WO1994024522A1 - Procede, agencement et dispositif permettant de determiner l'ecoulement d'un liquide a surface libre - Google Patents

Procede, agencement et dispositif permettant de determiner l'ecoulement d'un liquide a surface libre Download PDF

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Publication number
WO1994024522A1
WO1994024522A1 PCT/DE1994/000445 DE9400445W WO9424522A1 WO 1994024522 A1 WO1994024522 A1 WO 1994024522A1 DE 9400445 W DE9400445 W DE 9400445W WO 9424522 A1 WO9424522 A1 WO 9424522A1
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WO
WIPO (PCT)
Prior art keywords
gas
channel
gas bubbles
bubbles
blind hole
Prior art date
Application number
PCT/DE1994/000445
Other languages
German (de)
English (en)
Inventor
Wolfgang Frey
Original Assignee
Wolfgang Frey
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE19934313681 external-priority patent/DE4313681C1/de
Priority claimed from DE4313682A external-priority patent/DE4313682C2/de
Application filed by Wolfgang Frey filed Critical Wolfgang Frey
Publication of WO1994024522A1 publication Critical patent/WO1994024522A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/002—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow wherein the flow is in an open channel
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/704—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter
    • G01F1/708—Measuring the time taken to traverse a fixed distance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/704—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter
    • G01F1/708—Measuring the time taken to traverse a fixed distance
    • G01F1/7086—Measuring the time taken to traverse a fixed distance using optical detecting arrangements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
    • G01P5/001—Full-field flow measurement, e.g. determining flow velocity and direction in a whole region at the same time, flow visualisation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
    • G01P5/18—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the time taken to traverse a fixed distance
    • G01P5/20—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the time taken to traverse a fixed distance using particles entrained by a fluid stream

Definitions

  • the invention relates to a method for determining the outflow of a liquid flowing with a free mirror in a channel using gas bubbles as the measuring medium, and to an arrangement and a device for carrying out the method.
  • velocity-area methods are used, which measure the velocity field in a channel flow at great expense for various outflows in order to derive a water level-outflow relationship, i.e. to construct a discharge curve and ultimately to be able to draw conclusions about the discharge curve.
  • the invention is therefore based on the object of creating a method for determining the outflow with a high temporal resolution of the type mentioned at the outset, with which outflows can be carried out directly and without loss with a high degree of accuracy, in particular at low flow rates, in a clear mirror flowing liquids can be determined. Furthermore, the invention is directed to an arrangement for carrying out the method and a device for generating defined gas bubbles as a measuring medium for the method.
  • the solution according to the invention in the method mentioned at the outset is that a time sequence of individual gas bubbles is generated by means of diffusers which are spatially distributed over a cross-sectional area of the bottom of the channel, the gas bubbles being of such a size that they have an almost constant rate of climb of ascending the bottom of the channel up to its surface, at least one image of the horizontal drift of the gas bubbles on the surface of the channel is recorded by means of at least one optical image sensor arranged outside of the liquid, and that the at least one image taken to determine the outflow of the channel is evaluated by means of an image processing unit.
  • an essential element of the invention for the precise determination of the outflow over an entire cross-sectional area having a two-dimensional flow profile of a liquid flowing with a free mirror by means of the rapid measuring method according to the invention is the suitable size of the gas bubbles , which is to be chosen in such a way that the gas bubbles integrate the height profile of the flow velocity in the flume in the vertical line during the ascent.
  • the drift measured on the surface serves as the measured value for the path integral of a gas bubble.
  • the outflow is determined from the measured transverse distribution of the drift of gas bubbles from many diffusers.
  • the spatial arrangement of the diffusers on the bottom of the channel can be made as desired.
  • the Image processing and evaluation for determining the outflow is advantageously simplified in that the diffusers are arranged next to one another in a row running transversely to the flow direction of the channel.
  • the method according to the invention can be used to measure the outflow of any liquids.
  • the most important practical application is that for measuring the runoff of channels, the majority of which consists of water, the other components being admixtures, impurities or foreign substances. In these cases, it is generally the cheapest for cost reasons if the gas bubbles are air bubbles. In special applications, however, other gases, such as Helium or nitrogen can be used.
  • any gas can be used, the bubbles of which meet the requirements with regard to the rate of ascent and the compatibility with the liquid.
  • air bubbles are mentioned in the following, this applies to any gas bubbles without restriction of generality with corresponding modifications.
  • Exemplary applications of air bubbles in water are mentioned.
  • the size of any gas bubbles in any liquids can be measured in a corresponding manner. If necessary, experimental investigations of the rate of ascent can also be carried out for this purpose.
  • an advantageous embodiment of the invention is that the air bubbles have an equivalent bubble diameter of between 3 mm and bubble volumes of the same volume and 10 mm, particularly advantageously about 4.5 mm. These air bubbles meet in a particularly good way the requirement of an approximately constant rate of climb.
  • a video camera for example a CCD camera
  • the optical image recorder can have the advantage that the image can be processed and evaluated digitally.
  • the advantages achieved by the invention are, in particular, that with the method according to the invention and the arrangement according to the invention described below, backflow phenomena and backflows, such as occur regularly in sewer systems, can also be detected, and the direction of flow can be determined and the volume flow in the relevant direction can be determined at any time.
  • the measuring method according to the invention allows the detection of unsteady flows due to the very short measuring time. It measures the discharge directly, without the knowledge of the flow velocity and the flow cross-section being required. Depending on the spatial arrangement of the diffusers, the entire flow cross section can be recorded at the same time without impairing any shipping traffic.
  • the diffusers it is also possible not to arrange the diffusers over the entire cross-section of the channel or not to arrange them directly on the bottom of the channel and to take account of the cross-sectional components not recorded during the measurement in the calculation of the discharge.
  • the arrangement of the diffusers at a distance from the base can be particularly advantageous if the gas bubble formation or its ascent would be disturbed by special features of the base of the channel, such as, for example, existing silt or vegetation.
  • a further advantage of the invention is that influences such as the density and the suspended matter content of the liquid and the temperature of the measuring medium can be taken into account.
  • outflows at the respective measuring location, the direction of flow and thus also occurring transient flow processes can thus be recorded over any period of time.
  • outflows can be measured and recorded directly in natural as well as in artificial channels, regardless of their flow cross-sectional geometry.
  • the proposed invention can thus be used in rectangular, triangular, trapezoidal and, with corresponding adaptations, also in circular, egg-shaped and channel-shaped channel cross sections.
  • the discharge can also be determined and measured in graded, structured discharge cross-sections across the width of the channel.
  • the invention is particularly suitable for applications in which the liquid flows slowly, that is to say for channels in which the flow velocity of the liquid is less than 1 m / s, in particular less than 0.05 m / s.
  • the operating areas of municipalities, municipalities and cities responsible for the wastewater can not only use the measuring method to measure the outflows at any place in the collecting channels of the city drainage system, but also quantify the proportion of untreated wastewater behind rain retention basins and rain overflow basins after heavy rainfall, the receiving water must be fed directly.
  • Industrial companies can use the measuring method not only to document the wastewater discharges into the receiving water that have been approved for them, but also to control the outflows in internal water cycles.
  • the volume flow determines the quality and efficiency of the recovery process. It can be determined with the measuring method in the free-flowing channels of such companies with high measuring accuracy.
  • Outflows from built-up and paved areas are fed to the sewage treatment plants or directly to the receiving waters in artificial free-flowing channels. They can be determined with the measuring method at the point of introduction.
  • the water drainage from rinsing fields depends on the type of silt rinsing and the duration of storage of the silt. This unsteady outflow can be determined in the collecting channels which follow the flushing springs using the measuring method. The same applies to the drainage drains from landfill leachate and the wastewater drains arising from the dewatering of sewage sludge.
  • Precise discharge measurements are required not only in the field of wastewater technology.
  • Another area of application for the discharge measurement method is in the discharge measurement of additional water to increase the low water level of the receiving water.
  • the aim here is to optimize the proportion of high-quality feed water that is often of drinking water quality.
  • the inflow into the receiving water can be measured directly in front of the discharge structures.
  • a further area of application of the discharge measurement method according to the invention is the discharge measurement in supply channels in the case of overflow irrigation (wild trickling, regulated surface flooding, etc.), strip and furrow irrigation in cultivated agriculture.
  • overflow irrigation wild trickling, regulated surface flooding, etc.
  • strip and furrow irrigation in cultivated agriculture.
  • the watering is to be controlled in such a way that the plant water requirements are met.
  • the diffusers are arranged next to one another in a row running transversely to the flow direction of the channel or that an illumination device is provided for illuminating the surface of the channel in the area of the ascending gas bubbles.
  • a further advantageous embodiment can be that a support structure for holding at least one of the at least one image sensor is provided in a position from which an image of the ascending gas bubbles can be taken.
  • the position of the image sensor is preferably in the air space above the surface of the liquid. If this is not possible, the image sensor can also be arranged on the side of the channel, for example on the bank.
  • a storage medium can be connected to the at least one image recorder, with which the at least one recorded image can be stored for determining the outflow of the channel and can be supplied to an image processing unit.
  • Injection cannulas from 0.2 mm diameter From 0.2 mm diameter.
  • the invention is therefore based on the further problem of creating a device for carrying out the method according to the invention with a diffuser for generating gas bubbles of defined and constant size in a liquid, to which the bubbles required to generate a clear bubble trace are generated in sufficient numbers per unit of time form, whereby it is ensured that the bubble formation is absolutely uniform in size and frequency.
  • a diffuser which has a gas inlet with an inlet opening for the supply of the gas, a gas outlet with an outlet opening for the outlet of the gas bubbles and a gas channel connecting the gas inlet and the gas outlet, in the gas channel one in the flow direction of the gas a throttle located downstream of the inlet opening for throttling the gas flow is arranged with a throttle opening, part of the gas channel being formed by a blind hole which extends from its bottom towards its open end in the direction of the gas outlet extends, the inlet point of the gas channel, at which the gas flowing from the throttle downstream into the blind hole enters the blind hole, being arranged at a point in the blind hole from which the gas at least a portion of the blind hole downstream in the direction of flows through the gas outlet, and wherein the blind hole at the inlet point an S acklochquerites which is larger than the opening area of the throttle opening.
  • the opening area of the throttle opening is in the range from 0.002 mm 2 to 0.785 mm 2 .
  • the blind hole advantageously has a diameter in the range from 1 mm to 8 mm, preferably approx. 2 mm, and a length in the range from 2 mm to 80 mm, preferably approx. 14 mm.
  • the gas outlet comprises an expansion recess arranged in the diffuser, which has an inner end upstream of the gas flow and a downstream outer end, the open end of the blind hole being connected to the inner end of the expansion recess and the diameter of the expansion recess at the outlet opening of the gas outlet is larger than the diameter of the open end of the blind hole.
  • the expansion recess advantageously has a diameter between 2 mm and 10 mm, preferably approximately 3 mm, and a length in the flow direction of the gas between 1 mm and 15 mm.
  • the expansion recess can be cylindrical. In a preferred embodiment, however, it can also have a course, for example conical, which widens from its inner end to its outer end. It can be advantageous if the diameter of the inner end of the expansion recess corresponds to that of the open end of the blind hole.
  • the expansion recess advantageously has a diameter in the range between 1 mm and 8 mm, preferably approximately 2 mm, at its inner end and a diameter in the range between 2 mm and 10 mm, preferably approximately 4 mm, at its outer end.
  • the length of the expansion recess is advantageously approximately 1 mm.
  • the throttle and the blind hole and, if appropriate, the expansion recess be embedded in a carrier part. are worked.
  • the carrier part is shaped like a screw and has a thread for screwing in.
  • the carrier part can be made of steel, stainless steel, plastic or another material suitable for use in the respective liquid and with the respective gas, for example made of non-ferrous metal, glass or ceramic.
  • the throttle has a cannula.
  • a wire is arranged in the opening of the cannula. The wire reduces the opening cross section of the cannula, which is advantageously in the range from 0.007 mm 2 to 0.013 mm 2 , preferably from approximately 0.01 mm 2 , the wire having a cross section in the range from 0.0070 mm 2 to 0.0086 mm 2 , preferably about 0.0078 mm 2 .
  • the cannula can have an opening cross section in the range from 0.002 mm 2 to 0.003 mm 2 , preferably from approximately 0.0025 mm 2 .
  • the cannula can advantageously consist of stainless steel, plastic or glass.
  • Stainless steel, spring steel or glass can preferably be provided for the material of the wire.
  • the diffuser according to the invention has the advantage that it is necessary to produce a clear bubble trace A sufficient number of gas bubbles can be formed per unit of time, ensuring that the size and frequency of the bubble formation is uniform so that it can supply the gas bubbles required as the measuring medium in the method and the arrangement according to the invention as the measuring medium.
  • it is preferably designed such that the gas bubbles generated have an equivalent bubble diameter, based on the volume of the same bubbles, of between 1 mm and 20 mm, preferably between 3 mm and 10 mm and particularly preferably about 4.5 mm.
  • the measurement can be carried out on the basis of the preferred dimensions described or by experimental investigations.
  • Fig. 1 is a graphical representation of the vertical
  • FIG. 3 shows an enlarged detail "X" according to FIG. 2,
  • FIG. 5 an air bubble depicted as a flattened rotational ellipsoid
  • 6 shows a schematic perspective illustration of the arrangement according to the invention for carrying out the method
  • FIG. 8 shows a basic illustration of a diffuser according to the invention in section
  • FIG. 10 shows a basic illustration of a further modified diffuser according to the invention in section.
  • FIG. 1 shows a graphical representation of the vertical flow velocity profile VP in a channel as a function of the height y between the sole 8 and the surface 13.
  • FIG. 2 the characteristic ascent path AB of air bubbles 12 in a water channel is shown in FIG Invention shown.
  • the air bubbles 12 are driven away by the drift S by the liquid flow on their way from the sole 8 to the surface 13.
  • a detail at X in FIG. 2, which is explained in more detail below, is shown in FIG. 3.
  • the measuring method according to the invention is based on the principle of the so-called "integrating Schwi measurement".
  • gas bubbles of a suitable size rise from the bottom 8 in a channel 14, being driven off at every point during the ascent by the amount which corresponds to the local speed (cf. FIG. 2).
  • At least one image of the ascending gas bubbles floating on the surface 13 is recorded, for example with the aid of a video camera 5, and the image is then digitally processed.
  • the method measures the discharge directly, without knowing the flow rate and the flow cross-section.
  • the method according to the invention is based on physical considerations from the field of fluid dynamics, which are defined by the following equations and illustrated using the graphical representations according to FIGS. 1 to 5:
  • the integral f ds corresponds to the distance S, and represents the drift of an ascending gas bubble reaching the surface (FIG. 2).
  • the specific outflow q is therefore directly proportional to the drift S.
  • 4 shows measurement results of the rate of rise u g of air bubbles 12 in pure and contaminated water (cf. Clift, Grace and Weber, 1978, Bubbles, Drops and Particles. ACADEMIC PRESS, New York, San Francisco, London). 4 shows the rate of climb u s as a function of the equivalent bubble diameter d orf .
  • the entire area shown is divided into three sub-areas, namely in the area Bl of the spherical bubbles, area B2 of the ellipsoid-like bubbles and area B3 of the screen bubbles.
  • the designation DW stands for "distilled water” and the designation LW for "tap water”.
  • the equivalent diameter d orr that an air bubble 12 rising in water may assume to a maximum, so that the bubble still behaves like a rigid ball, is approximately 0.2 mm (cf. BAUER 1971, Basics of Single-Phase and Multi-Phase Flows, Sauerators AG, Aaran).
  • the shear stress at the phase interface inside the bubble causes a circulation flow. Since the velocity gradient at the movable phase interface is smaller than at the rigid one, the shear stress at the interface is reduced and thereby the resistance is reduced. Accordingly, the rate of climb u s of large bubbles is higher than that of rigid balls of the same shape.
  • the bubble deforms with a further increase in the equivalent bubble diameter d or to a flattened ellipsoid of revolution (FIG. 5).
  • the rate of climb u s of this bubble two influences acting in the opposite direction must be taken into account.
  • the mobility of the phase surface contributes to increasing the rate of climb u s
  • the vortices which occur periodically behind the flattened ellipsoid of rotation cause a tumbling movement, so that the bubble rises on a screw-like path.
  • the rate of climb is u s thus smaller than the actual web speed (see FIG. BAUER, 1971, Fundamentals of Single-phase and multi-phase flows, Sauerators AG, Aaran).
  • a further increase in the equivalent bubble diameter d__ leads to the conversion of the bubble shape from the ellipsoid of rotation to the so-called "umbrella bubble” and an increase in the rate of climb.
  • ⁇ is the surface tension between water and air (cf. CLIFT, GRACE, WEBER, 1978 , Bubbles, Drops and Particles; ACADEMIC PRESS, New York, San Francisco, London).
  • the method of determining the discharge according to the invention has been successfully investigated for the measurement of small and at the same time fluctuating discharges with changing water levels in the following example.
  • the measurements simulate a typical use of the discharge measurement method, as it would result in the different areas of application mentioned above.
  • FIG. 6 An advantageous arrangement for carrying out the method according to the invention is described below with reference to FIG. 6.
  • a channel 14 of flowing water with the surface 13 is shown.
  • a plurality of diffusers 1 are arranged side by side by means of a diffuser holder 2.
  • the diffusers 1 are connected to a compressed air supply unit 4 by means of a compressed air line 3.
  • a video camera 5 and a microprocessor 6 connected to it and an illumination device 7 are provided.
  • the arrangement can be arranged, for example, in the area of a bridge.
  • a digital image processing unit 10 is also accommodated in the equipment cabinet 9.
  • the video camera 5 is advantageously on an already existing above the channel 14 Bridge girders attached.
  • the supporting structure 11 also carries the lighting device 7, with which the surface 13 can be illuminated with artificial lighting at night or in difficult lighting conditions, so that uninterrupted operation of the method according to the invention is ensured.
  • the measurement of the discharge using the method according to the invention is carried out as follows.
  • the ascending air bubbles 12 generated by the compressed air supply unit 4 reach the surface 13 of the fluid.
  • the air bubbles 12 floating on the surface are detected by means of the video camera 5.
  • the video images are evaluated in the microprocessor 6 with digital image processing in the equipment cabinet 9 on site.
  • the video images can also be optionally stored digitally on mass storage or analogously on video recorders, in order to be evaluated at a later point in time in an image processing unit 12 with a microprocessor 6 and digital image processing.
  • the current rate of rise u s of the air bubbles can be determined by an intermittent operation of the compressed air supply 4 in order to determine the influence of the temperature, to take into account the density and the contents of the measuring medium.
  • the compressed air supply 4 to the bubble-generating diffusers 1 is briefly interrupted. The result is that no new air bubbles 12 form at the moment.
  • To calculate the current bubble rate u s according to Eq. (11) it is necessary to determine the period of time t 2 -t- j _ between the detachment of the last bubble before the interruption or optionally the first bubble after restarting from the bubble-generating diffusers 1 and reaching the water surface 13 as well as the water depth w.
  • Eq. (11) mean u s - the current rate of climb of the bubbles, ie the value to be determined, w - the vertical distance between the separation point on the diffuser 1 and the water surface 13 in the defined partial section of the electronic camera 5; depending on the place of use, this quantity is measured by a suitable measuring device (eg precision level, ultrasound probe, etc.), t 1 ⁇ the point in time at which the compressed air supply is interrupted or, optionally, the compressed air supply is restarted; this size is registered by the electronic evaluation unit, t 2 - the time of the appearance of the last or optionally the first bubble in a variable calibration section of the camera image; this size is determined with the aid of the digital image processing unit 10 and corresponding software. With the digital image processing unit 10, the drift of the air bubbles 12 recorded with a camera 5 can be further processed in such a way that the outflow through the flow cross section can be determined directly.
  • a suitable measuring device eg precision level, ultrasound probe, etc.
  • the light reflected at the bubble interface provides brightness information on the surface 13, over the gray value range of which the position of the air bubbles 12 is detected and the coordinates of the bubbles in the image section are determined in a computer-aided manner according to predetermined categories.
  • a complex processing sequence is required to find the air bubbles 12 in an image of the surface 13.
  • the algorithm for recognizing air bubbles 12 on surface 13 is composed primarily of filter operations.
  • the features of the image are extracted, statistically processed and evaluated. All coordinates of the detected bubbles fall within the limited value range that is determined by the image section of the camera 5. This range of values is divided into a number of constant intervals. Each interval forms a class, the class width determining the resolution of the drift. All drift measurement results (x coordinates of the bubbles) are assigned to the individual classes and the relative frequency is determined.
  • Statistical measures of the frequency distribution are the mean and the skew, since the bubbles flow through the surface 13 or through can distribute a wind-induced surface flow asymmetrically around the mean. A distinction can be made between positive and negative skewness. Since the statistical measures depend on the number of bubbles, the scattering range is reduced by overlaying several images.
  • the drift of the bubbles can now be clearly determined on the basis of the mean value and the skewness of the frequency distribution.
  • the total discharge is calculated according to Eq. (7).
  • the measurement according to the invention is possible with a high temporal resolution.
  • FIG. 7 shows a further example of application of the arrangement according to the invention or of the method according to the invention in the region of a bridge.
  • a partial cross-section is shown in which the bridge girder 15 held on a foundation 17 by means of a pillar 16 can be seen.
  • the camera 5, for example a CCD camera is arranged on the bridge support 15.
  • the channel 14 with the surface 13 and the sole 8 has a low and at the same time fluctuating flow rate.
  • Conventional measuring methods for determining the flow velocity or the outflow such as, for example, wing or float measurements, cause considerable difficulties in channels with very low flow velocities. If, for example, the discharge in a channel decreases extremely, it can happen that the mean flow velocity falls below 10 mm / s drops.
  • the discharge measurement by means of air bubbles 12 is a suitable method for determining the discharge directly and precisely.
  • the measurement was made in the flow cross section under a bridge.
  • the uniformity of the flow cross-section allowed it to be limited to the discharge measurement on the bridge pillars 16.
  • rows of the diffusers 1 according to the invention were installed in a diffuser holder 2 on the base 8, which protrude 3.0 m into the flow cross-section (FIG 7).
  • the diffuser holder 2 was fastened to the pillar 16 by means of a holding device 19.
  • the compressed air line 3 and the compressed air supply unit 4 connected to it and the digital image processing unit 10 are not shown in FIG. 7.
  • the camera 5 is connected to the digital image processing unit 10 by means of the signal derivative 18.
  • FIGS. 8 to 10 show diffusers 1, with which gas bubbles, in particular air bubbles 12 in water, can be produced absolutely uniformly with regard to their size and chronological order in order to generate gas bubbles as a measuring medium for the method according to the invention for measuring the discharge .
  • the diffuser 1 has a gas inlet 30 with an inlet opening 31 for the supply of the gas.
  • the gas exits at the gas outlet 45 with the outlet opening 46 to form gas bubbles (not shown) into the liquid.
  • the gas inlet 30 is connected to the gas outlet 45 via the gas channel 47.
  • a throttle 32 designed as a cannula 43 with a wire 44 inserted therein is arranged in the gas channel 47.
  • the diameter of the wire 44 is smaller than the diameter of the cannula 43, so that the throttle opening 33 which throttles the gas flow is formed in the space between the wire 44 and the cannula 43 and which sem case extends along the gap.
  • the opening area of the throttle opening 33 is equal to the cross-sectional area of the intermediate space.
  • the throttle 32 opens downstream in the region of the bottom 35 of the blind hole 34 into the blind hole 34 formed as a cylindrical bore.
  • the inlet point 48 at which the gas from the throttle 32 enters the blind hole 34 is not found in this example directly at the bottom 35 of the blind hole 34, since the cannula 43 protrudes somewhat into the blind hole 34. However, the inlet point 48 could also be in the bottom 35 of the blind hole 34.
  • the blind hole 34 extends from its bottom 35 towards its open end 36 in the direction of the gas outlet 45.
  • the cross section of the blind hole 34 is larger than the opening area of the throttle opening 33, so that at this point the available for the flow of the gas Cross section enlarged.
  • the last fluidic construction element of the diffuser 1 is the open end 36 of the blind hole 34, which forms the outlet opening 46 of the gas outlet 45.
  • the diffuser 1 is oriented in the liquid such that the air bubbles 12 emerge vertically upward.
  • other orientations are also conceivable, including those in which the cannula 43 and the blind hole 34 have a different angle than shown in FIG. 8 to form each other.
  • the blind hole 34 and the cannula 43 lie in a polyamide support part 41, which is designed as a hexagon screw and has a thread 42 on the outside.
  • the cannula 43 is made of stainless steel with an inside diameter of 0.115 mm and an outside diameter of 0.68 mm.
  • the wire 44 guided in it also exists made of stainless steel with a diameter of 0.10 mm and is secured to the cannula 43 by soldering against displacement.
  • the cannula 43 is 20 mm long.
  • the cannula 43 and the wire 44 guided in it protrude 2 mm into the blind hole 34, measured from the bottom 35 of the blind hole 34.
  • the length of the cannula 43 inside and outside of the carrier part 41 is 9 mm in each case.
  • the carrier part 41 designed as a hexagon screw has a total length of 24 mm, the shaft being 20 mm and the head being 4 mm long.
  • the blind hole 34 is 14 mm deep, its diameter is 2 mm.
  • the air or the gas enters the gas channel 47 of the diffuser 1 from a compressed air supply system through the gas inlet 30. Due to the operating pressure present at the gas inlet 30 and the lower external hydrostatic pressure of the liquid, a pressure difference results, due to which gas bubbles form which exit into the liquid at the gas outlet 45.
  • a modified diffuser 1 is shown in FIG. It differs from the diffuser 1 according to FIG. 8 by an additional cylindrical expansion recess 38 formed in the diffuser 1.
  • the inner end 39 and the outer end 40 of the expansion recess 38 have a diameter of 3 mm.
  • the expansion recess 38 is 4 mm long.
  • the blind hole 34 is therefore 4 mm shorter than in the diffuser 1 according to FIG. 8; the other dimensions are the same.
  • the outer end 40 of the expansion recess 38 forms the outlet opening 46.
  • FIG. 10 shows a further modified embodiment of the diffuser 1. It differs from the diffuser according to FIG. 8 in that it is additionally formed in the diffuser 1. dete, conical expansion recess 38.
  • the conical expansion recess 38 has a diameter of 3 mm at the outer end 40 and a diameter of 2 mm at the inner end 39, which corresponds to the diameter of the blind hole 34.
  • the conical expansion recess 38 is 1 mm long.
  • the blind hole 34 is thereby shortened by 1 mm compared to the embodiment in FIG. 8; the other dimensions correspond to those of the diffuser 1 according to FIG. 8.
  • the outer end 40 of the expansion recess 38 forms the outlet opening 46.

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Abstract

L'invention concerne un procédé permettant de déterminer l'écoulement d'un liquide à surface libre dans une rigole, à l'aide de bulles de gaz servant de moyen de mesure, ainsi qu'un agencement et un dispositif pour la mise en ÷uvre dudit procédé. Ce procédé et cet agencement permettent de mesurer directement de manière extrêmement fiable et sans pertes des écoulements, notamment dans le cas de faibles débits. A cet effet, une suite de bulles de gaz individuelles est produite, dans le temps, au moyen de diffuseurs (1) répartis, dans l'espace, au-dessus d'une zone de coupe transversale du fond (8) de la rigole (14). Les bulles de gaz ont une dimension qui leur permet de progresser du fond (8) de la rigole (14) jusqu'à la surface supérieure (13) de ladite rigole (14), à une vitesse ascensionnelle (us) à peu près constante. Il est opéré au moins une prise de vue de la dérive horizontale des bulles de gaz à la surface (13) de la rigole (14) à l'aide d'au moins un appareil optique de prise de vues, disposé en dehors du liquide. L'image obtenue est évaluée au moyen d'une unité de traitement de l'image, afin de déterminer l'écoulement de la rigole.
PCT/DE1994/000445 1993-04-22 1994-04-20 Procede, agencement et dispositif permettant de determiner l'ecoulement d'un liquide a surface libre WO1994024522A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DEP4313682.6 1993-04-22
DE19934313681 DE4313681C1 (de) 1993-04-22 1993-04-22 Diffusor zur Erzeugung definierter Luftblasen als Meßmedium und Verfahren zur Messung der Fließgeschwindigkeit in langsam und mit freiem Spiegel fließenden Flüssigkeiten
DEP4313681.8 1993-04-22
DE4313682A DE4313682C2 (de) 1993-04-22 1993-04-22 Verfahren zur visuellen Bestimmung und Messung des Abflusses von langsam und mit freiem Spiegel fließenden Flüssigkeiten unter Verwendung von Luftblasen als Meßmedium und eine Anordnung zur Durchführung des Verfahrens

Publications (1)

Publication Number Publication Date
WO1994024522A1 true WO1994024522A1 (fr) 1994-10-27

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PCT/DE1994/000445 WO1994024522A1 (fr) 1993-04-22 1994-04-20 Procede, agencement et dispositif permettant de determiner l'ecoulement d'un liquide a surface libre

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WO (1) WO1994024522A1 (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2317072A1 (fr) * 2009-10-30 2011-05-04 Welltec A/S Outil de journalisation de bulles
CN104820112A (zh) * 2015-04-24 2015-08-05 华南理工大学 一种植物叶脉流速测量的装置及方法
CN106918717A (zh) * 2017-03-22 2017-07-04 北京尚水信息技术股份有限公司 利用所拍摄的图像对两相流流场进行处理的方法
EP3252435A1 (fr) * 2016-06-01 2017-12-06 Perwatec UG (haftungsbeschränkt) Procédé de mesure de débit dans des canaux
CN112147365A (zh) * 2020-09-30 2020-12-29 中国水利水电科学研究院 一种基于深度学习的河道流速视频监测装置及方法
CN113720401A (zh) * 2021-09-27 2021-11-30 成都市环境应急指挥保障中心 一种基于水下粒子测速的明渠流量测量系统和方法

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1045115B (de) * 1955-03-23 1958-11-27 Joachim Thon Dipl Ing Verfahren und Einrichtung zur Abflussmessung in offenen Gerinnen

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1045115B (de) * 1955-03-23 1958-11-27 Joachim Thon Dipl Ing Verfahren und Einrichtung zur Abflussmessung in offenen Gerinnen

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2317072A1 (fr) * 2009-10-30 2011-05-04 Welltec A/S Outil de journalisation de bulles
CN104820112A (zh) * 2015-04-24 2015-08-05 华南理工大学 一种植物叶脉流速测量的装置及方法
CN104820112B (zh) * 2015-04-24 2018-01-05 华南理工大学 一种植物叶脉流速测量的装置及方法
EP3252435A1 (fr) * 2016-06-01 2017-12-06 Perwatec UG (haftungsbeschränkt) Procédé de mesure de débit dans des canaux
CN106918717A (zh) * 2017-03-22 2017-07-04 北京尚水信息技术股份有限公司 利用所拍摄的图像对两相流流场进行处理的方法
CN112147365A (zh) * 2020-09-30 2020-12-29 中国水利水电科学研究院 一种基于深度学习的河道流速视频监测装置及方法
CN113720401A (zh) * 2021-09-27 2021-11-30 成都市环境应急指挥保障中心 一种基于水下粒子测速的明渠流量测量系统和方法

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