System for measuring the flow velocity of a liquid

Abstract

The invention relates to a system (100) for measuring the flow velocity of a liquid, in particular of a flow in an aquifer, the measurement system (100) comprising: - an assembly (E) of at least one sensor (1), each sensor (1) of the assembly (E) of sensors comprising: -- a body (2) configured to undergo a driving force of the liquid, -- a connecting element (3) connected to the body (2), the body (2) being configured to exert on the connecting element (3) a force depending on the driving force of the liquid, -- a force sensor (4) configured to determine the force exerted by the body (2) on the connecting element (3), - an electronic computing unit (30, 35) configured to determine, for each sensor (1) of the assembly (E) of sensors, a flow velocity of the liquid from the force determined by the force sensor (4) of the sensor (1).

Description

[0001] LIQUID FLOW VELOCITY MEASUREMENT SYSTEM

[0002] technical field

[0003] [1] The present invention relates to the field of liquid flow characterization. More particularly, the present invention relates to the characterization of liquid circulation in aquifers, in particular flows in resurgences which may be submarine.

[0004] Previous technique

[0005] [2] Water resources are likely to become scarce in many parts of the world, so it is desirable to improve the management of the various available resources. Among these, coastal or submarine groundwater resurgences can play a significant role, but are currently often poorly understood. Indeed, transfers in these resurgences are difficult to measure. Moreover, the equipment available to measure these transfers risks disturbing the flow and is generally inaccurate. Transfers in coastal or submarine groundwater resurgences are therefore generally poorly understood.

[0006] [3] There is therefore a need to have means of measurement to measure these water transfers, in order to improve the management of water reserves.

[0007] Summary

[0008] [4] To this end, the invention proposes a system for measuring the flow velocity of a liquid, in particular a flow in an aquifer, the measuring system comprising:

[0009] - a set of at least one sensor, each sensor in the sensor set comprising:

[0010] -- a body configured to withstand a driving force from the liquid,

[0011] -- a connecting element attached to the body, the body being configured to exert a force on the connecting element that depends on the driving force of the liquid,

[0012] - a force sensor configured to determine the force exerted by the body on the connecting element, - an electronic calculation unit configured to determine, for each sensor in the sensor set, a liquid flow velocity from the force determined by the force sensor of said sensor.

[0013] [5] The measurement system can be used for a wide variety of flows. Simply distribute all the sensors throughout the flow to be characterized. A flow velocity at various points can thus be obtained. From this, the flow rate can be deduced.

[0014] [6] The features listed in the following paragraphs can be implemented independently of each other or in any technically possible combination:

[0015] [7] The force exerted on the connecting element is in the opposite direction to the driving force exerted by the liquid flowing over the sensor body.

[0016] [8] According to one embodiment of the proposed flow velocity measurement system, the connecting element of each sensor in the sensor set is flexible.

[0017] [9] By 'flexible connecting element', we mean that the shape taken by the connecting element depends on the driving force received.

[0018] The connecting element can therefore orient itself freely in the direction of fluid flow. The sensor can thus adapt naturally to any variations in the liquid's flow direction. In particular, the sensor can operate independently of the liquid's flow direction.

[0019]

[0010] The connecting element of each sensor is, for example, a flexible cable.

[0020]

[0011] The force exerted on the connecting element can be a tension force.

[0021]

[0012] According to one embodiment, the flow velocity measurement system may include a support configured to be fixed to a wall of an aquifer, and the connecting element of each sensor in the sensor set is integral with the support.

[0022]

[0013] The support ensures the positioning of each sensor.

[0014] The mechanical link between the connecting element of each sensor in the sensor assembly and the support may include a ball joint.

[0023] The connecting element can thus orient itself freely in the direction of the flow.

[0024]

[0015] Each sensor may include a single connecting element configured to be attached to the support.

[0025]

[0016] The support can be rigid.

[0026]

[0017] The support can extend in a plane.

[0027]

[0018] According to one embodiment of the flow velocity measurement system, the sensors of the sensor set can be spatially distributed on the support along an axis.

[0028]

[0019] The sensors can thus be aligned in order to characterize the flow at several points.

[0029]

[0020] According to one embodiment of the flow velocity measurement system, the sensors of the sensor set can be spatially distributed on the support along two transverse directions.

[0030]

[0021] The sensor set can thus determine the flow velocity at various points of a measurement surface, which makes it possible to fully characterize the flow in a given section.

[0031]

[0022] The sensors can thus form a two-dimensional network.

[0032]

[0023] According to one embodiment of the flow velocity measurement system, the support may comprise:

[0033] - a frame configured to be fixed to a wall adjacent to a liquid flow channel,

[0034] - a set of linear elements fixed to the armature, the linear elements being spaced apart from each other, and each sensor can be fixed to a linear element of the set of linear elements.

[0035]

[0024] The frame and linear elements ensure precise positioning of the sensors.

[0025] The linear elements can be rods.

[0036] The stems can be rigid.

[0037]

[0026] The linear elements can be cables, for example metal cables.

[0038]

[0027] The frame can be configured to encompass a perimeter of an outlet channel of an aquifer.

[0039]

[0028] The armature can form a closed frame.

[0040]

[0029] The armature can have the shape of a polygon, for example a regular polygon.

[0041]

[0030] The support rods can extend parallel to a first direction.

[0042]

[0031] A first part of the support rods can extend parallel to a first direction and a second part of the support rods can extend parallel to a second direction transverse to the first direction.

[0043] The second direction forms a non-zero angle with the first direction.

[0044] According to one example of implementation, the second direction can be perpendicular to the first direction.

[0045]

[0032] The support rods can be rigid.

[0046]

[0033] The support rods can, for example, be cylindrical.

[0047]

[0034] The support rods can be spaced at a constant distance.

[0048]

[0035] The support frame is, for example, made of stainless steel.

[0049]

[0036] The support rods are, for example, made of stainless steel.

[0050]

[0037] The sensors can be arranged at a distance from each other in a first direction.

[0051]

[0038] The sensors can be arranged at a distance from each other along a second direction transverse to the first direction.

[0052]

[0039] The support rods can all have the same profile.

[0053]

[0040] The characteristics stated above in the case where the linear elements are rods are also applicable in the case where the linear elements are cables.

[0041] According to another embodiment of the flow velocity measurement system, the support may comprise:

[0054] - a set of piles configured to be fixed to a wall adjacent to a liquid flow channel,

[0055] - a set of cables, each cable being attached to at least two piles of the pile set, and each sensor can be attached to one cable of the cable set.

[0056]

[0042] The elements forming the support are therefore lightweight and compact before deployment for measurements. This facilitates the transport of the equipment. Furthermore, this system can be deployed on outlets of very different shapes: it can adapt around any outlet channel.

[0057]

[0043] The cable assembly can be arranged so as to encompass a perimeter of an outlet channel of an aquifer.

[0058]

[0044] According to one embodiment of the proposed measurement system, all the sensors in the sensor set can be identical.

[0059]

[0045] According to one embodiment, some sensors in the sensor set may be of a different type from the other sensors in the sensor set.

[0060]

[0046] According to one embodiment of the flow velocity measurement system:

[0061] - the body of each sensor may exhibit rotational symmetry around an axis called the "axis of symmetry", and

[0062] - the connecting element can be connected to the body at a point on the axis of symmetry of revolution.

[0063]

[0047] Thus, the flow is symmetrical all around the sensor body. The resultant of the fluid forces applied to the body passes through the axis of rotational symmetry of the body. In other words, the sensor body generates no lift. Therefore, the resultant of the fluid forces applied to the body comprises only the drag force.

[0064]

[0048] The body of each sensor has, for example, the shape of a sphere.

[0065]

[0049] The measurement system may include, for each sensor, a device for attaching the sensor's connecting element to the support.

[0050] According to one embodiment of the flow velocity measurement system, the body of each sensor may include:

[0066] - an outer surface of approximately spherical shape, configured to be in contact with the liquid,

[0067] - an internal cavity,

[0068] - a communication orifice from the internal cavity to the external surface, configured to allow the internal cavity to fill with liquid, and the internal cavity of the body can be configured so that, when the external surface of the sensor is immersed in a liquid, the Archimedes' thrust exerted on the body of the sensor is equal in absolute value to the weight of the sensor.

[0069]

[0051] In other words, the sensor can have neutral buoyancy.

[0070]

[0052] The volume of the internal cavity of the body can be adjusted so that the buoyant force acting on the body's outer surface balances the sum of the body's weight and the weight of the water filling the sensor's internal cavity. Thus, the body tends neither to float nor to sink. The force exerted on the connecting element by the body is therefore only the reaction to the driving force applied by the flow of liquid over the body. The accuracy of the measurements is improved, since neither the weight of the sensor nor the buoyant force influences the measured force.

[0071]

[0053] In other words, the volume of the internal cavity of the body can be equal to the difference:

[0072] - of the volume delimited by the outer surface of the body and

[0073] - the ratio of the mass of the body and an estimated density of the liquid.

[0074]

[0054] The volume of the internal cavity of the body can be determined by the following equation, such that the weight of the sensor is opposed to the Archimedes' thrust and the sum of these two forces is zero:

[0075] [Math. 1 ] m2 V7 = V6 - mv with:

[0076] V7: volume of the internal body cavity,

[0077] V6: volume delimited by the outer surface of the body, m2: total mass of the sensor, mv: density of the liquid.

[0078]

[0055] The connecting element can pass through the body at a point in the body, and said point of passage can be diametrically opposite to the communication orifice.

[0079] Thus, the communication port does not disrupt the flow of liquid around the sensor body.

[0080]

[0056] According to one embodiment of the flow velocity measurement system, the body of each sensor may include a housing for receiving the force sensor.

[0081]

[0057] The force sensor may include a strain gauge.

[0082]

[0058] According to one example of an implementation of the measurement system, the force sensor may include:

[0083] - an elastic element configured to deform under the effect of the force exerted by the body on the connecting element,

[0084] - a linear variable differential transducer, configured to measure a deformation of the elastic element.

[0085]

[0059] The elastic element can be a spring, for example a helical spring.

[0086]

[0060] According to an embodiment of the flow velocity measurement system, in which each sensor has a projected area and a drag coefficient, the flow velocity can be determined, for each sensor, from the determined force, from the projected area of ​​the sensor body, from the drag coefficient, and from a density of the liquid.

[0087]

[0061] The flow velocity can be determined by the equation:

[0088] [Math. 2] with :

[0089] V: flow velocity in a flow direction, f: force determined by the sensor's force sensor, mv: density of the liquid,

[0090] Cx: drag coefficient of the sensor body,

[0091] Sp: projected surface area of ​​the sensor body in a plane orthogonal to the direction of the flow.

[0092]

[0062] According to one embodiment, the flow velocity can be a tabulated value as a function of the force measured by the force sensor of the sensor.

[0093]

[0063] According to one embodiment of the flow velocity measurement system, each sensor may comprise:

[0094] - an electronic computing unit configured to determine the flow velocity of the liquid in the vicinity of said sensor and to provide measurement samples comprising the determined flow velocity and an associated measurement time,

[0095] - an electrical energy storage battery,

[0096] - a data logger, configured to record the supplied measurement samples.

[0097]

[0064] According to one embodiment, each sensor may include a communication circuit, configured to transmit the recorded measurement samples.

[0098]

[0065] Each sensor can include its own equipment. A possible failure of one sensor has no influence on the other sensors. The availability of the measurement system is improved.

[0099]

[0066] According to another embodiment, the flow velocity measurement system may include a central electronic module configured to determine the flow velocity of the liquid in the vicinity of each sensor and to provide, for each sensor, measurement samples comprising the determined flow velocity and an associated measurement time, the central electronic module comprising:

[0100] - an electrical energy storage battery,

[0101] - a data logger, configured to record the measurement samples provided by each sensor,

[0102] - a communication circuit configured to transmit the recorded measurement samples.

[0067] The communication circuit may be an optical system.

[0103]

[0068] According to an example of implementation of the flow velocity measurement system, the central electronic module can provide measurement samples from all sensors in the sensor set synchronously.

[0104]

[0069] The measurement system may include a liquid temperature sensor.

[0105]

[0070] The measurement system may include a liquid electrical conductivity sensor.

[0106]

[0071] The measuring system may include a liquid pressure sensor.

[0107]

[0072] The measurement system may include a pH sensor for the liquid.

[0108]

[0073] The measurement system may include a sensor for the concentration of dissolved oxygen in the liquid.

[0109]

[0074] These additional sensors allow for the completion of the characterization of the flow liquid.

[0110]

[0075] The invention also relates to a system for measuring liquid flow rate, particularly at the outlet of an aquifer, comprising:

[0111] - a flow velocity measurement system as described above, configured to measure a flow velocity at a set of points distributed over an aquifer outlet surface,

[0112] - a computing unit configured to determine a liquid flow rate across the aquifer outlet surface based on the local flow velocity determined by each sensor in the measurement system and from a spatial distribution of the set of sensors in the measurement system.

[0113]

[0076] The calculation unit of the liquid flow measurement system may be separate from the calculation unit of the liquid flow velocity measurement system.

[0114] Brief description of the drawings

[0115]

[0077] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0116]

[0078] [Fig. 1] is a schematic cross-sectional and side view of an aquifer in which a flow velocity measurement system is installed,

[0079] [Fig. 2] is a schematic cross-sectional and side view of a flow velocity measurement system according to an embodiment of the invention,

[0117]

[0080] [Fig. 3] is a perspective view of a flow velocity measurement system according to another embodiment,

[0118]

[0081] [Fig. 4] is a perspective view of a flow velocity measurement system according to yet another embodiment,

[0119]

[0082] [Fig. 5] is a side view of a sensor forming part of the flow velocity measurement system of Figures 2 to 4,

[0120]

[0083] [Fig. 6] is a side and cross-sectional view of the sensor in Figure 5.

[0121] Description of the implementation methods

[0122]

[0084] To facilitate reading the figures, the various elements are not necessarily shown to scale. In these figures, identical elements bear the same reference numerals. Certain elements or parameters may be indexed, that is, designated, for example, as first element or second element, or first parameter and second parameter, etc. This indexing aims to differentiate similar, but not identical, elements or parameters. This indexing does not imply any priority of one element or parameter over another, and the designations may be interchanged. When it is specified that a device comprises a given element, this does not exclude the presence of other elements in that device.

[0123]

[0085] Figure 1 schematically represents a body of water L. The walls P of a basin delimit the body of water L. The walls P are, for example, formed of rocks. The symbol S designates the free surface of the body of water, that is to say the water / air interface.

[0124] This body of water L could correspond, for example, to a lake or an ocean. The Z-axis represents the vertical axis, and the X and Y axes represent two horizontal axes perpendicular to each other.

[0125]

[0086] The symbol C designates a channel opening into the bottom of the body of water L. The arrows designated by the symbol Q schematically represent the flow of water in channel C. In Figure 1, the circulation of water in channel C tends to fill the body of water L. Under other conditions, circulation in the opposite direction, tending to empty the body of water L, is possible. Under still other conditions, the liquid in channel C is in a state of equilibrium, and there is no flow in channel C.

[0126]

[0087] The sign A designates the outlet of the channel C, that is to say the place where the channel C opens into the bottom P of the body of water L.

[0127] A 100 flow velocity measurement system for a liquid is arranged at the outlet A of channel C, in order to characterize the flow in channel C.

[0128]

[0088] A system for measuring the flow velocity of a liquid, in particular a flow in an aquifer, is thus proposed.

[0129] The proposed measurement system 100 includes:

[0130] - a set E of at least one sensor 1, each sensor 1 of the sensor set E comprising:

[0131] - a body 2 configured to withstand a driving force from the liquid,

[0132] - a connecting element 3 linked to body 2, body 2 being configured to exert on connecting element 3 a force f depending on the driving force of the liquid,

[0133] - a force sensor 4 configured to determine the force f exerted by the body 2 on the connecting element 3,

[0134] - an electronic computing unit 30,35 configured to determine, for each sensor 1 of the sensor set E, a flow velocity V of the liquid from the force f determined by the force sensor 4 of said sensor 1.

[0135]

[0089] The proposed measurement system 100 can be used for a wide variety of flows. It is sufficient to distribute the set of sensors 1 throughout the flow to be characterized. A velocity at various points in the flow can thus be obtained. It is therefore possible to deduce the flow rate.

[0136]

[0090] Each sensor 1 of the sensor set E is configured to determine a local flow velocity, the drive force generated by the flow depending directly on the local flow velocity.

[0137] In other words, the flow velocity determined by a sensor 1 is an average velocity in the vicinity of the body 2 of the sensor 1. The vicinity is understood to be the surface area affected by the flow of the liquid on the body 2 of the sensor 1. For example, in the case of a spherical body, the vicinity corresponds to the diameter of the sphere.

[0138]

[0091] The body 2 of the sensor 1 is immersed in the liquid whose flow is to be characterized. In the illustrated example, the flowing liquid is, for example, water from an aquifer. This water can be fresh water, brackish water, or salt water.

[0139]

[0092] The body 2 of each sensor 1 is configured to undergo a driving force Fe generated by the liquid flowing over the body 2 of the sensor 1. This driving force Fe therefore depends on the local flow velocity, and on the shape of the body.

[0140] In Figure 5, the lines designated by the sign h schematically describe the flow of different fluid streams in the vicinity of the body 2 of a sensor 1.

[0141] The driving force Fe can include, in the most general case, a component called drag force and a component called lift force.

[0142] Drag force is a resistance force that acts in the same direction as the flow.

[0143] The lift force is applied in a direction transverse to the direction of the flow.

[0144]

[0093] The shape of the body 2 of the sensor 1 is chosen so as to generate a relatively strong drag, and a low lift.

[0145] The drag coefficient of body 2 of sensor 1 is greater than 0.2. Preferably, the drag coefficient of body 2 of sensor 1 is greater than 0.4, as for example in the case of a spherically shaped body.

[0146] The lift coefficient of body 2 of sensor 1 is less than 0.05. Preferably, the lift coefficient of body 2 is equal to 0, as in the case where body 2 has a symmetrical shape with respect to the direction of flow.

[0147]

[0094] The force f exerted on the connecting element 3 is in the opposite direction to the driving force Fe exerted by the liquid flowing over the body 2 of the sensor 1.

[0148] In other words, the connecting element 3 resists the driving force Fe exerted by the flow of the fluid streams h on the body 2 of the sensor 1, and in the vicinity thereof.

[0149]

[0095] The number of sensors 1 in the set E of sensors 1 can be arbitrary. The set E of sensors 1 can include a single sensor. In this case, the flow is characterized at a single point, which can be, for example, the center of the flow that one seeks to characterize.

[0150] The number of sensors 1 in the set E of sensors 1 is generally between 10 and 30.

[0151]

[0096] In the case where the sensor array E comprises several sensors, a velocity field can be determined at various points in the liquid flow. In other words, the measurement system 100 makes it possible to determine the local flow velocity at different points spatially distributed within a flow section A of the flow.

[0152]

[0097] According to one embodiment of the proposed flow velocity measurement system 100, the connecting element 3 of each sensor 1 of the sensor assembly E is flexible.

[0153]

[0098] By 'flexible connecting element', we mean that the shape taken by the connecting element 3 depends on the driving force received by the body 2 of the sensor 1.

[0154] In particular, the connecting element 3 can have a different shape in the absence of a driving force received and when a driving force Fe is applied to the body 2.

[0155] An absence of received driving force corresponds to a static, or immobile, state of the liquid in which the sensor 1 is immersed.

[0156] The connecting element 3 can therefore orient itself freely in the direction of liquid flow. The sensor 1 can thus adapt naturally to any variations in the direction of liquid flow. In particular, the sensor can operate independently of the direction of liquid flow.

[0157]

[0099] The connecting element 3 of each sensor 1 is, for example, a flexible cable. The connecting element 3 is, for example, made of polyester and / or polyamide fibers.

[0100] The force f exerted on the connecting element 3 can be a tensile force. In other words, the driving force Fe exerted by the liquid flowing over the body 2 of the sensor 1 tends to elongate the connecting element 3.

[0158]

[0101] According to the illustrated example, the flow velocity measurement system 100 includes a support 10 configured to be fixed to a wall P of an aquifer, and the connecting element 3 of each sensor 1 of the sensor set 1 is integral with the support 10.

[0159] The support 10 ensures the positioning of each sensor 1.

[0160]

[0102] The mechanical link between the linking element 3 of each sensor 1 of the sensor assembly 1 and the support 10 may include a ball joint.

[0161] The connecting element 3 can thus orient itself freely in the direction of the flow.

[0162]

[0103] For each sensor 1, the connecting element 3 links the body 2 to the support 10.

[0163]

[0104] The support 10 is rigid.

[0164] Rigid means that the shape of the support 10 is not modified by the application of the force exerted on the connecting elements 3.

[0165]

[0105] The support 10 extends in a plane.

[0166] Support 10 can be a single piece. Support 10 can be formed from an assembly of several parts.

[0167]

[0106] According to the illustrated example, each sensor 1 comprises a single connecting element 3 configured to be attached to the support 10.

[0168]

[0107] According to the example in Figure 2, the sensors of the sensor set E are spatially distributed on the support 10 along an axis.

[0169] The sensors can thus be aligned to characterize the flow at several points along a line.

[0170]

[0108] According to the example in Figures 2 and 3, the sensors of the sensor set E are spatially distributed on the support 10 along two transverse directions D1, D2.

[0171] The set E of sensors 1 can thus determine the flow velocity at various points of a measurement surface, which allows the flow in a given section to be fully characterized.

[0172]

[0109] The sensors 1 thus form a two-dimensional network.

[0173] The angle between direction D1 and direction D2 can take any non-zero value.

[0174] The angle between direction D1 and direction D2 is preferably between 45° and 90°.

[0175]

[0110] According to the embodiments of the flow velocity measurement system 100 illustrated in Figure 2 and Figure 3, the support 10 comprises:

[0176] - a frame 11 configured to be fixed to a wall P adjacent to a liquid flow channel C,

[0177] - a set of linear elements 12 fixed to the armature 1 1 , the linear elements 12 being spaced apart from each other, and each sensor 1 is fixed to a linear element 12 of the set of linear elements.

[0178] The frame 11 and the linear elements 12 ensure precise positioning of the sensors in the sensor assembly E.

[0179]

[0111] The linear elements 12 can be rods.

[0180] The rods are fixed to the frame 11, for example parallel to each other. The linear elements 12 can also be cables, for example metal cables.

[0181] For example, the metal cables are stretched between two distinct points of the frame 11. For example, the cables connect two points located on either side of an axis of symmetry of the frame 11.

[0182]

[0112] The flow channel C is, for example, an outlet channel of an aquifer. The frame 1 is configured to encompass a perimeter of an outlet channel C of an aquifer. The outlet channel C opens by joining the wall P. The outlet of the outlet channel C is the junction with the wall P.

[0183]

[0113] The periphery of the outlet channel C forms the boundary of a flow surface A through which the liquid can flow. The armature 11 is radially external to this flow surface A, so that the entire flow can be measured. In other words, the area enclosed by the armature 11 is larger than the area of ​​the outlet of the outlet channel.

[0184]

[0114] The frame 1 1 can form a closed frame.

[0185] In the example of figure 3, the frame 11 is circular in shape.

[0186] According to unrepresented variants, the armature 11 can have the shape of a polygon, for example a regular polygon.

[0187]

[0115] Alternatively, the frame 1 1 can form an open, i.e., non-closed, structure. The structure preferably extends in a plane. For example, the structure can be U-shaped, with two parallel arms connected by a base extending transversely to the arms.

[0188]

[0116] The wall P can be horizontal. The wall P is here a part of the bottom of the body of water L. The wall P can be the ocean floor.

[0189]

[0117] The wall P can also be vertical.

[0190] The wall P can also present any angle with the horizontal plane.

[0191]

[0118] According to one embodiment, the rods 12 of the support 10 extend parallel to a first direction D1.

[0192]

[0119] According to the example in Figure 3, a first part of the rods 12 of the support 10 extend parallel to a first direction D1, and a second part of the rods 12 of the support 10 extend parallel to a second direction D2 transverse to the first direction D1.

[0193] The second direction D2 forms a non-zero angle with the first direction.

[0194] According to one example of implementation, the second direction D2 can be perpendicular to the first direction D1.

[0195]

[0120] The rods 12 of the support 10 are rigid.

[0196] As before, rigid means that the shape of the rods is not modified by the force experienced in reaction to the driving force Fe generated by the flow of liquid on the body 2 of the sensor 1 associated with this rod 12.

[0197]

[0121] The rods 12 of the support 10 are, for example, cylindrical.

[0198] In other words, the 12 rods have a circular cross-section.

[0199] For example, the rods 12 of the support 10 all have the same profile. The rods 12 are thus identical, except for their length, which may differ from one rod to another.

[0200]

[0122] The rods 12 of the support 10 can be spaced at a constant distance.

[0201]

[0123] The frame 1 1 of the support 10 is for example made of stainless steel.

[0202] For example, the rods 12 of the support 10 are made of stainless steel.

[0203] The reinforcement 11 of the support 10 and the rods 12 can thus withstand long-term immersion in a corrosive environment.

[0204]

[0124] The sensors 1 are arranged at a distance from each other along a first direction D1.

[0205] The sensors 1 are arranged at a distance from each other along a second direction D2 transverse to the first direction D1.

[0206]

[0125] The characteristics stated above in the case where the linear elements are rods 12 are also applicable in the case where the linear elements are cables.

[0207]

[0126] Figure 4 represents another embodiment of the flow velocity measurement system 100.

[0208] In this embodiment, support 10 comprises:

[0209] - a set of 13 piles configured to be fixed to a wall P adjacent to a liquid flow channel C,

[0210] - a set of cables 14, each cable 14 being attached to at least two piles 13 of the pile set, and each sensor 1 is attached to a cable 14 of the cable set.

[0211]

[0127] The elements forming the support 10 are thus lightweight and compact before deployment for measurements. This facilitates the transport of the equipment. Furthermore, this system can be deployed on outlets of very different shapes: it can be adapted very quickly around any outlet channel.

[0212]

[0128] The cable assembly 14 is, for example, arranged to encompass the perimeter of an outlet channel C of an aquifer.

[0129] According to the illustrated example, all the sensors 1 of the sensor assembly E are identical.

[0213] According to one embodiment, some sensors 1 of the sensor set E may be of a different type from the other sensors in the sensor set E.

[0214]

[0130] According to the example illustrated in Figure 5:

[0215] - the body 2 of each sensor exhibits rotational symmetry about an axis R called the "axis of symmetry", and

[0216] - the connecting element 3 is connected to the body 2 at a point on the axis of symmetry of revolution R.

[0217]

[0131] Thus, the flow is symmetrical all around the body 2 of the sensor 1. The resultant Fe of the fluid forces applied to the body 2 passes through the axis of rotational symmetry R of the body 2. In other words, the body 2 of the sensor 1 generates no lift. Thus, the resultant of the fluid forces applied to the body 2 comprises only the drag force. The accuracy of the measurements is therefore improved.

[0218]

[0132] The body 2 of each sensor 1 has, in the illustrated example, the shape of a sphere.

[0219]

[0133] The measuring system 100 includes, for each sensor 1, an attachment device 5 for the linking element 3 of the sensor 1 to the support 10.

[0220]

[0134] The attachment device 5 includes an element enabling a ball joint type mechanical connection, so that the connecting element 3 can be positioned in the direction of the flow.

[0221] The attachment device 5 is for example a carabiner that can be engaged in a loop formed at one end of the connecting element 3. The end where the loop is formed is the end opposite to the end connected to the body 2 of the sensor 1.

[0222]

[0135] Figure 6 details the internal elements of sensor 1, according to a particular embodiment.

[0223]

[0136] According to this embodiment of the flow velocity measurement system 100, the body 2 of each sensor 1 comprises:

[0224] - an outer surface 6 of substantially spherical shape, configured to be in contact with the liquid,

[0225] - an internal cavity 7, - a communication orifice 8 of the internal cavity 7 with the external surface 6, configured to allow the internal cavity 7 to fill with liquid.

[0226] The internal cavity 7 of the body 2 is configured so that, when the external surface 6 of the sensor 1 is immersed in a liquid, the Archimedes' thrust exerted on the body 2 of the sensor is equal in absolute value to the weight of the sensor 1. Since these two forces are in opposite directions and equal in absolute value, their resultant, that is to say their vector sum, is zero.

[0227]

[0137] In other words, the sensor 1 has neutral buoyancy. Once immersed in the liquid, which is stationary, the sensor 1 has no tendency to sink or float.

[0228]

[0138] The volume V7 of the internal cavity 7 of body 2 is adjusted so that the buoyant force received by the outer surface 6 of body 2 balances the sum of the weight of body 2 and the weight of the liquid filling the internal cavity 7 of sensor 1. Thus, body 2 tends neither to float nor to sink. The force f exerted on the connecting element 3 by body 2 is therefore only the reaction to the driving force Fe applied by the flow of the liquid over body 2. The accuracy of the measurements is improved, since neither the weight of sensor 1 nor the buoyant force contributes to the measured force f.

[0229]

[0139] In other words, the volume V7 of the internal cavity 7 of body 2 is equal to the difference:

[0230] - of the volume V6 delimited by the outer surface 6 of the body 2 and

[0231] - the ratio of the mass of body 2 and an estimated density mv of the liquid.

[0232]

[0140] In other words, the volume V7 of the internal cavity 7 of the body 2 is determined by the following equation, such that the weight of the sensor 1 is opposed to the Archimedes' thrust and the sum of these two forces is zero:

[0233] [Math. 1 ] m2 V7 = V6 - mv with:

[0234] V7: volume of internal cavity 7 of body 2,

[0235] V6: volume delimited by the outer surface 6 of the body 2, m2: total mass of the sensor 2, mv: density of the liquid.

[0141] The internal cavity 7 is delimited by an inner surface 17. When the sensor 1 is immersed, the cavity 7, initially empty of liquid and filled with air, fills with liquid through the orifice 8. In steady state, the internal cavity 7 is completely filled with liquid. The inner surface 17 of the cavity is in contact with the liquid.

[0236]

[0142] The density of the liquid is estimated as a function of the chemical composition of the liquid whose flow rate we want to measure.

[0237] For example, in the case of an aquifer, the density of the water can be estimated based on salinity and temperature.

[0238]

[0143] The connecting element 3 passes through the body 2 at a point 15 of the body 2, and said point of passage 15 is diametrically opposite to the communication orifice 8.

[0239] Thus, the communication orifice 8 does not disturb the flow of liquid around the body 2 of the sensor 1.

[0240]

[0144] The body 2 of each sensor 1 includes a receiving housing 9 for the force sensor 4.

[0241] The receiving housing 9 of the force sensor 4 is waterproof.

[0242] The linking element 3 is mechanically linked to the force sensor 4, so that the force sensor 4 measures the tension in the linking element 3.

[0243]

[0145] According to one embodiment, the force sensor 4 includes a strain gauge.

[0244]

[0146] According to another embodiment, the force sensor 4 comprises:

[0245] - an elastic element configured to deform under the effect of the force exerted by the body on the connecting element 3,

[0246] - a linear variable differential transducer, configured to measure a deformation of the elastic element.

[0247]

[0147] The elastic element can be a spring, for example a helical spring. The deformation of the elastic element is, for example, an elongation of the elastic element.

[0248] The elements of the force sensor 4 are not shown in the figures.

[0148] The body 2 of each sensor 1 can be made of plastic material. The body 2 is, for example, made of polymer, in particular polyester, polyethylene, or polyurethane.

[0249] Body 2 can, for example, be overmolded.

[0250]

[0149] The flow velocity V can be determined in different ways from the force f determined by the force sensor 4 of a sensor 1.

[0251] According to an embodiment of the flow velocity measurement system 100, in which each sensor 1 has a projected area Sp and a drag coefficient Cx, the flow velocity V is determined, for each sensor 1, from the force f determined, from the projected area Sp of the body 2 of the sensor 1, from the drag coefficient Cx, and from a density mv of the liquid.

[0252]

[0150] The flow velocity V is thus determined by the equation: [Math. 2] with :

[0253] V: flow velocity in a flow direction, f: force determined by force sensor 4 of said sensor 1, mv: density of the liquid,

[0254] Cx: drag coefficient of body 2 of sensor 1,

[0255] Sp: projected surface of body 2 of sensor 1 in a plane orthogonal to the direction of the flow.

[0256]

[0151] The projected surface area Sp of the body 2 of the sensor 1 and the drag coefficient are determined in the laboratory before use of the sensor 1.

[0257] A calibration curve can be produced, for example by regulating the flow velocity around sensor 2 to a known value, this known value being determined by another measuring instrument serving as a reference for carrying out the calibration.

[0258] The flow direction along which the flow velocity V is determined can also be designated by the term principal flow direction.

[0152] Other formulas for determining the flow velocity V as a function of the measured force f can also be used.

[0259]

[0153] According to one embodiment, the flow velocity V is a tabulated value as a function of the force f measured by the force sensor of the sensor.

[0260] The table is, for example, a single-entry table, this entry being the measured force f. The table includes, for example, 20 support points.

[0261] When the measured force f is a value between two consecutive support points, the flow velocity V is determined for example by linear interpolation between the value corresponding to the first of the two consecutive support points and the value corresponding to the second of the two consecutive support points.

[0262]

[0154] According to one embodiment of the flow velocity measurement system 100, each sensor 1 comprises:

[0263] - an electronic computing unit 30 configured to determine the flow velocity of the liquid in the vicinity of said sensor 1 and to provide measurement samples comprising the determined flow velocity and an associated measurement time,

[0264] - a 20V battery for electrical energy storage,

[0265] - a data logger 21, configured to record the supplied measurement samples.

[0266]

[0155] According to the illustrated example, each sensor 1 includes a communication circuit 22, configured to transmit the recorded measurement samples.

[0267]

[0156] Each sensor 1 thus comprises its own equipment, enabling data acquisition, calculations based on the acquired data, and transmission. A possible failure of one sensor has no influence on the other sensors. The availability of the measurement system 100 is thus improved.

[0268]

[0157] According to another embodiment, schematically illustrated in Figure 2, the flow velocity measurement system 100 comprises a central electronic module 35 configured to determine the flow velocity of the liquid in the vicinity of each sensor 1 and to provide, for each sensor 1, measurement samples comprising the determined flow velocity and an associated measurement instant.

[0269] The central electronic module 35 comprises:

[0270] - a 36V battery for electrical energy storage,

[0271] - a data logger 37, configured to record the measurement samples provided by each sensor 1,

[0272] - a communication circuit 38 configured to transmit the recorded measurement samples.

[0273]

[0158] The communication circuit 38 is, for example, an optical system.

[0274]

[0159] According to an example of implementation of the flow velocity measurement system 100, the central electronic module 35 provides the measurement samples from all the sensors 1 of the sensor set E 1 synchronously.

[0275]

[0160] In other words, the measurements are carried out simultaneously for all sensors 1. Simultaneous means that the time difference between the acquisition by two different sensors of the set of sensors is negligible compared to the rate of change of the observed phenomenon.

[0276]

[0161] The sampling period is, for example, between 1 second and 1 day. The sampling period is chosen according to the expected duration of use of the measuring system.

[0277]

[0162] Optionally, the measurement 100 may include other sensors, in order to characterize other physical parameters of the liquid.

[0278]

[0163] The measuring system 100 may include a liquid temperature sensor.

[0279] The 100 measurement system may include a liquid electrical conductivity sensor.

[0280] The 100 measurement system may include a liquid pressure sensor.

[0281] The 100 measurement system may include a liquid pH sensor.

[0282] The measurement system may include a sensor for the concentration of dissolved oxygen in the liquid.

[0283] These additional sensors allow for a more complete characterization of the flowing liquid.

[0164] Each additional sensor for a physical property of the liquid can be attached to the support 10 of the measuring system 100.

[0284] Each additional sensor for a physical property of the liquid is connected to the central electronic module 35.

[0285] In Figure 2, the additional sensors have not been shown.

[0286]

[0165] The invention also relates to a system for measuring 110 a flow rate of liquid, in particular at the outlet of an aquifer.

[0287] The 110 liquid flow measurement system comprises:

[0288] - a flow velocity measurement system 100 as described above, configured to measure a flow velocity at a set of points distributed over an outlet surface A of the aquifer,

[0289] - a computing unit 40 configured to determine a liquid flow rate through the outlet surface A of the aquifer as a function of the local flow velocity determined by each sensor 1 of the measuring system 100 and from a spatial distribution of the set of sensors 1 of the measuring system 100.

[0290]

[0166] The calculation unit 40 of the measuring system 110 of the liquid flow rate can be distinct from the calculation unit 30,35 of the measuring system 100 of the liquid flow velocity.

[0291]

[0167] The spatial distribution of the sensors 1 is determined by construction, that is to say that this spatial distribution is fixed by the way in which the different sensors 1 are fixed on the support 10.

[0292] In particular, the spacing of the sensors 1, along two transverse directions, allows for the modeling of a mesh of the outlet surface A through which the liquid flows. By integrating the data relating to the flow velocities at different points of the mesh and the distances between the different measurement points of the mesh, a flow rate through the outlet surface A of the aquifer can be calculated.

[0293]

[0168] According to one embodiment, the computing unit 40 of the measuring system 110 performs post-processing of the data acquired by the measuring system 100. In other words, the determination of the flow rate in the aquifer includes:

[0294] - a step of acquiring the flow velocity at various points in the flow, at a given instant,

[0295] - an iteration step of the acquisition step, for a set of successive instants,

[0296] - a step for storing acquired speeds,

[0297] - a step to collect stored velocities,

[0298] - a step of using the collected data to determine the flow rate.

[0169] According to another embodiment, the calculation unit 40 of the measuring system

[0299] 110 can process in real time the data acquired by the measurement system 100.

Claims

Demands

1. A measurement system (100) for the flow velocity of a liquid, in particular a flow in an aquifer, the measurement system (100) comprising: - a set (E) of at least one sensor (1), each sensor (1) of the set (E) of sensors comprising: -- a body (2) configured to undergo a driving force from the liquid, -- a connecting element (3) linked to the body (2), the body (2) being configured to exert on the connecting element (3) a force (f) depending on the driving force of the liquid, -- a force sensor (4) configured to determine the force (f) exerted by the body (2) on the connecting element (3), - an electronic computing unit (30,35) configured to determine, for each sensor (1) of the set (E) of sensors, a flow velocity (V) of the liquid from the force (f) determined by the force sensor (4) of said sensor (1).

2. Flow velocity measurement system (100) according to claim 1, wherein the connecting element (3) of each sensor (1) of the sensor assembly (E) is flexible.

3. Flow velocity measurement system (100) according to claim 1 or 2, comprising a support (10) configured to be fixed to a wall (P) of an aquifer, in which the connecting element (3) of each sensor (1) of the sensor assembly (1) is integral with the support (10).

4. Flow velocity measurement system (100) according to claim 3, wherein the sensors of the sensor assembly (E) are spatially distributed on the support (10) along an axis (D1).

5. Flow velocity measurement system (100) according to claim 3 or 4, wherein the sensors of the sensor assembly (E) are spatially distributed on the support (10) along two transverse directions (D1, D2).

6. A flow velocity measurement system (100) according to any one of claims 3 to 5, wherein the support (10) comprises: - a frame (1 1 ) configured to be fixed to a wall (P) adjacent to a liquid flow channel (C), - a set of linear elements (12) fixed to the armature (11), the linear elements (12) being spaced apart from each other, in which each sensor (1) is fixed to one of the linear elements (12) of the set of linear elements.

7. A flow velocity measurement system (100) according to any one of claims 3 to 5, wherein the support (10) comprises: - a set of piles (13) configured to be fixed to a wall (P) adjacent to a liquid flow channel (C), - a set of cables (14), each cable (14) being attached to at least two piles (13) of the pile set, in which each sensor (1) is attached to a cable (14) of the cable set.

8. A flow velocity measurement system (100) according to any one of the preceding claims, wherein: - the body (2) of each sensor exhibits rotational symmetry about an axis (R) called the axis of symmetry, and - the connecting element (3) is connected to the body (2) at a point on the axis of revolution symmetry (R).

9. A flow velocity measurement system (100) according to any one of the preceding claims, wherein the body (2) of each sensor (1) comprises: - an outer surface (6) of substantially spherical shape, configured to be in contact with the liquid, - an internal cavity (7), - a communication orifice (8) of the internal cavity (7) with the external surface (6), configured to allow the internal cavity (7) to fill with liquid, wherein the internal cavity (7) of the body (2) is configured so that, when the external surface (6) of the sensor (1) is immersed in a liquid, the Archimedes' thrust exerted on the body (2) of the sensor is equal in absolute value to the weight of the sensor (1).

10. Flow velocity measurement system (100) according to any one of the preceding claims, wherein each sensor (1) has a projected area (Sp) and a drag coefficient (Cx), and wherein the flow velocity (V) is determined, for each sensor (1), from the force determined, from the projected area (Sp) of the body (2) of the sensor (1), from the drag coefficient (Cx), and from a density (mv) of the liquid.

11. A flow velocity measurement system (100) according to any one of the preceding claims, wherein each sensor (1) comprises: - an electronic computing unit (30) configured to determine the flow velocity of the liquid in the vicinity of said sensor (1) and to provide measurement samples comprising the determined flow velocity and an associated measurement time, - a battery (20) for storing electrical energy, - a data logger (21), configured to record the supplied measurement samples.

12. Flow velocity measurement system (100) according to claim 11, wherein each sensor (1) includes a communication circuit (22), configured to transmit the recorded measurement samples.

13. A flow velocity measurement system (100) according to claim 11, comprising a central electronic module (35) configured to determine the flow velocity of the liquid in the vicinity of each sensor (1) and to provide, for each sensor (1), measurement samples comprising the determined flow velocity and an associated measurement time, the central electronic module (35) comprising: - a battery (36) for storing electrical energy, - a data logger (37), configured to record the measurement samples provided by each sensor (1), - a communication circuit (38) configured to transmit the recorded measurement samples.

14. A flow velocity measurement system (100) according to the preceding claim, wherein the central electronic module (35) synchronously provides measurement samples from all sensors (1) of the sensor assembly (E) (1).

15. A liquid flow measurement system (110), particularly at the outlet of an aquifer, comprising: - a flow velocity measurement system (100) according to any one of the preceding claims, configured to measure a flow velocity at a set of points distributed over an outlet surface (A) of the aquifer, - a calculation unit (40) configured to determine a liquid flow rate through the outlet surface (A) of the aquifer as a function of the local flow velocity determined by each sensor (1) of the measurement system (100) and from a spatial distribution of the set of sensors (1) of the measurement system (100).

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