CA1093676A - Liquid flow rate metering system - Google Patents
Liquid flow rate metering systemInfo
- Publication number
- CA1093676A CA1093676A CA276,721A CA276721A CA1093676A CA 1093676 A CA1093676 A CA 1093676A CA 276721 A CA276721 A CA 276721A CA 1093676 A CA1093676 A CA 1093676A
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- flow rate
- craft
- speed
- acoustic
- liquid
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Abstract
ABSTRACT OF THE DISCLOSURE:
The invention relates to a liquid flow rate metering system on board of a moving craft providing results corrected for faults due to the craft movement. A flow rate meter is provided for measurement of longitudinal and of trans-verse components of liquid flow rate by reference to the craft, whereas a speedometer system determines longitudinal and trans-verse components of the craft speed with respect to the supporting liquid bottom. An output data processor derives from the flow rate and the speed measured values a value of longitudinal and of transverse components of the flow rate at relative layer distributions with respect to the bottom.
Preferably, a sonar and a flow rate meter use a single acoustic unit in a shared-time operation controlled by a master clock. Application in the determination of the speed and direction of movement of a body of fluid.
The invention relates to a liquid flow rate metering system on board of a moving craft providing results corrected for faults due to the craft movement. A flow rate meter is provided for measurement of longitudinal and of trans-verse components of liquid flow rate by reference to the craft, whereas a speedometer system determines longitudinal and trans-verse components of the craft speed with respect to the supporting liquid bottom. An output data processor derives from the flow rate and the speed measured values a value of longitudinal and of transverse components of the flow rate at relative layer distributions with respect to the bottom.
Preferably, a sonar and a flow rate meter use a single acoustic unit in a shared-time operation controlled by a master clock. Application in the determination of the speed and direction of movement of a body of fluid.
Description
~ rhe present invention relates to a system for determining a flu~d flo~ rate. It relates more particularly to a measurement system which enables the determination of the speed and direction of movc~nen-t of a body o-~ fluid, ;uch .a a cu~rent which exists 5 within a liquid, the Doppler effect being used for carrying out the measurements from a moving craft.
; It should be pointed out that it has become necessary to discover the characteristics of the currents which exist in liquid layers at different depths in shallow waters, in particular for 10 the purposes of exploiting the underwater bed and/or ground under the bed.
An invention in the prior art, disclosed in U.S.
patent N 3,~35,677, relates to a system for measuring the direc-tion and velocity of currents in a liquid medium by comparing 15 changes in f~equency of signals between sensors which are selec-tively spaced apart and submerged in the medium.
Another electronic me~suring system based on Doppler effect and which forms a flow rate meter is known, inter alia, from a French patent filed by the present Applicant under 20 M 72 03320 and published as N 2,170,80'7. This system provides the two relative components of the flow rate of water layers with respect to the craft and, by subtracting the vector for speed with respect to the underwater bed, makes it possible to deduce the speed of the fluid current in magnitude, direction 25 and distribution Further, namely in an U.S. patent N 3,818,425, filed by the present Applicant, there is described a navigation system which employs the Doppler effect and which enable~ the two 1()93676 longitudinal and transverse components o-f the speed of the craft to be obtained with respect to the sea bottom.
This Doppler sonar navigation system comprises an on--board acoustic waves transmit and recelve electro-acoustic trans-ducers device ; transmission and reception take place in a mannerknown per se in four directions with beams equally inclined in respect to the vertical and located in two mutually perpendicular planes, the receiving electro-acoustic transducer elements being located upon the focal sphere of a spherical acoustic lens. The assembly is enclosed within a casing filled with a fluid medium having a known ultrasonic wave propagation velocity dependent on the fluid temperature, the latter being controllable. ~he trans-ducers are directed towards the casing base which is transparent to the ultrasonic waves. The casing is secured to the vessel hull and said base is in contact with supporting water.
However, neither of these systems used separately does ~ot provide the possibility of determining the speed characte-ristics with respect to the sea bottom of a current existing within a body of liquid, without using either fixed immersed apparatus or requiring that the measurements be carried out only when the craft carrying the measuring equipment is motionless.
It is one object of the present invention to provide a possibility to determine correctly the flow rate of liquid layers at different depths.
Such a problem arises when it is sought to know the flow rate ~ with respect to the liquid bottom, i.e. within determined reference marks, of a sea current when a flow rate metering system is on-board of a craft moving with a speed V1 1~936716 by reference to sea bottom, this speed causing disturbance in the flow rate measure; this disturbance appears in an equation:
_~ 2 Vl where V2 is the sea current, as related to the craft and which is provided by the flow rate meter on-board.
If the reference axes are ! a ~-X axis following the craft forward movement which is in the same direction as the X axis of the flow rate meter, and a O-Y axis perpendicular to OX axis in a horizontal plane, the sought true flow rate ~ will be derived by its two horizontal components Vl and V2 from two equations:
Vl ~ V21 Vll and V2 ~ V22 V12 which relate respectively to the longitudinal and to the trans-versal projections of three respective vectors V, V2 and Vl.
Another object of the invention is to provide an improved flow rate system,the operation of which is advanta-geously implemented for example by means of the two above mentioned prior art systems disclosed by the Applicant, the systems being combi.ned to cooperate through a switching means, a common electro-acoustic transducers unit and an output data processor, wherein the determination of currents in liquid layers is possible from a moving craft having the entire system on-board.
Such.measurements of currents within a liquid are of prime importance, particularly in cases where the underwater bed is to be prospected, build on and exploited, for example in the case of undersea drilling.
According to the invention there is provided a liquid flow rate metering system on board of a moving craft providing results corrected for faults due to the craft movement comprising in a cooperating combination;
,:
- a flow rate meter for measurement of longitudinal and of transverse components of liquid flow rate by reference to the craft;
- a speedometer system for determining longitudinal and trans-verse components of the craft speed with respect to the supporting liquid bottom; and - an output data processor for deriving from the flow rate and the speed measured values a value of longitudinal and of trans-verse components of the flow rate at relative layer distribution with respect to said bottom.
Otherfeatures and advantages of the invention will become apparent from the following description, given by way of example, with reference to the appended drawings in which:
- Fig. 1 is a diagram representing vectors for different speeds and essentially intended to facilitate a better understanding of the invention;
- Fig. 2 is a synoptic diagram in blocks form of the basic of the flow rate metering system in accordance with the invention;
- Fig. 3 is a synoptic schematically illustrating a prior art flow rate system, - Pig. 4 is a block diag~am of an on-board flow rate metering system according to the invention;
- Fig. 5 is a synoptic schematically illustrating a prior art electro-acoustic transducers unit in a Doppler sonar navigation system implemented for determining the components of speed of the craft; and Fig. 6 a diagram of operation versus time of the metering system.
~riefly stated, the system proposed uses the synoptic block diagram of Fig., 2 as the basic of the flow rate metering system. The system essentially comprises means in a _ 5 _ ' 1(~93676 cooperating combination and advantageously of conventional embodiments:
- a flow rate meter 3, which measures sea current components V
5a -~j and V22 with respect to the craft, - a craft speedometer 1, which measures the craft components Vll and V12 by reference to fixed axes, and - a subtractor circuit 7 carrying out arithmetic calculu~ which gives the differences between V21 - Vll and V22 - V12.
It is worth to note that the proposed system is operable by combining any known system as meter 3, if it provides the two horizontal components of the sea current flow rate with respect to the craft, with any known system as speedometer 1 if this latter provides the two horizontal components of the craft speed with respect to fixed reference marks.
When data of measured values Vll, V12 and V21~ V22 is continuously provided, the substractor circuit 7 is a simple analogical subtraction circuit and the two sought datas Vl and V2 are also continuously provided.
As previously stated, the system embodiment advanta-geously utilises known per se equipment and namely in a preferred arrangement, the measuring systems disclosed in previously Gited French patent No 2,170,807 and in U.S. patent No 3,818,425. The system comprises, FIG. 4, a sonar apparatus 1 used as craft speedometer and a sea current metering apparatus, or flow rate meter 3, which are each divided into a transmission section and a reception section, which latter feeds an output data-processing device 6.
In said French patent No 2,170,807, synoptically illustrated in FIG. 3, is described a flow rate device based on Doppler effect produced by volume reverberation, i.e. by the signal returned by the medium heterogeneities. In this device four electro-acoustic transducers are inclined in respect to the vertical axis and mounted in two mutually perpendicular planes ;
the received signals from transducers are processed to provide the two horiz~ntal components of the current speed of a water 10~367S
layer lying below said device.
On the other hand, in said U.S. patent No 3,818,425, synoptically illustrated in FI~.5, is described the craft speedometer by reference to the sea bottom which is also based on the Doppler effect of the signal reflected from the bottom.
This device utilizes four electro-acoustic transducers inclined in respect to the vertical axis, as in the above cited French patent, but mounted within a container transparent for ultrasonic waves and filled with a fluid medium the physical properties of which make the velocity of ultrasonic waves propagation dependant on the medium temperature which is stabilized at a selected value adjustable by a temperature control means.
Returning now to the system arrangement, the latter further comprises a controlled switch means 2 advantageously embodied by any convenient conventional logic circuit. ~he switch terminals are connected to the corresponding terminals of sonar 1 and flow rate meter 3; the connections lines on the drawing have an arrow oriented towards switch 2 to indicate the transmission period of operation and an oppositely oriented arrow indicates the reception period.
Another terminal of switch 2 is connected to an acoustic unit 5, as indicated by a connection which carries arrows symbolising transmission or reception depending upon their direction. This unit is advantageously formed by a set of electro-acoustic transducers for reception which are arranged within a liquid lens and by a set of emitting transducers, these two sets being arranged within a sealed container filled with a liquid. The velocity of propagation in the liquids employed depends on the temperature of the liquids which is regulated and adjustable. Such an arrangement is described in the aforementioned U.S. patent No 3,818,425.
In addition, a master timer or clock 4 is connected 10~3676 to the sonar 1, the switch 2 and the flow rate meter 3. This arrangement makes it possible to use the same clock to control the system operation as a transmitter and as a receiver of each of the pieces of equipment which are connected sequentially to the transducers unit 5 by the switch 2, whose switching cycle is slaved to the predetermined period To of the clock signal.
Thus, using a switcheable common transmit-receive unit it is possible to provide a relative flow rate measurement since not corrected in respect to the craft own speed, and an accurate craft speed as obtained from Doppler sonar ; as is apparent to those skilled in the art, the true flow rate characteristics of the liquid is then derived by subtracting from the measured flow rate components the determined craft speed components, the calcu-lation being carried in any convenient subtraction circuit provided in above mentioned data processing device 6.
A preferred embodiment of the system has the following characteristics :
- operating frequency : 300 kHz, - range for measuring the craft speed over the bottom : approxi-.
10~3676 mately 150m,- range for measuring the liquid flow rate : approximately lO0 m, - numbcr of flow rate measuring points : ~2, i.e. one measurement every 3 meters of layers dephts difference ;
- accuracy of measurement : 1 ~ with a limit of approximately l/100 knot.
An example of a complete cycle of operations briefly comprises :
- the system being activated and the flow rate meter ~ being connccted through the switch 2, as shown, to the transducers unit 5, the transmitting transducers excited by signals from the flow rate metering system radiate acoustic energy in the liquid medium ;
the receiving transducers receive the energy reflected from 1'j p1rticlcs in the liquid layers which is transferred to processing circuits of the flowmeter where the flow rate is computed, this operation being carried in convent-.onal manner during a prede-termined cycle with a duration To at least equal to the largest :-transmission-reception time.
At the end of this cycle To, the control signal from the master clock 4 activates the sonar system 1 which is simulta-neously co~mected through switch 2 to the transducers unit 5 just previously disconnected, acoustic energy is radiated, reflected, received and then processed and computed to derive the speed of the craft, the conventional operation being carrier during a cycle of the same duration To.
The successive operations alternating sequentially, the obtained values of flow rate and craft speed are processed in any _ g _ ~
convenient conventional subtracting means for deriving the sought liquid flow rate values, said subtractor circuit being a part of an output data processor 6.
A complete preferred embodiment will be described now by reference to the drawings FIG. 4 in which one single electro-acoustic transducers unit 5 commonly used for both cooperating systems 1 and 3.
The already above mentioned unit, FIG. 5, comprises an assembly of four transmit and four receive transducers operating alternately for transmission and for reception and mounted within a housing filled with a fluid, such as conven-tionally used castor or silicone oil, the temperature of which is controlled, thus correcting the measurements made in accordance with the velocity c2 of the sea medium at the moment of these measurements.
Each of the unit 5 transducers is sequentially switched on one and then on the other of the two systems 1 and 3 by means of the controlled switch 3. A clock 4, the period of which determines the complete cycle of the measurement, controls the switch 2 and the respective half cycles of measurement of each system 1 and 3. The dur~tion of a complete cycle is aboùt 0.5 seconds and of each half cycle about 0.25 seconds. During each half cycle the systems 1 and 3 determine the respective components ~ . ~.
of speeds Vl and V2 which, applied in the output data processor 6 to the subtraction circuit 7, produce the components of the sought speed V. A conventional sampling circuit 8, controlled by the clock 4 signal, provides during each complete cycle of operation the flow rate measuring points of 32 pairs of values of V sample each 4 ms, i.e. within fluid layers thickness of about 3 meters.
10~3676 ~ he clock 4, h~ving a period T o~ about 0.5 seconds, is connected to -the switch 2, to the flow rate me-ter 3 and to the sonar system used as craft speedometer 1. The complete cycle of 0.5 sccondv is divided in two half cycles, each of about 0.25 seconds in duration.
At the beginning of a cycle, the clock 4 controls different circuits operation and connects, through the switch 2, the four transducers of the unit 5 to the corresponding terminals of the flow rate meter 3 and simultaneously actuates its transmit-receive cycle of operation. The diagrams of operation versus time are illustrated on ~IG. 6, and clearly show the successive operations during this half cycle.
This half cycle -operations begin by transmitting a short 300 k~z frequency signal of a high level since the returned ener~y by heterogeneities of the medium, and which is used for the measurement, is of a very low level. During this transmission, -four receiving amplifiers comprised in syst~m 3 are inoperative and remain in this state about 5 ms after the end of the trans-mitted signal. A window for flow rate measurement is then made avai]~ble for a period of 128 ms during which the receiving amplifiers present their full sensitivity. During these 128 ms the four return signals received are processed in a known per se way to determine, with respect to the craft, the longitudinal component V51 and the transversal component V52 of the flow rate of the sea current such as exists at the vertical of the craft.
~ he ~mplifiers are then off operation till the end of the complete cycle. ~hus, they do not receive the bottom return signal when, in the most encountered cases, this signal arrives after opera-tion time o-f the reception ~/indo~J of the flow rate meter 3.
At the beginning o~ the second half cycle, the clock si~nrll connects, t~ough the switch 2, the four transducers of unit 5 to the corresponding terminals of sonar system 1 used for craft speedometer. This cycle operation begins by transmitting a short 300 ~z frequency signal of a low level since the returned energy by the bottom is 40 to 60 d~ higher than the one returned by the heterogeneities of the sea medium. During this transmission, the fou~ receiving amplificrs of system 1 are inoperative and remain in this state about 9 ms after the end of tr~lsmitted signal. A window for craft speed measurement is then made available for a period of 200 ms during which the four receiving amplifiers present their full sensitivity. I~lhen, at ~ly momen-t within this 200 ms period, the energy returned by the bottom is received, the four signals are processed in a kno~n per se manner and are detected with a sufficient time constant to get D.C. voltages V41 and V42 respectively corresponding to longitudinal and tra-nsversal crait speed components in respect to the sea bottom.
~he output terminals of systems 1 and 3 are connected to respective input terminals of the subtractor circuit 7 of signal pair V51 and V41 on one hand, and V52 and V42 on the other h~d.
The output data processor 6 further comprises a sampler 8 which operates on substractor 7 output signals. During the 128 ms period of operation of the reception window of system 3, this sampler is utilised for 32 measuring points, in other ~Jords `` :10~3676 32 successive samplings are made, each during 4 ms, and are then sorted in 32 separate output pairs V0ll and V012' -- ' V321 n V322. For this purpose, the clock 4 signal is applied to the sampler 8 and, during the operation of the measurement window of the first half cycle, successively controls the state of its 32 gates, each for a period of 4 ms, thereby successively connecting the signal pair Vl and V2 to the respective outputs VO11 and V0l2, ,.. , V321 and V322 The flow rate meter signal issued from 3, corrected by subtraction in 7 of the craft speedometer signal issued from system 1, appears then at the output terminals of the sampler 8 on 32 separate channels, each channel comprising data on current speed in a water layer, the thickness of which is about three meters account being made of the sound velocity in water and of the windows duration.
Thus, the preferred example of embodiment of the proposed metering system can easily provide water currents measurements through a total liquid depth of about 96 meters.
A system embodiment, operated in accordance with the teaching of the invention, makes it possible to determine the characteristics of flow rate in liquid layers without using immersed apparatus and with the carrier craft moving. This represents a considerable technical advance in the so-called off-shore field, where such measurements are of fundamental importance.
; It should be pointed out that it has become necessary to discover the characteristics of the currents which exist in liquid layers at different depths in shallow waters, in particular for 10 the purposes of exploiting the underwater bed and/or ground under the bed.
An invention in the prior art, disclosed in U.S.
patent N 3,~35,677, relates to a system for measuring the direc-tion and velocity of currents in a liquid medium by comparing 15 changes in f~equency of signals between sensors which are selec-tively spaced apart and submerged in the medium.
Another electronic me~suring system based on Doppler effect and which forms a flow rate meter is known, inter alia, from a French patent filed by the present Applicant under 20 M 72 03320 and published as N 2,170,80'7. This system provides the two relative components of the flow rate of water layers with respect to the craft and, by subtracting the vector for speed with respect to the underwater bed, makes it possible to deduce the speed of the fluid current in magnitude, direction 25 and distribution Further, namely in an U.S. patent N 3,818,425, filed by the present Applicant, there is described a navigation system which employs the Doppler effect and which enable~ the two 1()93676 longitudinal and transverse components o-f the speed of the craft to be obtained with respect to the sea bottom.
This Doppler sonar navigation system comprises an on--board acoustic waves transmit and recelve electro-acoustic trans-ducers device ; transmission and reception take place in a mannerknown per se in four directions with beams equally inclined in respect to the vertical and located in two mutually perpendicular planes, the receiving electro-acoustic transducer elements being located upon the focal sphere of a spherical acoustic lens. The assembly is enclosed within a casing filled with a fluid medium having a known ultrasonic wave propagation velocity dependent on the fluid temperature, the latter being controllable. ~he trans-ducers are directed towards the casing base which is transparent to the ultrasonic waves. The casing is secured to the vessel hull and said base is in contact with supporting water.
However, neither of these systems used separately does ~ot provide the possibility of determining the speed characte-ristics with respect to the sea bottom of a current existing within a body of liquid, without using either fixed immersed apparatus or requiring that the measurements be carried out only when the craft carrying the measuring equipment is motionless.
It is one object of the present invention to provide a possibility to determine correctly the flow rate of liquid layers at different depths.
Such a problem arises when it is sought to know the flow rate ~ with respect to the liquid bottom, i.e. within determined reference marks, of a sea current when a flow rate metering system is on-board of a craft moving with a speed V1 1~936716 by reference to sea bottom, this speed causing disturbance in the flow rate measure; this disturbance appears in an equation:
_~ 2 Vl where V2 is the sea current, as related to the craft and which is provided by the flow rate meter on-board.
If the reference axes are ! a ~-X axis following the craft forward movement which is in the same direction as the X axis of the flow rate meter, and a O-Y axis perpendicular to OX axis in a horizontal plane, the sought true flow rate ~ will be derived by its two horizontal components Vl and V2 from two equations:
Vl ~ V21 Vll and V2 ~ V22 V12 which relate respectively to the longitudinal and to the trans-versal projections of three respective vectors V, V2 and Vl.
Another object of the invention is to provide an improved flow rate system,the operation of which is advanta-geously implemented for example by means of the two above mentioned prior art systems disclosed by the Applicant, the systems being combi.ned to cooperate through a switching means, a common electro-acoustic transducers unit and an output data processor, wherein the determination of currents in liquid layers is possible from a moving craft having the entire system on-board.
Such.measurements of currents within a liquid are of prime importance, particularly in cases where the underwater bed is to be prospected, build on and exploited, for example in the case of undersea drilling.
According to the invention there is provided a liquid flow rate metering system on board of a moving craft providing results corrected for faults due to the craft movement comprising in a cooperating combination;
,:
- a flow rate meter for measurement of longitudinal and of transverse components of liquid flow rate by reference to the craft;
- a speedometer system for determining longitudinal and trans-verse components of the craft speed with respect to the supporting liquid bottom; and - an output data processor for deriving from the flow rate and the speed measured values a value of longitudinal and of trans-verse components of the flow rate at relative layer distribution with respect to said bottom.
Otherfeatures and advantages of the invention will become apparent from the following description, given by way of example, with reference to the appended drawings in which:
- Fig. 1 is a diagram representing vectors for different speeds and essentially intended to facilitate a better understanding of the invention;
- Fig. 2 is a synoptic diagram in blocks form of the basic of the flow rate metering system in accordance with the invention;
- Fig. 3 is a synoptic schematically illustrating a prior art flow rate system, - Pig. 4 is a block diag~am of an on-board flow rate metering system according to the invention;
- Fig. 5 is a synoptic schematically illustrating a prior art electro-acoustic transducers unit in a Doppler sonar navigation system implemented for determining the components of speed of the craft; and Fig. 6 a diagram of operation versus time of the metering system.
~riefly stated, the system proposed uses the synoptic block diagram of Fig., 2 as the basic of the flow rate metering system. The system essentially comprises means in a _ 5 _ ' 1(~93676 cooperating combination and advantageously of conventional embodiments:
- a flow rate meter 3, which measures sea current components V
5a -~j and V22 with respect to the craft, - a craft speedometer 1, which measures the craft components Vll and V12 by reference to fixed axes, and - a subtractor circuit 7 carrying out arithmetic calculu~ which gives the differences between V21 - Vll and V22 - V12.
It is worth to note that the proposed system is operable by combining any known system as meter 3, if it provides the two horizontal components of the sea current flow rate with respect to the craft, with any known system as speedometer 1 if this latter provides the two horizontal components of the craft speed with respect to fixed reference marks.
When data of measured values Vll, V12 and V21~ V22 is continuously provided, the substractor circuit 7 is a simple analogical subtraction circuit and the two sought datas Vl and V2 are also continuously provided.
As previously stated, the system embodiment advanta-geously utilises known per se equipment and namely in a preferred arrangement, the measuring systems disclosed in previously Gited French patent No 2,170,807 and in U.S. patent No 3,818,425. The system comprises, FIG. 4, a sonar apparatus 1 used as craft speedometer and a sea current metering apparatus, or flow rate meter 3, which are each divided into a transmission section and a reception section, which latter feeds an output data-processing device 6.
In said French patent No 2,170,807, synoptically illustrated in FIG. 3, is described a flow rate device based on Doppler effect produced by volume reverberation, i.e. by the signal returned by the medium heterogeneities. In this device four electro-acoustic transducers are inclined in respect to the vertical axis and mounted in two mutually perpendicular planes ;
the received signals from transducers are processed to provide the two horiz~ntal components of the current speed of a water 10~367S
layer lying below said device.
On the other hand, in said U.S. patent No 3,818,425, synoptically illustrated in FI~.5, is described the craft speedometer by reference to the sea bottom which is also based on the Doppler effect of the signal reflected from the bottom.
This device utilizes four electro-acoustic transducers inclined in respect to the vertical axis, as in the above cited French patent, but mounted within a container transparent for ultrasonic waves and filled with a fluid medium the physical properties of which make the velocity of ultrasonic waves propagation dependant on the medium temperature which is stabilized at a selected value adjustable by a temperature control means.
Returning now to the system arrangement, the latter further comprises a controlled switch means 2 advantageously embodied by any convenient conventional logic circuit. ~he switch terminals are connected to the corresponding terminals of sonar 1 and flow rate meter 3; the connections lines on the drawing have an arrow oriented towards switch 2 to indicate the transmission period of operation and an oppositely oriented arrow indicates the reception period.
Another terminal of switch 2 is connected to an acoustic unit 5, as indicated by a connection which carries arrows symbolising transmission or reception depending upon their direction. This unit is advantageously formed by a set of electro-acoustic transducers for reception which are arranged within a liquid lens and by a set of emitting transducers, these two sets being arranged within a sealed container filled with a liquid. The velocity of propagation in the liquids employed depends on the temperature of the liquids which is regulated and adjustable. Such an arrangement is described in the aforementioned U.S. patent No 3,818,425.
In addition, a master timer or clock 4 is connected 10~3676 to the sonar 1, the switch 2 and the flow rate meter 3. This arrangement makes it possible to use the same clock to control the system operation as a transmitter and as a receiver of each of the pieces of equipment which are connected sequentially to the transducers unit 5 by the switch 2, whose switching cycle is slaved to the predetermined period To of the clock signal.
Thus, using a switcheable common transmit-receive unit it is possible to provide a relative flow rate measurement since not corrected in respect to the craft own speed, and an accurate craft speed as obtained from Doppler sonar ; as is apparent to those skilled in the art, the true flow rate characteristics of the liquid is then derived by subtracting from the measured flow rate components the determined craft speed components, the calcu-lation being carried in any convenient subtraction circuit provided in above mentioned data processing device 6.
A preferred embodiment of the system has the following characteristics :
- operating frequency : 300 kHz, - range for measuring the craft speed over the bottom : approxi-.
10~3676 mately 150m,- range for measuring the liquid flow rate : approximately lO0 m, - numbcr of flow rate measuring points : ~2, i.e. one measurement every 3 meters of layers dephts difference ;
- accuracy of measurement : 1 ~ with a limit of approximately l/100 knot.
An example of a complete cycle of operations briefly comprises :
- the system being activated and the flow rate meter ~ being connccted through the switch 2, as shown, to the transducers unit 5, the transmitting transducers excited by signals from the flow rate metering system radiate acoustic energy in the liquid medium ;
the receiving transducers receive the energy reflected from 1'j p1rticlcs in the liquid layers which is transferred to processing circuits of the flowmeter where the flow rate is computed, this operation being carried in convent-.onal manner during a prede-termined cycle with a duration To at least equal to the largest :-transmission-reception time.
At the end of this cycle To, the control signal from the master clock 4 activates the sonar system 1 which is simulta-neously co~mected through switch 2 to the transducers unit 5 just previously disconnected, acoustic energy is radiated, reflected, received and then processed and computed to derive the speed of the craft, the conventional operation being carrier during a cycle of the same duration To.
The successive operations alternating sequentially, the obtained values of flow rate and craft speed are processed in any _ g _ ~
convenient conventional subtracting means for deriving the sought liquid flow rate values, said subtractor circuit being a part of an output data processor 6.
A complete preferred embodiment will be described now by reference to the drawings FIG. 4 in which one single electro-acoustic transducers unit 5 commonly used for both cooperating systems 1 and 3.
The already above mentioned unit, FIG. 5, comprises an assembly of four transmit and four receive transducers operating alternately for transmission and for reception and mounted within a housing filled with a fluid, such as conven-tionally used castor or silicone oil, the temperature of which is controlled, thus correcting the measurements made in accordance with the velocity c2 of the sea medium at the moment of these measurements.
Each of the unit 5 transducers is sequentially switched on one and then on the other of the two systems 1 and 3 by means of the controlled switch 3. A clock 4, the period of which determines the complete cycle of the measurement, controls the switch 2 and the respective half cycles of measurement of each system 1 and 3. The dur~tion of a complete cycle is aboùt 0.5 seconds and of each half cycle about 0.25 seconds. During each half cycle the systems 1 and 3 determine the respective components ~ . ~.
of speeds Vl and V2 which, applied in the output data processor 6 to the subtraction circuit 7, produce the components of the sought speed V. A conventional sampling circuit 8, controlled by the clock 4 signal, provides during each complete cycle of operation the flow rate measuring points of 32 pairs of values of V sample each 4 ms, i.e. within fluid layers thickness of about 3 meters.
10~3676 ~ he clock 4, h~ving a period T o~ about 0.5 seconds, is connected to -the switch 2, to the flow rate me-ter 3 and to the sonar system used as craft speedometer 1. The complete cycle of 0.5 sccondv is divided in two half cycles, each of about 0.25 seconds in duration.
At the beginning of a cycle, the clock 4 controls different circuits operation and connects, through the switch 2, the four transducers of the unit 5 to the corresponding terminals of the flow rate meter 3 and simultaneously actuates its transmit-receive cycle of operation. The diagrams of operation versus time are illustrated on ~IG. 6, and clearly show the successive operations during this half cycle.
This half cycle -operations begin by transmitting a short 300 k~z frequency signal of a high level since the returned ener~y by heterogeneities of the medium, and which is used for the measurement, is of a very low level. During this transmission, -four receiving amplifiers comprised in syst~m 3 are inoperative and remain in this state about 5 ms after the end of the trans-mitted signal. A window for flow rate measurement is then made avai]~ble for a period of 128 ms during which the receiving amplifiers present their full sensitivity. During these 128 ms the four return signals received are processed in a known per se way to determine, with respect to the craft, the longitudinal component V51 and the transversal component V52 of the flow rate of the sea current such as exists at the vertical of the craft.
~ he ~mplifiers are then off operation till the end of the complete cycle. ~hus, they do not receive the bottom return signal when, in the most encountered cases, this signal arrives after opera-tion time o-f the reception ~/indo~J of the flow rate meter 3.
At the beginning o~ the second half cycle, the clock si~nrll connects, t~ough the switch 2, the four transducers of unit 5 to the corresponding terminals of sonar system 1 used for craft speedometer. This cycle operation begins by transmitting a short 300 ~z frequency signal of a low level since the returned energy by the bottom is 40 to 60 d~ higher than the one returned by the heterogeneities of the sea medium. During this transmission, the fou~ receiving amplificrs of system 1 are inoperative and remain in this state about 9 ms after the end of tr~lsmitted signal. A window for craft speed measurement is then made available for a period of 200 ms during which the four receiving amplifiers present their full sensitivity. I~lhen, at ~ly momen-t within this 200 ms period, the energy returned by the bottom is received, the four signals are processed in a kno~n per se manner and are detected with a sufficient time constant to get D.C. voltages V41 and V42 respectively corresponding to longitudinal and tra-nsversal crait speed components in respect to the sea bottom.
~he output terminals of systems 1 and 3 are connected to respective input terminals of the subtractor circuit 7 of signal pair V51 and V41 on one hand, and V52 and V42 on the other h~d.
The output data processor 6 further comprises a sampler 8 which operates on substractor 7 output signals. During the 128 ms period of operation of the reception window of system 3, this sampler is utilised for 32 measuring points, in other ~Jords `` :10~3676 32 successive samplings are made, each during 4 ms, and are then sorted in 32 separate output pairs V0ll and V012' -- ' V321 n V322. For this purpose, the clock 4 signal is applied to the sampler 8 and, during the operation of the measurement window of the first half cycle, successively controls the state of its 32 gates, each for a period of 4 ms, thereby successively connecting the signal pair Vl and V2 to the respective outputs VO11 and V0l2, ,.. , V321 and V322 The flow rate meter signal issued from 3, corrected by subtraction in 7 of the craft speedometer signal issued from system 1, appears then at the output terminals of the sampler 8 on 32 separate channels, each channel comprising data on current speed in a water layer, the thickness of which is about three meters account being made of the sound velocity in water and of the windows duration.
Thus, the preferred example of embodiment of the proposed metering system can easily provide water currents measurements through a total liquid depth of about 96 meters.
A system embodiment, operated in accordance with the teaching of the invention, makes it possible to determine the characteristics of flow rate in liquid layers without using immersed apparatus and with the carrier craft moving. This represents a considerable technical advance in the so-called off-shore field, where such measurements are of fundamental importance.
Claims (9)
1. A liquid flow rate metering system on board of a moving craft providing results corrected for faults due to the craft movement comprising in a cooperating combination:
- a flow rate meter for measurement of longitudinal and of transverse components of liquid flow rate by reference to the craft;
- a speedometer system for determining longitudinal and trans-verse components of the craft speed with respect to the support-ing liquid bottom; and - an output data processor for deriving from the flow rate and the speed measured values a value of longitudinal and of trans-verse components of the flow rate at relative layer distributions with respect to said bottom.
- a flow rate meter for measurement of longitudinal and of transverse components of liquid flow rate by reference to the craft;
- a speedometer system for determining longitudinal and trans-verse components of the craft speed with respect to the support-ing liquid bottom; and - an output data processor for deriving from the flow rate and the speed measured values a value of longitudinal and of trans-verse components of the flow rate at relative layer distributions with respect to said bottom.
2. System in accordance with claim 1, wherein the said output data processor comprises a subtraction circuit for determining the difference between the flow rate value and the speed value of the craft.
3. System according to claim 1, wherein the flow rate meter is an electro-acoustic flow rate meter based on the Doppler effect on volume reverberation and the speedometer is an electro-acoustic system based on Doppler effect on reverbe-ration on the sea bottom.
4. System according to claim 3, wherein the operating ultrasonic wave frequency is the same for both cooperating systems and wherein a single electro-acoustic transducers unit for transmission and for reception is sequentially connected to the terminals of the one, then of the other system through a switch controlled by a clock.
5. System according to claim 4, wherein the transducers unit is enclosed in a liquid medium filled housing, said medium having a given sound propagation velocity and having a controlled adjustable temperature for correcting measurement errors introduced by variations of the sound propagation velocity within the craft supporting liquid medium.
6. System according to claim 5, wherein the corrected signals delivered at the output of the subtraction circuit are divided into 32 measured points successively extracted to provide at said processor output sea current speed values with respect to sea bottom of successive and contiguous water layers.
7. System according to claim 6, wherein a sampler comprised in said processor extracts said 32 measured values.
8. A liquid flow rate metering system on board comprising, in cooperation:
- a flow rate meter, based on Doppler effect for providing relative measurements of currents through a liquid medium, - a Doppler sonar system, for determining the speed of moving craft in relation to the liquid bottom and further for correcting said flow rate relative measurements, - a controlled switching means, for sequentially connecting said meter and said sonar system alternately to a single acoustic unit, - a control means for controlling said switching means operation and for actuating sequentially in turn the meter and the sonar system actually connected to said acoustic unit, - the said acoustic unit comprising groups of electro-acoustic transmitting and receiving transducers mounted within a fluid medium filled sealed casing which is inclined in relation to the vertical beam axes oriented towards acoustic waves transpa-rent casing base in contact with craft supporting liquid medium, the velocity of acoustic waves in the filling fluid being con-trollable by regulated and adjustable temperature of said fluid, whereby the difference between the measured flow rate and the determined speed of the craft provides at the output of a data processing device true flow rate in magnitude, direction and relative layer distribution.
- a flow rate meter, based on Doppler effect for providing relative measurements of currents through a liquid medium, - a Doppler sonar system, for determining the speed of moving craft in relation to the liquid bottom and further for correcting said flow rate relative measurements, - a controlled switching means, for sequentially connecting said meter and said sonar system alternately to a single acoustic unit, - a control means for controlling said switching means operation and for actuating sequentially in turn the meter and the sonar system actually connected to said acoustic unit, - the said acoustic unit comprising groups of electro-acoustic transmitting and receiving transducers mounted within a fluid medium filled sealed casing which is inclined in relation to the vertical beam axes oriented towards acoustic waves transpa-rent casing base in contact with craft supporting liquid medium, the velocity of acoustic waves in the filling fluid being con-trollable by regulated and adjustable temperature of said fluid, whereby the difference between the measured flow rate and the determined speed of the craft provides at the output of a data processing device true flow rate in magnitude, direction and relative layer distribution.
9. The combination in accordance with claim 8, wherein said control means is a master clock and said switching means is of logic circuits type, the switching from one position to the other being produced in a cycle with a duration which is at least equal to the longest transmission-reception cycle of the actuated system element.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA276,721A CA1093676A (en) | 1977-04-21 | 1977-04-21 | Liquid flow rate metering system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA276,721A CA1093676A (en) | 1977-04-21 | 1977-04-21 | Liquid flow rate metering system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1093676A true CA1093676A (en) | 1981-01-13 |
Family
ID=4108465
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA276,721A Expired CA1093676A (en) | 1977-04-21 | 1977-04-21 | Liquid flow rate metering system |
Country Status (1)
| Country | Link |
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| CA (1) | CA1093676A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109270295A (en) * | 2018-08-20 | 2019-01-25 | 南京世海声学科技有限公司 | A kind of underwater sound Doppler's flow-speed measurement method screened based on autocorrelation estimation and valid data |
-
1977
- 1977-04-21 CA CA276,721A patent/CA1093676A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109270295A (en) * | 2018-08-20 | 2019-01-25 | 南京世海声学科技有限公司 | A kind of underwater sound Doppler's flow-speed measurement method screened based on autocorrelation estimation and valid data |
| CN109270295B (en) * | 2018-08-20 | 2021-03-30 | 南京世海声学科技有限公司 | Underwater acoustic Doppler flow velocity measurement method based on autocorrelation estimation and effective data screening |
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