High temperature gradient micro-sensors for flow separation control

Cecile GHOUILA-HOURIa,b

Romain VIARD c, Quentin GALLAS b, Eric GARNIER b, Alain MERLENa,b, Abdelkrim TALBIa, Philippe PERNOD a

aUniv. Lille, CNRS, Centrale Lille, Univ. Valenciennes, ISEN, UMR 8520 - IEMN, LIA LICS/LEMAC, F-59000 Lille, FrancebONERA, Chemin de la Hunière 91123 Palaiseau, France

cFluiditech, Thurmelec, 68840 Pulversheim, France

Flow separation control

2

• Adverse pressure gradient

• Sharp edges geometry

Flow separation

• Re-attaching a separated flow

• Avoiding / Delayingseparation

Flow separation control

• Real-time adaptation

• Energy saving

Closed loop

Gad-el-Hak

Journal of Aircraft 38 [2001]

Wall shear stress sensors

3

Need for:

• Time-average values: global state of the flow

• Time-resolved values: unsteady structures in the flow

• Direction of the wall shear-stress vector

Several technologies have been developed

• Floating-element sensors

• Optical sensors, micro-fences

• Thermal sensors (hot-film sensors)

J.J. Miau et al.

Sensors and

Actuators A: Physical

[2015]

T. Von Papen et al.

Sensors and

Actuators A: Physical

[2004]

Chandrasekharan et

al.

Journal of MEMS

[2011]

Thermal sensors

4

Hot-films are commonly used in aerodynamics

Calorimetric sensors:

• Another type of thermal sensor

• Use for mass-flow measurement

• Applications for medical domain, home-

appliance,…

Löfdahl and Gad-el-Hak

Meas. Sci. Technol.10 [1999]

Advantages

• Commercially available (Dantec Glue-on-Probe)

• Easy to implement at the wall

• Commercially available electronics

Well known disadvantages

• Insensitive to flow direction

• Substrate effects impact the dynamic response

Kuo et al

Micromachines [2012]

Outline

I. Design of the wall shear stress micro-sensors

II. Calibration in flat plate

III. Flow separation detection on a step-like obstacle

IV. Preliminary results on active flow control on a flap model

V. Preliminary results on a pressure thermal micro-sensor

VI. Conclusion & Perspectives

5

Design of the wall shear stress micro-sensors

I. Design of the wall shear stress micro-sensors

II. Calibration in flat plate

III. Flow separation detection on a step-like obstacle

IV. Preliminary results on active flow control on a flap model

V. Preliminary results on a pressure thermal micro-sensor

VI. Conclusion & Perspectives

6

Design of the wall shear stress micro-sensors

7

• Calorimetric wall shear stress sensor

• Metallic wires: 1 mm x 3 µm x 730 nm (central)/330 nm (lateral)

• Periodic SiO2 micro-bridges for mechanical support

• Uncoupled heater and measurement wires

• Patent by IEMN LICS/LEMAC

R. Viard, A. Talbi, P. Pernod, A. Merlen, and V. Preobrazhensky, “MiniaturisedSensor Comprising A Heating Element, AndAssociated Production Method,” 2013. FR2977886 (A1) 2013-01-18 WO2013008203 (A2) 2013-01-17 WO2013008203 (A3)2013-03-07 CN103717526 (A) 2014-04-09 EP2731908 (A2)2014-05-21 US2014157887 (A1) 2014-06-12 EP2731908 (B1)2015-09-09 DK2731908 (T3) 2015-12-21.

Micro-fabrication of the sensors

8

4mm30µm

• TCR: 2380 ppm/°C

• Elevation of temperature: 9°C/mW

Electrical and thermal characteristics

Flexible packagingApplied Physics Letters,

DOI 10.1063/1.4972402

[2016]

Calibration in flat plate

I. Design of the wall shear stress micro-sensors

II. Calibration in flat plate

III. Flow separation detection on a step-like obstacle

IV. Preliminary results on active flow control on a flap model

V. Preliminary results on a pressure thermal micro-sensor

VI. Conclusion & Perspectives

9

Wind tunnel

Wind tunnel characteristics• 30 cm x 30 cm test section

• Flow velocity up to 40 m/s

Wall shear stress evaluation

• Relation of Coles-Fernholz:

– 𝐶𝑓 = 2 ∙1

𝑘∙ ln 𝑅𝑒𝜃 + 𝐶

−2

– 𝑘 = 0.384

– 𝐶 = 4.127

– 𝑅𝑒𝜃 = Τ(𝜃 ∙ 𝑈∞) 𝜈

• Wall shear stress and skin friction coefficient

– 𝜏 =1

2∙ 𝜌 ∙ 𝑈∞

2 ∙ 𝐶𝑓

• Hot-wire probe measurements from 0.3 mm to 35 mm to provide the velocityprofile in the boundary layer and the experimental momentum thickness ϴ

11

Calibration on a flat plate

2 modes of operation: constant current and constant temperature modes

Calibration curves fitting 4th order polynomial

Sensibility to the flow direction

12

C. Ghouila-Houri et al. Applied Physics Letters, DOI 10.1063/1.4972402 [2016] & Sensors and Actuators A DOI10.1016/j.sna.2017.09.030 [2017]

Flow separation detection on a step-like obstacle

I. Design of the wall shear stress micro-sensors

II. Calibration in flat plate

III. Flow separation detection on a step-like obstacle

IV. Preliminary results on active flow control on a flap model

V. Preliminary results on a pressure thermal micro-sensor

VI. Conclusion & Perspectives

13

Flow separation due to sharp edges geometry

Experiment setup

• Obstacles of different heights• 38 mm

• 19 mm

14

Sensor location in the

recirculation region

Flow separation detection

15

MEMS response

Deduced wall

shear stress

variations

C. Ghouila-Houri et al.

Sensors and Actuators A

DOI10.1016/j.sna.2017.09.030

[2017]

Flow separation detection

16

• Obstacle 38 mm x 38 mm

• Varying distance between the sensor and the obstacle

• Upstream flow velocity: 25 m/s

• ReH = 61.103

H 𝑥

Small eddy near

the obstacle

Separation length

Reattachment

Reattached flow

Work in progress…

Preliminary results on active flow control on a flap model

I. Design of the wall shear stress micro-sensors

II. Calibration in flat plate

III. Flow separation detection on a step-like obstacle

IV. Preliminary results on active flow control on a flap model

V. Preliminary results on a pressure thermal micro-sensor

VI. Conclusion & Perspectives

17

Integration of the sensors in a flap model

18

12 micro-sensors integrated in the flapmodel

L1 wind tunnel in ONERA Lille (2.40 m of test section diameter)

Miniaturized electronics

Flow control with pulsed jets (Festo MHE2)

Work in progress…

First results of active flow control

19

Sensor near the leading edge

Control by Festo actuators MHE2 (20 g/s;

60 Hz for pulsed mode)

Efficiency to re-attach a separated flow

Separated flow

Attached flow

Thèse T. Charbert, ONERA

Thèse T. Charbert, ONERA

Preliminary results on a pressure thermal micro-sensor

I. Design of the wall shear stress micro-sensors

II. Calibration in flat plate

III. Flow separation detection on a step-like obstacle

IV. Preliminary results on active flow control on a flap model

V. Preliminary results on a pressure thermal micro-sensor

VI. Conclusion & Perspectives

20

Preliminary results on a pressure thermal micro-sensor

21

Pressure sensing based on Pirani effect, exploiting the pressure-dependent thermal conductivity of a gas at the molecular range

Dimensions Wires: 1 mm x 3 µm x 730 nm Bridges: 20 µm x 2 µm x 500 nm

Cavity reduced to 170 nm for maximum sensitivity at atmospheric pressure

C. Ghouila-Houri et al

Applied Physics Letters, vol. 111, issue 12 [2017]

Conclusion & Perspectives

I. Design of the wall shear stress micro-sensors

II. Calibration in flat plate

III. Flow separation detection on a step-like obstacle

IV. Preliminary results on active flow control on a flap model

V. Preliminary results on a pressure thermal micro-sensor

VI. Conclusion & Perspectives

22

Conclusion & Perspectives

Wall shear stress MEMS sensor designed for flow control

Fabrication using micro-machining techniques

High temperature gradient for low power

Low-cost mass production

Wind tunnel experiments

Wall shear stress static calibrations in CC and CT modes

Detection of flow separation due to a step-like obstacle

Integration of 12 MEMS sensors in a flap model and 1st results of active flow control

Introduction of a thermal based pressure sensor

Pirani principle

Maximum of sensitivity at atmospheric pressure

Perspectives

Improvement of the CT electronics

Dynamical calibration of the micro-sensors (wall shear stress and pressure)

Integration of a micro-sensor inside a synthetic jet slot

Closed-loop active flow separation control using the micro-sensors

23

Acknowledgments

Thank you for your attention !

Questions ?

24

Partners:

French National Research Agency (ANR) in the frame of the ANR ASTRID “CAMELOTT” project for financial support

ELSAT 2020 – CONTRAERO

RENATECH the French national nanofabrication network