames="HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_3^2\end{array}\right]+\left[\begin{array}{ccc}\cos \mathrm{\&alpha;}& {\mathrm{<figure-callout\; id="3"\; label="f"\; filenames="HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_3\sin \mathrm{\&alpha;}& -{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_2\sin \mathrm{\&alpha;}\\ -{\mathrm{<figure-callout\; id="3"\; label="f"\; filenames="HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_3\sin \mathrm{\&alpha;}& \cos \mathrm{\&alpha;}& {\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_1\sin \mathrm{\&alpha;}\\ {\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_2\sin \mathrm{\&alpha;}& -{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="HSB00000736197300041.png"\; state="\{\{state\}\}">f</figure-callout>}}_1\sin \mathrm{\&alpha;}& \cos \mathrm{\&alpha;}\end{array}\right]---\left(8\right)$ New upper direction after rotation

participate in sound channel location Calculation.In formula (1), half length of sound channel is

just in time on tube wall, there is the situation of probe indentation in sound channel two-end-point now in order to adapt to flowmeter, half length of sound channel is multiplied by one and is greater than 1 Coefficient m,

assurance also covers computational analysis territory by the flow field of probe indentation part.In fact m is all taken as 1.2, the slightly larger location that can not affect sound channel line.Settings when pipeline section radius R value may be with grid enable in numerical value flow field are slightly variant, specify radius R may cause indicating flow to have deviation herein, need by actual grid Cross section calculation, first by flowmeter center

and main flow direction

obtain flowmeter xsect, then utilize Graham algorithm of convex hull to ask its convex polygon by the loose point coordinate information on this face, then justify matching and can obtain radius R.In addition, at present except Gauss-Jaccobi angular quadrature scheme, partial discharge meter manufacturer has also adopted the angular quadrature scheme of oneself, such as OWICS scheme etc.,

After generating sound channel line, loose some flow velocity in every sound channel is saved in to data file, and from data file, reads these loose some flow rate information and calculate sound channel line mean flow rate

loose point coordinate vector (x, y, z) upward direction in same sound channel projection value xu ₁+ yu ₂+ zu ₃identical, can come accordingly the different sound channels in identical file to distinguish.

Additive errors of flow field obtains sound channel speed main flow contribution amount with 36 virtual channels in calculating and calculates normal flow Q _s, and with the sound channel speed of 36 virtual channels, be interpolated in the actual sound channel of flowmeter and calculate indication flow Q, calculate thus integral error, crossing current error, total error on two sound channel faces of A/B.Interpolation still adopts the PCHIP method of conformal shape, and the deviation of as far as possible avoiding linear interpolation to bring can obtain more approaching actual sound channel velocity distribution curve.

The additive errors of flow field that may cause for typical choked flow piece (elbow, butterfly valve, reducer, increaser), utilizes CFD method to analyze.The flowmeter (as shown in Figure 2) that 1D position, elbow downstream installs of take is example, and flowmeter bore is 1m.

As shown in Figure 5, cross flow is stronger for cross flow result of calculation in flowmeter center cross-sectional, and centre flows downward and by returning both sides, forms the fluidal texture of a binary vortices; Flowmeter established angle α=90 °, φ=45 °, sound channel angle, the projection that the straight line in Fig. 5 is sound channel is located sound channel and is extracted 36 sound channel speed v in virtual channels in flow field _{a, i}and v _{c, i}component, as shown in Figure 6.Can find, under violent crossing current effect, the sound channel speed v on A, B two sides _mwidely different, both average main flow contribution amount v that approach sound channel speed afterwards _a, illustrate that two-sided configuration can offset the mobile interference of parts transversely.

The further additive errors of flow field assessment result of quadraphonic flowmeter from Fig. 7, because sound channel velocity distribution profile differs greatly with being uniformly distributed, therefore the integral error on AB two sides all larger and be on the occasion of, although and crossing current error numeric ratio has negatively obtained good counteracting in AB two sides one positive greatly.Under 1D place, elbow downstream complicated flox condition like this, the additive errors of flow field of the vertical two-sided flowmeter of installing of sound channel is in 1.2% left and right, and visible multichannel flowmeter has good flow field adaptability.

The additive errors of flow field assessment of ultrasonic flowmeter is a complicated job, set up a set of additive error appraisal procedure based on CFD flow field, can carry out data processing to the arbitrary disposition ultrasonic flowmeter of optional position and attitude layout, greatly improve speed and the reliability of evaluation process.In addition, the problem that may occur in indication flow and normal flow calculating process is analyzed, the processing of Similar Problems is had to reference very much.

Although illustrate and described the present invention with reference to embodiments of the invention, but those skilled in the art should understand that, the specific embodiments of enumerating in this instructions or embodiment, only in order to understand technology contents of the present invention, in the case of without departing from the spirit and scope of the present invention, the present invention can carry out multiple change in the form and details.

Claims (4)

1. a method for analyzing additive errors of flow field of ultrasonic flowmeter, carries out fluid dynamic numerical simulation for the liquid flow in flowmeter upstream and downstream certain limit in pipeline; Utilize fluid dynamic numerical simulation to obtain the loose some flow rate information in pipe interior flow field, flow velocity is interpolated in each sound channel of flowmeter, and according to the sound channel speed of each sound channel of flowmeter first principles computations, and then weighted sum obtains indication flow; Main flow flow velocity to the loose point in flowmeter xsect flow field carries out area minute, or the sound channel speed main flow contribution amount that gathers a plurality of sound channels in xsect flow field is weighted summation, obtains the normal flow in flow field; By analysis, indicate the difference of flow and normal flow to obtain the additive error in flow field, additive errors of flow field comprises due to the integral error that utilizes the flow in the whole cross section of limited sound channel velocity information integral and calculating to produce with due to the crossing current error of cross flow to the interference formation of flow measurement; It is characterized in that: the particular location that utilizes direction, unique definite each sound channel of flowmeter in sound channel angle on the centre coordinate, main flow direction, sound channel face of flowmeter in pipeline flow field; Utilize vector operation that sound channel speed is decomposed into main flow contribution amount and crossing current contribution amount; Additive errors of flow field obtains sound channel speed main flow contribution amount with 36 virtual channels in calculating and calculates normal flow, and with the sound channel speed of 36 virtual channels, be interpolated in the actual sound channel of flowmeter and calculate indication flow, calculate thus two integral error, crossing current error, total errors on sound channel face.

2. analytical approach as claimed in claim 1, is characterized in that: the area separating method of normal flow is: first the loose point of xsect is carried out to triangularization subdivision, then the product of the average velocity on all triangles and area is sued for peace.

3. analytical approach as claimed in claim 1, it is characterized in that: the Gauss integration algorithm of normal flow is: in xsect flow field, gather the sound channel speed main flow contribution amount of a plurality of sound channels, be then weighted average acquisition standard mean flow rate and then obtain normal flow.

4. analytical approach as claimed in claim 1, is characterized in that: based on the loose point of pipeline section flow velocity, adopt the pchip interpolation method of conformal shape to calculate the sound channel speed in ultrasonic flowmeter sound channel.

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