A flexible two-dimensional wall shear stress sensor and its preparation method

Abstract

The present invention discloses a flexible two-dimensional wall shear stress sensor and a preparation method thereof. The sensor includes: a flexible substrate; a force measuring unit disposed on the flexible substrate and configured to obtain the magnitude of the two-dimensional wall shear stress by detecting the temperature change amount thereof in a flow field; and a direction measuring unit located on the flexible substrate and disposed around the force measuring unit. The direction measuring unit is configured to perform an operation on the included angle between the direction measuring unit and the preset positive direction of the force measuring unit and the temperature change amount of the direction measuring unit in the flow field to obtain the included angle between the two-dimensional wall shear stress and the preset positive direction of the force measuring unit, and the included angle is used to represent the direction of the two-dimensional wall shear stress, realizing high-precision measurement of the magnitude and direction of the wall shear stress.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluid measurement, and particularly relates to a flexible two-dimensional wall shear stress sensor and a preparation method thereof. Background Art

[0002] Fluid wall shear stress is the tangential stress generated on the wall due to viscous action when the fluid flows through the surface of an object. It is the basis for studying the flow field boundary layer structure and its development of aircraft and underwater vehicles, and analyzing the flow mechanism. It plays an important supporting role in the aerodynamic and hydrodynamic design and optimization of aircraft and vehicles.

[0003] The external flow fields of aircraft and vehicles have complex three-dimensional characteristics of non-uniformity and unsteadiness, and the boundary layers of aircraft and vehicles are extremely vulnerable to interference and damage. How to measure the shear stress of the boundary layers of aircraft and vehicles with high dynamic accuracy has always been a difficult point in academic research and engineering exploration. Existing relatively mature wall shear stress measurement devices include Preston tubes, Stanton tubes, friction balances, bottom partition types, capacitive, piezoresistive strain type and other MEMS micro sensors. However, these devices will damage the flow field during the measurement process, and do not have the ability to measure two-dimensional wall shear stress, and cannot perform refined measurement on transverse turbulent vortices, making it difficult to be applied to flow mechanism analysis; wall shear stress measurement methods include oil film method, infrared thermal imaging, etc. However, the above measurement methods do not have the ability of accurate quantitative measurement, and it is difficult to meet the measurement requirements of high precision and high dynamic response. In recent years, flexible wall shear stress micro sensors have developed rapidly in measuring the shear stress of the boundary layers of aircraft and vehicles. However, they cannot accurately measure the flow direction, and the protruding leads will have a certain impact on the flow field. Therefore, they have not been applied in fields such as refined measurement of turbulence and spatio-temporal evolution of vortex field structures. Summary of the Invention

[0004] Based on this, the present invention provides a flexible two-dimensional wall shear stress sensor and a preparation method thereof, which solve the problem that existing flexible wall shear stress micro sensors cannot accurately measure the shear stress and the flow direction, and further solve the problem that the flexible wall shear stress micro sensor affects the flow field during the measurement process.

[0005] A flexible two-dimensional wall shear stress sensor provided by the present invention, the sensor includes:

[0006] A flexible substrate;

[0007] A force measuring unit, the force measuring unit is arranged on the flexible substrate; and is configured to obtain the magnitude of the two-dimensional wall shear stress by detecting the temperature change amount of the force measuring unit in the flow field;

[0008] A direction finding unit, which is located on the flexible substrate and is arranged around the force measuring unit; it is configured to calculate the angle between the direction finding unit and the preset positive direction of the force measuring unit and the temperature change amount of the direction finding unit in the flow field, so as to obtain the angle between the two-dimensional wall shear stress and the preset positive direction of the force measuring unit, and this angle is used to represent the direction of the two-dimensional wall shear stress.

[0009] Further, the direction finding unit is specifically configured to:

[0010] Based on the temperature change amount of the direction finding unit compared with the zero flow velocity state and the angle between the direction finding unit and the preset positive direction of the force measuring unit, calculate that the angle between the calculated two-dimensional wall shear stress and the preset positive direction of the force measuring unit is θ c , and

[0011]

[0012] wherein, ΔT i represents the temperature change amount of the i-th direction finding unit compared with the zero flow velocity state, λ i represents the angle between the i-th direction finding unit and the preset positive direction of the force measuring unit, and n represents the number of the direction finding units.

[0013] Further, the force measuring unit is a ring-shaped thermistor, and the direction finding unit is an arc-shaped thermistor, and the arc-shaped thermistor is arranged around the ring-shaped thermistor.

[0014] Further, the sensor further includes:

[0015] A force measuring lead unit, which is arranged on the flexible substrate and is connected to the force measuring unit, and the force measuring lead unit is used to lead out the signal on the force measuring unit;

[0016] A direction finding lead unit, which is arranged on the flexible substrate and is connected to the direction finding unit, and the direction finding lead unit is used to lead out the signal on the direction finding unit.

[0017] Further, the sensor further includes:

[0018] A flexible insulating layer, which is arranged between the force measuring lead unit, the direction finding lead unit and the force measuring unit, the direction finding unit, and the flexible insulating layer separates the force measuring lead unit, the direction finding lead unit from the force measuring unit, the direction finding unit;

[0019] The flexible insulating layer is provided with a ramp through hole, the ramp through hole connects the force measuring lead unit and the force measuring unit, and the ramp through hole connects the direction finding lead unit and the direction finding unit.

[0020] Further, the direction finding unit includes a first direction finding unit, a second direction finding unit, a third direction finding unit, and a fourth direction finding unit. The first direction finding unit, the second direction finding unit, the third direction finding unit, and the fourth direction finding unit are evenly distributed around the force measuring unit, and the distances from the first direction finding unit, the second direction finding unit, the third direction finding unit, and the fourth direction finding unit to the center of the force measuring unit are all equal.

[0021] Further, the force measuring unit includes:

[0022] A first ring-shaped thermistor and a second ring-shaped thermistor. The second ring-shaped thermistor is located inside the first ring-shaped thermistor, and the first ring-shaped thermistor and the second ring-shaped thermistor are in a parallel structure.

[0023] Further, the radius of the first ring-shaped thermistor is smaller than the average vortex radius.

[0024] Further, the second ring-shaped thermistor includes:

[0025] A first sub-ring-shaped thermistor located inside the first ring-shaped thermistor. One end of the first sub-ring-shaped thermistor and the second ring-shaped thermistor are in parallel;

[0026] A second sub-ring-shaped thermistor located inside the first sub-ring-shaped thermistor. The first sub-ring-shaped thermistor and the second sub-ring-shaped thermistor are in series;

[0027] A third sub-ring-shaped thermistor located inside the second sub-ring-shaped thermistor. The second sub-ring-shaped thermistor and the third sub-ring-shaped thermistor are in series;

[0028] And a fourth sub-ring-shaped thermistor located inside the third sub-ring-shaped thermistor. One end of the third sub-ring-shaped thermistor and the fourth sub-ring-shaped thermistor are in series, and the other end of the fourth sub-ring-shaped thermistor is in parallel with the other end of the first ring-shaped thermistor.

[0029] The present invention also provides a preparation method for a flexible two-dimensional wall shear stress sensor. The method includes:

[0030] Preparing a flexible substrate layer on a carrier;

[0031] Preparing a lead layer on the flexible substrate layer. The lead layer includes a force measuring lead unit and a direction finding lead unit;

[0032] A flexible insulating layer is provided on the lead layer. The flexible insulating layer is tightly bonded to the flexible substrate layer, and the lead layer is covered between the flexible insulating layer and the flexible substrate layer;

[0033] A ramp through-hole is prepared on the flexible insulating layer by wet etching;

[0034] A force measuring unit and a direction measuring unit are prepared on the flexible insulating layer. The force measuring unit is connected to the force measuring lead unit through the ramp through-hole, and the direction measuring unit is connected to the direction measuring lead unit through the ramp through-hole;

[0035] The flexible insulating layer is imidized by stepwise heating to form a polyimide film.

[0036] A flexible two-dimensional wall shear stress sensor provided by the present invention obtains the magnitude of the two-dimensional wall shear stress by detecting the temperature change of the force measuring unit; by arranging the direction measuring unit around the force measuring unit, and by detecting the temperature change of the direction measuring unit and the included angle between the direction measuring unit and the preset positive direction of the force measuring unit, the direction of the two-dimensional wall shear stress is obtained, realizing high-precision measurement of the magnitude and direction of the wall shear stress. Description of the Drawings

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0038] Figure 1 It is a structural schematic diagram of a flexible two-dimensional wall shear stress sensor provided by an embodiment of the present invention;

[0039] Figure 2 It is a structural schematic diagram of a force measuring unit and a direction measuring unit provided by an embodiment of the present invention;

[0040] Figure 3 It is the included angle θ between the two-dimensional wall shear stress obtained by the flexible two-dimensional wall shear stress sensor provided by an embodiment of the present invention and the preset positive direction of the force measuring unit c Schematic diagram of the relationship with the actual direction θ of the wall shear stress;

[0041] Figure 4 It is a flow schematic diagram of a preparation method of a flexible two-dimensional wall shear stress sensor provided by an embodiment of the present invention;

[0042] Figure 5 It is a structural schematic diagram of the preparation process of a flexible two-dimensional wall shear stress sensor;

[0043] Figure 6 A partial enlarged schematic diagram of a ramp through-hole provided by an embodiment of the present invention.

[0044] In the figure, 1 is a flexible substrate, 2 is a force measuring unit, 21 is a first ring-shaped thermistor, 22 is a second ring-shaped thermistor, 221 is a first sub-ring-shaped thermistor, 222 is a second sub-ring-shaped thermistor, 223 is a third sub-ring-shaped thermistor, 224 is a fourth sub-ring-shaped thermistor, 3 is a direction measuring unit, 31 is a first direction measuring unit, 32 is a second direction measuring unit, 33 is a third direction measuring unit, 34 is a fourth direction measuring unit, 4 is a force measuring lead unit, 5 is a direction measuring lead unit, 6 is a flexible insulating layer, and 7 is a ramp through-hole. Detailed implementation manners

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used in the description of this application in the specification are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the description and claims of this application and the above drawings are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the description and claims of this application or the above drawings are used to distinguish different objects and are not used to describe a specific order.

[0046] Reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0047] In order to make the objectives, technical solutions, and advantages of this application clearer, the following further details this application in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0048] In subsequent descriptions, the use of suffixes such as "module", "component", or "unit" to represent elements is only for the convenience of description of this application, and they do not have specific meanings themselves.

[0049] Embodiment 1

[0050] As Figure 1As shown in the figure, it is a schematic structural diagram of a flexible two-dimensional wall shear stress sensor provided by an embodiment of the present invention. The sensor includes:

[0051] A flexible substrate 1 and a force measuring unit 2, where the force measuring unit 2 is disposed on the flexible substrate 1 and is configured to obtain the magnitude of the two-dimensional wall shear stress by detecting the temperature change amount of the force measuring unit 2 in the flow field; a direction measuring unit 3, which is located on the flexible substrate 1 and is disposed around the force measuring unit 2 in a ring shape, and is configured to perform operations on the included angle between the direction measuring unit 3 and the preset positive direction of the force measuring unit 2 and the temperature change amount of the direction measuring unit 3 in the flow field to obtain the included angle between the two-dimensional wall shear stress and the preset positive direction of the force measuring unit 2, and this included angle is used to represent the direction of the two-dimensional wall shear stress.

[0052] Specifically, in this embodiment, the force measuring unit 2 is a heating component, which is heated to a constant temperature during operation. When the magnitude of the wall shear stress changes, the heat carried away by the force measuring unit 2 changes, and a signal indicating the heat change is fed back; the heating current of the sensor is received and adjusted to compensate for or reduce the heat change of the force measuring unit 2 caused by the change in the oncoming flow state. The resistance of the force measuring unit 2 remains unchanged. The greater the value of the wall shear stress, the greater the voltage across the two ends of the force measuring unit 2. The change in the wall shear stress magnitude is characterized by the change in the voltage across the two ends of the force measuring unit 2, that is

[0053]

[0054] where E w is the voltage across the two ends of the force measuring unit 2, and A T , B T are both fitting parameters obtained through calibration tests of the sensor, and τ is the wall shear stress.

[0055] Furthermore, the two-dimensional wall shear stress is obtained through the temperature change amount of the force measuring unit 2 in the flow field.

[0056] As Figure 2 shown in the figure, it is a schematic structural diagram of a force measuring unit and a direction measuring unit provided by an embodiment of the present invention. The direction measuring unit 3 is also a heating component, and the direction measuring unit 3 is distributed around the force measuring unit 2. In this embodiment, the preset positive direction of the force measuring unit is the positive x-axis direction of the central axis of the force measuring unit 2. The temperature change ΔT of the direction measuring unit 3 in the flow field and the included angle λ between the direction measuring unit 3 and the preset positive direction of the force measuring unit 2 are obtained, and the included angle between the two-dimensional wall shear stress representing the direction of the two-dimensional wall shear stress and the preset positive direction of the force measuring unit is obtained through operations.

[0057] The number of the direction measuring units 3 in this embodiment is not limited to meet the requirements of different scenarios.

[0058] The flexible two-dimensional wall shear stress sensor proposed in this embodiment obtains the magnitude of the two-dimensional wall shear stress by detecting the temperature change of the force measuring unit; by arranging the direction measuring units around the force measuring unit, and detecting the temperature change of the direction measuring unit and the included angle between the direction measuring unit and the preset positive direction of the force measuring unit, the direction of the two-dimensional wall shear stress is obtained, realizing high-precision measurement of the magnitude and direction of the wall shear stress.

[0059] Further, the direction measuring unit 3 is specifically configured as:

[0060] Based on the temperature change amount of the direction measuring unit compared with the zero flow velocity state and the included angle between the direction measuring unit and the preset positive direction of the force measuring unit, calculate that the included angle between the calculated two-dimensional wall shear stress and the preset positive direction of the force measuring unit is θ c , and

[0061]

[0062] where, ΔT i represents the temperature change amount of the i-th direction measuring unit compared with the zero flow velocity state, and λ i represents the included angle between the i-th direction measuring unit and the preset positive direction of the force measuring unit, and n represents the number of the direction measuring units.

[0063] Specifically, the temperature difference change between the upstream and downstream of the direction measuring unit 3 caused by the flow direction change can be represented by ΔT x , ΔT y , then:

[0064]

[0065] In the formula, ΔT represents the temperature boundary layer change matrix of the force measuring unit 2, which can be decomposed into the temperature change vector ΔT x in the x direction and the temperature change vector ΔT y in the y direction; ΔT 0 represents the temperature difference between the force measuring unit 2 and the environment; i and j respectively represent the unit vectors in the x and y directions; θ represents the wall shear stress direction, and λ i represents the included angle between the i-th direction measuring unit 3 and the positive direction of the x-axis, and ΔT i represents the temperature change amount of the i-th direction measuring unit compared with the zero flow velocity state.

[0066] Obtained through the above formula (1), based on the temperature change amount of the direction measuring unit compared with the zero flow velocity state and the included angle between the direction measuring unit and the preset positive direction of the force measuring unit, the formula for calculating the included angle θ c between the calculated two-dimensional wall shear stress and the preset positive direction of the force measuring unit is

[0067]

[0068] The specific direction of the two-dimensional wall shear stress can be accurately obtained through the above formula (2).

[0069] In some embodiments, the force measuring unit is an annular thermistor, the direction measuring unit is an arc-shaped thermistor, and the arc-shaped thermistor is arranged around the annular thermistor.

[0070] Specifically, the force measuring unit 2 is a disc-shaped thermistor, and the direction measuring unit 3 is an arc-shaped thermistor, which can make the measurement accuracy of the wall shear stress and its direction higher.

[0071] As Figure 1 shown, in some embodiments, the sensor further includes: a force measuring lead unit 4, arranged on the flexible substrate 1 and connected to the force measuring unit 2, and the force measuring lead unit 4 is used to lead out the signal on the force measuring unit 2; a direction measuring lead unit 5, arranged on the flexible substrate 1 and connected to the direction measuring unit 3, and the direction measuring lead unit 5 is used to lead out the signal on the direction measuring unit 3.

[0072] Specifically, the force measuring lead unit 4 can be arranged on both sides of the force measuring unit 2 to lead out the signal on the force measuring unit 2, and the direction measuring lead unit 5 is arranged at both ends of the direction measuring unit 3 to lead out the signal in the direction measuring unit 3, which is more convenient and accurate when measuring the signal.

[0073] As Figure 1 shown, in some embodiments, the sensor further includes:

[0074] a flexible insulating layer 6, the flexible insulating layer 6 is arranged between the force measuring lead unit 4, the direction measuring lead unit 5 and the force measuring unit 2, the direction measuring unit 3, and the flexible insulating layer 6 separates the force measuring lead unit 4, the direction measuring lead unit 5 from the force measuring unit 2, the direction measuring unit 3;

[0075] a ramp through hole 7 is arranged on the flexible insulating layer 6, the ramp through hole 7 connects the force measuring lead unit 4 and the force measuring unit 2, and the ramp through hole 7 connects the direction measuring lead unit 5 and the direction measuring unit 3.

[0076] Specifically, in this embodiment, the force measuring lead unit 4, the direction measuring lead unit 5 are separated from the force measuring unit 2, the direction measuring unit 3 by the flexible insulating layer 6, and the force measuring lead unit 4 is connected to the force measuring unit 2 respectively through the ramp through hole 7, and the ramp through hole 7 connects the direction measuring lead unit 5 and the direction measuring unit 3, avoiding the influence, interference and damage of the leads on the flow field.

[0077] As Figure 2As shown, in some embodiments, the direction finding unit 3 includes a first direction finding unit 31, a second direction finding unit 32, a third direction finding unit 33, and a fourth direction finding unit 34. The first direction finding unit 31, the second direction finding unit 32, the third direction finding unit 33, and the fourth direction finding unit 34 are evenly distributed around the force measuring unit 2, and the distances from the first direction finding unit 31, the second direction finding unit 32, the third direction finding unit 33, and the fourth direction finding unit 34 to the center of the force measuring unit 2 are all equal.

[0078] Specifically, in this embodiment, by evenly distributing the first direction finding unit 31, the second direction finding unit 32, the third direction finding unit 33, and the fourth direction finding unit 34 around the force measuring unit 2, by detecting the temperature change around the force measuring unit 2, the angle θ between the two-dimensional wall shear stress calculated by the above formula (2) and the preset positive direction of the force measuring unit c The schematic diagram of the relationship with the actual direction θ of the wall shear stress is as Figure 3 shown. Through two tests and calculations, it is obtained that when the number of the direction finding units 3 is 4, the flow direction measurement error is within 2% within 360°.

[0079] As Figure 2 shown, in some embodiments, the force measuring unit 2 includes:

[0080] A first annular thermistor 21 and a second annular thermistor 22. The second annular thermistor 22 is located within the first annular thermistor 21. The first annular thermistor 21 and the second annular thermistor 22 are in a parallel structure.

[0081] Specifically, in this embodiment, the force measuring unit 2 is composed of the parallel connection of the first annular thermistor 21 and the second annular thermistor 22, which improves the heat generation uniformity of the force measuring unit 2, avoids the interference of the flow direction on the magnitude of the wall shear stress, and improves the measurement accuracy of the two-dimensional wall shear stress.

[0082] In some embodiments, the radius of the first annular thermistor 21 is smaller than the average vortex radius.

[0083] Specifically, by the radius of the first annular thermistor 21 being smaller than the average vortex radius, the sensor can be applied to unsteady flow fields and eddy current tests.

[0084] As Figure 2 shown, in some embodiments, the second annular thermistor 22 includes:

[0085] A first sub-ring-shaped thermistor 221, the first sub-ring-shaped thermistor 221 is located within the first ring-shaped thermistor 21, and one end of the first sub-ring-shaped thermistor 221 is connected in parallel with the first ring-shaped thermistor 21; a second sub-ring-shaped thermistor 222, the second sub-ring-shaped thermistor 222 is located within the first sub-ring-shaped thermistor 221, and the first sub-ring-shaped thermistor 221 is connected in series with the second sub-ring-shaped thermistor 222; a third sub-ring-shaped thermistor 223, the third sub-ring-shaped thermistor 223 is located within the second sub-ring-shaped thermistor 222, and the second sub-ring-shaped thermistor 222 is connected in series with the third sub-ring-shaped thermistor 223; and a fourth sub-ring-shaped thermistor 224, the fourth sub-ring-shaped thermistor 224 is located within the third sub-ring-shaped thermistor 223, one end of the third sub-ring-shaped thermistor 223 is connected in series with the fourth sub-ring-shaped thermistor 224, and the other end of the fourth sub-ring-shaped thermistor 224 is connected in parallel with the other end of the first ring-shaped thermistor 21.

[0086] Specifically, in this embodiment, by arranging the force measuring unit 2 into five circles from the inside to the outside, the length of the force measuring unit 2 is increased, thereby increasing the heat generation of the force measuring unit 2 and improving the sensitivity of the sensor.

[0087] Embodiment 2

[0088] As Figure 4 shown, it is a schematic flowchart of a preparation method of a flexible two-dimensional wall shear stress sensor provided by an embodiment of the present invention. The method includes:

[0089] Step S1: Prepare a flexible substrate layer on a carrier.

[0090] Specifically, Figure 5 it is a schematic structural diagram of a flexible two-dimensional wall shear stress sensor. As Figure 5 (1) shown, using a hard substrate as a process carrier, a flexible substrate layer is prepared with polyimide.

[0091] Step S2: Prepare a lead layer on the flexible substrate layer. The lead layer includes a force measuring lead unit and a direction measuring lead unit. Specifically, as Figure 5 (2) shown;

[0092] Step S3: Set a flexible insulating layer on the lead layer. The flexible insulating layer is tightly bonded to the flexible substrate layer, and the lead layer is covered between the flexible insulating layer and the flexible substrate layer;

[0093] Specifically, the flexible insulating layer is prepared by using a polyamic acid solution to obtain polyamic acid and making it tightly bonded to the flexible substrate layer to cover the lead layer, as Figure 5 (3) shown.

[0094] Step S4: Prepare a ramp through-hole on the flexible insulating layer by wet etching;

[0095] Specifically, the method for preparing the ramp through-hole is as follows: Use photoresist as a mask to expose the position to be etched. Utilize the characteristics of isotropic wet etching. Use an etching solution to etch the flexible polymer insulating layer to form a ramp through-hole. The etching proceeds at the same rate in all directions, thereby generating an edge with a certain angle. By controlling the solution concentration and reaction time, a smooth gentle slope is finally formed on the insulating layer. After depositing metal leads, paths can be formed on both sides of it, as Figure 5 (4) shows, as Figure 6 shown, which is a partially enlarged schematic diagram of a ramp through-hole provided by an embodiment of the present invention. The ramp through-hole is an inverted trapezoidal structure with rounded corners.

[0096] Step S5: Prepare a force measuring unit and a direction measuring unit on the flexible insulating layer. The force measuring unit is connected to the force measuring lead unit through the ramp through-hole, and the direction measuring unit is connected to the direction measuring lead unit through the ramp through-hole, as Figure 5 (5) shows;

[0097] Step S6: Imidize the flexible insulating layer by stepwise heating to form a polyimide film, as Figure 5 (6) shows.

[0098] Specifically, after completing all the above steps, detach the polyimide flexible substrate layer from the hard substrate, as Figure 5 (7) shows.

[0099] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "the", and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A flexible two-dimensional wall shear stress sensor, characterized in that, the sensor includes: a flexible substrate; a force measuring unit disposed on the flexible substrate; configured to obtain the magnitude of the two-dimensional wall shear stress by detecting the temperature change amount of the force measuring unit in the flow field; a direction measuring unit located on the flexible substrate and disposed around the force measuring unit; configured to calculate the angle between the two-dimensional wall shear stress and the preset positive direction of the force measuring unit by operating on the angle between the direction measuring unit and the preset positive direction of the force measuring unit and the temperature change amount of the direction measuring unit in the flow field, and the angle is used to represent the direction of the two-dimensional wall shear stress, and the preset positive direction of the force measuring unit is the positive x-axis direction of the central axis of the force measuring unit; the direction measuring unit is specifically configured to: calculate the angle between the two-dimensional wall shear stress and the preset positive direction of the force measuring unit as θ c based on the temperature change amount of the direction measuring unit compared to the zero flow velocity state and the angle between the direction measuring unit and the preset positive direction of the force measuring unit, and wherein, ΔT i represents the temperature change amount of the i-th direction measuring unit compared to the zero flow velocity state, λ i represents the angle between the i-th direction measuring unit and the preset positive direction of the force measuring unit, and n represents the number of the direction measuring units, the sensor further includes: a force measuring lead unit disposed on the flexible substrate and connected to the force measuring unit, and the force measuring lead unit is used to lead out the signal on the force measuring unit; a direction measuring lead unit disposed on the flexible substrate and connected to the direction measuring unit, and the direction measuring lead unit is used to lead out the signal on the direction measuring unit; the sensor further includes: a flexible insulating layer disposed between the force measuring lead unit, the direction measuring lead unit and the force measuring unit, the direction measuring unit, and the flexible insulating layer separates the force measuring lead unit, the direction measuring lead unit from the force measuring unit, the direction measuring unit; a ramp through hole is provided on the flexible insulating layer, and the ramp through hole connects the force measuring lead unit and the force measuring unit, and the ramp through hole connects the direction measuring lead unit and the direction measuring unit.

2. The flexible two-dimensional wall shear stress sensor according to claim 1, characterized in that, the force measuring unit is an annular thermistor, and the direction measuring unit is an arc-shaped thermistor, and the arc-shaped thermistor is disposed around the annular thermistor.

3. The flexible two-dimensional wall shear stress sensor according to claim 1, characterized in that, the direction measuring unit includes a first direction measuring unit, a second direction measuring unit, a third direction measuring unit, and a fourth direction measuring unit, and the first direction measuring unit, the second direction measuring unit, the third direction measuring unit, and the fourth direction measuring unit are evenly distributed around the force measuring unit, and the distances from the first direction measuring unit, the second direction measuring unit, the third direction measuring unit, and the fourth direction measuring unit to the center of the force measuring unit are all equal.

4. The flexible two-dimensional wall shear stress sensor according to claim 2, characterized in that, the force measuring unit includes: A first annular thermistor and a second annular thermistor, the second annular thermistor being located within the first annular thermistor, and the first annular thermistor and the first annular thermistor being in a parallel structure.

5. The flexible two-dimensional wall shear stress sensor according to claim 4, wherein, the radius of the first annular thermistor is less than the average vortex radius.

6. The flexible two-dimensional wall shear stress sensor according to claim 4, wherein, the second annular thermistor includes: a first sub-annular thermistor located within the first annular thermistor, with one end of the first sub-annular thermistor and the second annular thermistor being in parallel; a second sub-annular thermistor located within the first sub-annular thermistor, with the first sub-annular thermistor and the second sub-annular thermistor being in series; a third sub-annular thermistor located within the second sub-annular thermistor, with the second sub-annular thermistor and the third sub-annular thermistor being in series; and a fourth sub-annular thermistor located within the third sub-annular thermistor, with one end of the third sub-annular thermistor and the fourth sub-annular thermistor being in series, and the other end of the fourth sub-annular thermistor being in parallel with the other end of the first annular thermistor.

7. A method for manufacturing a flexible two-dimensional wall shear stress sensor, the method being used to manufacture the flexible two-dimensional wall shear stress sensor according to any one of claims 1 to 6, wherein, the method includes: preparing a flexible substrate layer on a carrier; preparing a lead layer on the flexible substrate layer, the lead layer including a force-measuring lead unit and a direction-measuring lead unit; setting a flexible insulating layer on the lead layer, the flexible insulating layer being tightly bonded to the flexible substrate layer, and covering the lead layer between the flexible insulating layer and the flexible substrate layer; preparing a ramp through-hole on the flexible insulating layer by wet etching; preparing a force-measuring unit and a direction-measuring unit on the flexible insulating layer, the force-measuring unit being connected to the force-measuring lead unit through the ramp through-hole, and the direction-measuring unit being connected to the direction-measuring lead unit through the ramp through-hole; imidizing the flexible insulating layer by stepwise heating to form a polyimide film.

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