CN202974344U - U-shaped channel vertical wall-type measuring flume - Google Patents

Abstract

The utility model discloses a U-shaped channel vertical wall-type measuring flume, which comprises a U-shaped channel of which both sides are both vertical side walls and the bottom part is a smooth and round curved surface. A section in the U-shaped channel is contracted in width to form a throat section; upstream and downstream transition sections of the throat section are both smooth curved surfaces, and an upstream transition section and a downstream transition section are respectively formed. The U-shaped channel vertical wall-type measuring flume also comprises a staff gauge used for measuring water depth in the U-shaped channel. The utility model provides a novel U-shaped channel flow measuring device which is easy in manufacturing and high in measurement accuracy.

Description

The U-shaped canal straight wall type measuring flume

Technical field

The utility model belongs to the open-channel flow field of measuring technique, is specifically related to a kind of U-shaped canal straight wall type measuring flume.

Background technology

The form of open channel section mainly contains rectangular cross section, trapezoidal cross-section, triangular section, parabolic-shaped section and channel section, also has various compound cross-sections.For rectangular cross section, trapezoidal cross-section and triangular section, existing many water-measuring devices, for example be adapted to the long venturi flume of rectangle, rectangle broad-crested weir, rectangle of rectangular canal without larynx section flume, be adapted to trapezoidal long venturi flume, Bashel flume, the triangular cross-section weir of trapezoidal cross-section, be adapted to the long venturi broad-crested weir of triangle of triangular section etc.

Along with the development of operating technique and construction machinery, in recent decades, China greatly develops the U-shaped channel, at this moment has floor area because of the U-shaped channel little, and conveyance capacity is large, is difficult for alluvial, and the strong advantage of frost heaving resistant ability.For the flow measurement problem of U-shaped channel, all carried out research both at home and abroad.For example international standard has been recommended the long venturi flume of a kind of U-shaped (round bottom shape), and it is the Sloping U-Shaped Channel of rectangle for semicircle, top that this flume is adapted to the bottom.China widely applies the U-shaped channel to originate in twentieth century the 1970s and 1980s, and the form of U-shaped channel most of bottoms be circle, top is trapezoidal, and it is rectangle that a small amount of top is also arranged.

Summary of the invention

The purpose of this utility model is to provide a kind of U-shaped canal straight wall type measuring flume, and a kind of novel U-shaped canal capacity measurement mechanism is provided, and easily make, and measuring accuracy is high.

The technical scheme that the utility model adopts is, a kind of U-shaped canal straight wall type measuring flume, comprise that both sides are that upright side walls and bottom are the U-shaped channel of smooth round surface, one section shrinkage in width in the U-shaped channel forms the venturi section, the upstream and downstream transition section of venturi section is smooth curved surface and forms respectively upstream transition section and downstream transition section, also comprises for the water gauge of measuring the depth of water in the U-shaped channel.

Characteristics of the present utility model also are, water gauge is arranged on the U-shaped channel inwall that is positioned at upstream transition section upstream, and perhaps, to being connected with electrofacies communicating pipe, and water gauge is arranged in well logging the U-shaped channel of upstream transition section upstream by level.

The beneficial effect of the utility model U-shaped canal straight wall type measuring flume is:

1, make easily.The bottom of the venturi section of standing crop tank, upstream transition section and water gauge section requires level, and bottom of the present utility model is U-shaped identical bottom former channel, and former channel does not need transformation; Venturi Duan Weizhi wall of the present utility model, the two ends transition section is smooth curved surface, compares with existing U-shaped channel measurement flume with parobolic throat in U shaped channel (the two ends transition section is pinch plane, and the venturi section is para-curve or circle).Make easily.2, the flow measurement precision is high.The utility model has been carried out development test, and actual measured results shows, the error of indication is 3.4%, and the error of indication of existing U-shaped channel measurement flume with parobolic throat in U shaped channel is 4.6%.3, the utility model is long venturi flume, can calculate depth of water discharge relation with boundary layer theory, and existing U-shaped channel measurement flume with parobolic throat in U shaped channel is short venturi flume, and depth of water discharge relation can only be according to different channel specifications, by experiment calibration.

Description of drawings

Fig. 1 is the structural representation of the utility model U-shaped canal straight wall type measuring flume;

Fig. 2 is the vertical view of Fig. 1;

Wherein, 1.U shape channel, 2. upstream transition section, 3. venturi section, 4. downstream transition section, 5. communicating pipe, 6. well logging.

Embodiment

As depicted in figs. 1 and 2, the utility model U-shaped canal straight wall type measuring flume, comprise that both sides are that upright side walls and bottom are the U-shaped channel 1 of smooth round surface, one section shrinkage in width in U-shaped channel 1 forms venturi section 3, the upstream and downstream transition section of venturi section 3 is smooth curved surface and forms respectively upstream transition section 2 and downstream transition section 4, also comprises for the water gauge of measuring the U-shaped channel 1 interior depth of water.Water gauge is arranged on U-shaped channel 1 inwall that is positioned at upstream transition section 2 upstreams, and perhaps, to being connected with well logging 6 communicating pipe 5, and water gauge is arranged in well logging 6 the U-shaped channel 1 of upstream transition section 2 upstreams by level.

In the utility model, the length L=1.25B of venturi section 3 ₀, the length L of upstream transition section 2 and downstream transition section 4 ₁=L ₂=0.7B ₀, the equation of upstream transition section 2 and downstream transition section 4 is

$\frac{x^2}{{\left(0.7B_0\right)}^2}+\frac{y^2}{{[(B_0-b)/2]}^2}=1---\left(1\right),$

In formula, b is the venturi width of venturi section 3; B ₀Be the ratio H/(2R of the dark H of canal with two times of radiuses)=width of 0.82 canal depths, R is the radius of U-shaped channel 1, B ₀Can calculate with following formula

$B_0=2R\sin \left(\frac{\mathrm{\θ}}{2}\right)+2(H-T)\tan \mathrm{\α}---\left(2\right),$

$T=R(1-\cos \frac{\mathrm{\θ}}{2})---\left(3\right),$

In formula, θ is central angle; The height that T is U-shaped channel 1 arc section and top straight-line segment tangent place at the bottom of the canal; α is camber angle.

Water gauge is located at U-shaped canal straight wall type measuring flume import upstream 1.5B ₀The place, be center elevation at the bottom of water gauge section part canal its zero point.

The venturi width of U-shaped canal straight wall type measuring flume can design according to the flow that channel passes through, and its shrinkage ratio λ is

λ＝b/(2R) （4），

When canal equaled the channel diameter deeply, the utility model cell body height calculated with following formula, and at this moment, flume top and canal top are same high:

$H_L=R[1+\sqrt{{1-\left(\frac{b}{2R}\right)}^2}]---\left(5\right),$

During deeply greater than diameter, first use formula (5) to calculate calibrated altitude when canal, insufficient section available standards prefabricated component is increased to the canal heights of roofs.

During deeply less than diameter, the flume height can equal diameter deeply by canal to be processed when canal.

The calculating of the utility model U-shaped canal straight wall type measuring flume water gauge height.For the water gauge that is engraved on U-shaped channel cell wall, the computing formula that the pass of water gauge height and arc length S ties up to the following arc length in point of contact is

S＝Rθ ₁ （6），

θ in formula ₁With the pass of water gauge vertical height h be

${\mathrm{\θ}}_1=2\arcsin \left(\sqrt{\frac{h}{2R}}\right)---\left(7\right),$

For point of contact above water gauge length computation formula be:

$S=\mathrm{R\θ}+\frac{h-T}{\cos \mathrm{\α}}---\left(8\right),$

In formula, point of contact height T calculates with formula (3), and θ is central angle.α is the channel inclination angle.

Vertical water gauge for being arranged in well logging directly carves the water gauge height by size.

Principle of work of the present utility model is: when current pass through the U-shaped canal straight wall type measuring flume, because venturi section 3 has contraction, current in upstream U-shaped channel 1 are unhurried current, and the current of venturi section 3 are due to the change of cross-sectional area, current are from gradually becoming less than critical depth of water greater than critical depth of water, make the water surface sharply land, form water-head in the U-shaped channel 1 of upstream and venturi section 3, the flow formula that utilizes energy equation can derive by the U-shaped canal straight wall type measuring flume is

In formula, Q is flow; B is the venturi width; G is acceleration of gravity; R is the radius of U-shaped channel; λ=b/ (2R) is shrinkage ratio; α is the kinetic energy correction factor;

Be efflux coefficient; H ₀Be the upstream gross head.

The flow formula of general quantity tank is

$Q=\mathrm{mb}\sqrt{2g}{H}_0^{3/2}---\left(10\right),$

In formula, m is coefficient of flow.

Comparison expression (9) and formula (10) can get U-shaped canal straight wall type measuring flume coefficient of flow

Wherein, for kinetic energy correction factor α, generally be taken as 1.Gross head is

$H_0=H+\frac{Q^2}{2g{A}_0^2}---\left(12\right),$

In formula, H is the upstream depth of water; A ₀Discharge section area for flume water gauge place.

If known flow rate coefficient

With formula (12) substitution formula (11), get final product the calculated flow rate Coefficient m, coefficient of flow m substitution formula (10) is obtained the flow that passes through in the utility model; Perhaps, directly use formula (9) calculated flow rate.

For long venturi flume, international standard ISO handbook 16 recommends to ask with boundary layer theory the flow of throughput tank.And provided the flow formula of rectangle, trapezoidal, triangle, the long venturi flume of standard channel section (bottom is for semicircle, and top is rectangle).The U-shaped canal straight wall type measuring flume belongs to long venturi flume, also can the application boundary shelf theory inquire into flow formula.

Boundary layer theory be 1904 Prandtl (L.Prandtl) put forward.The advantage of boundary layer theory is: as long as after the physical dimension of flume determines, just can directly calculate the stage discharge relation of flume, a large amount of studies show that, has enough precision with the flow that passes through in boundary layer theory calculated amount tank.

The flow formula of being tried to achieve the U-shaped canal straight wall type measuring flume by boundary layer theory is

$Q={\left(\frac{2}{3}\right)}^{3/2}\sqrt{g}(b-2{\mathrm{\&delta;}}_1){(H+\frac{{\mathrm{<figure-callout\; id="2"\; label="Q"\; filenames="HDA00002449439100011.png,HDA00002449439100012.png"\; state="\{\{state\}\}">Q</figure-callout>}}^2}{2g{A}_0^2}-\frac{C}{b-2{\mathrm{\&delta;}}_1})}^{3/2}---\left(13\right),$

$C=R(1-\sqrt{1-{\mathrm{\&lambda;}}^2})(b-2{\mathrm{\&delta;}}_1)+\frac{\mathrm{\&pi;}}{45}R{\mathrm{\&delta;}}_1\arctan \frac{1-\sqrt{1-{\mathrm{\&lambda;}}^2}}{\mathrm{\&lambda;}}-R^2(\arcsin \mathrm{\&lambda;}-\mathrm{\&lambda;}\sqrt{1-{\mathrm{\&lambda;}}^2})---\left(14\right),$

In formula, δ ₁Displacement thickness for the boundary layer.Can be found out by formula (14), when build one timing of U-shaped canal straight wall type measuring flume, R, λ are known number.The displacement thickness δ in boundary layer ₁Formula with Harrison calculates

(1) work as R _eR _et, be turbulent boundary layer

${\mathrm{\&delta;}}_1=L[(1-\mathrm{\&gamma;}){\left(\frac{{\mathrm{\&delta;}}_1}{L}\right)}_L+\mathrm{\&gamma;}\left(\frac{R_e-R_{\mathrm{et}}}{R_e}\right){\left(\frac{{\mathrm{\&delta;}}_1}{L}\right)}_T]---\left(15\right),$

In formula ${({\mathrm{\&delta;}}_1/L)}_L=1.72/\sqrt{R_e}---\left(16\right),$

$\ln (1-\mathrm{\&gamma;})=-0.412{[(R_e-R_{\mathrm{et}})/\left(5\sqrt{R_e}\right)]}^{1/2}---\left(17\right),$

(δ wherein ₁/ L) _T(L/K _s) function, as (L/K _s)≤3.0 * 10 ⁴The time

${({\mathrm{\&delta;}}_1/L)}_T=[6.92{(R_e{K}_s/L+6)}^{-0.841}+1]\{0.0952{\left[\frac{L}{K_s}(1-R_{\mathrm{et}}/R_e)\right]}^{-0.417}+0.0013\}---\left(18\right),$

As (L/K _s) 3.0 * 10 ⁴The time

${\left(\frac{{\mathrm{\&delta;}}_1}{L}\right)}_T=[0.15{(R_e-R_{\mathrm{et}})}^{-0.303}+0.0008]\{0.445{[\frac{L/K_s}{0.0834R_e{(R_e-R_{\mathrm{et}})}^{-0.222}+0.006R_e}+0.2]}^{-0.727}+1\}---\left(19\right),$

(2) work as R _e＜R _etThe time, be boundary layer of laminar flow

${\mathrm{\&delta;}}_1=1.72L/\sqrt{R_e}---\left(20\right),$

In formula, R _eBe Reynolds number; R _ek=3 * 10 ⁵Critical Reynolds number when changing turbulent flow into for laminar flow; L is the venturi length of U-shaped canal straight wall type measuring flume; K _sBe absolute roughness height, for general concrete surface, K _s=0.3 ~ 0.6mm.

Reynolds number calculates with following formula

$R_e=\frac{L}{v}{\left(\frac{\mathrm{gQ}}{b}\right)}^{1/3}---\left(21\right),$

In formula, v is the coefficient of viscosity.For the depth of water before known groove, Reynolds number also available following formula calculates

$R_e=\frac{\mathrm{<figure-callout\; id="2"\; label="L\; v"\; filenames="HDA00002449439100011.png,HDA00002449439100012.png"\; state="\{\{state\}\}">L</figure-callout>}}{v}\sqrt{\frac{2}{3}\mathrm{gH}}---\left(22\right),$

For boundary layer displacement thickness δ ₁, the method that also can adopt international standards is calculated, and for the smooth flume surface in laboratory, gets δ ₁/ L=0.003; The prototype amount of concrete tank of effects on surface troweling, δ ₁/ L=0.005.

Operation experiments step of the present utility model is:

1. according to the specification of U-shaped channel 1, determine minimum and maximum flow (normal depth of flow discharge relation) by designing in U-shaped channel 1.

2. according to minimum and maximum flow, preset the width of venturi section 3, obtain shrinkage ratio λ.

3. determine B with above-mentioned formula (2), (3) ₀, determine the curvilinear equation of the utility model upstream and downstream transition section with formula (1).

4. determine venturi section 3 length L=1.25B ₀

5. determine upstream transition section 2 and downstream transition section 4 length L ₁=L ₂=0.7B ₀

6. determine water gauge position L _a=1.5B ₀

7. determine the height of the utility model cell body with formula (5).

8. get 20 ° of C of normal temperature, ask coefficient of viscosity ν.

9. suppose a depth of water H, and calculate Reynolds number.

10. at K _sGet an absolute roughness height K in=0.3 ~ 0.6mm scope _s

11. with venturi length L, Reynolds number R _eWith absolute roughness K _sFormula is with the displacement thickness δ of international standard formula computation bound layer ₁

12. the displacement thickness δ with shrinkage ratio λ, boundary layer ₁Ask C with the radius R of U-shaped channel with the international standard formula.

13. the discharge section area A at calculated amount water gauge place ₀

14 with C, b, δ ₁, H, A ₀Substitution formula (13) is asked flow.

15. after obtaining one group of flow, compare with the minimum and maximum flow that requires, as both meet the requirements for required, as nonconforming, again suppose the width of venturi section 3, repeat above design procedure, until reach requirement.

Claims (2)

1. U-shaped canal straight wall type measuring flume, it is characterized in that, comprise that both sides are that upright side walls and bottom are the U-shaped channel (1) of smooth round surface, one section shrinkage in width in U-shaped channel (1) forms venturi section (3), the upstream and downstream transition section of described venturi section (3) is smooth curved surface and forms respectively upstream transition section (2) and downstream transition section (4), also comprises for the water gauge of measuring the interior depth of water of U-shaped channel (1).

2. according to U-shaped canal straight wall type measuring flume claimed in claim 1, it is characterized in that, described water gauge is arranged on U-shaped channel (1) inwall that is positioned at upstream transition section (2) upstream, perhaps, the U-shaped channel (1) of described upstream transition section (2) upstream is connected with well logging (6) to communicating pipe (5) by level, and described water gauge is arranged in well logging (6).

Images