DirectShear-2D

$9,147$12,347

DirectShear-2D™ is a dual-axis capacitive wall shear stress sensor, providing direct, vector skin-friction measurements in complex, three-dimensional turbulent flows.

DirectShear-2D is a natural extension of IC2’s original capacitive DirectShear™ sensing system, an industry-first microelectromechanical systems (MEMS) direct wall shear stress sensor.

The 2D, or dual-axis, version of this sensor allows for scientists to obtain point vector measurements of turbulent boundary layers. With its easy-to-use, non-intrusive housing and unprecedented dynamic range, DirectShear-2D sensors provide aerospace engineers with a new tool to improve fundamental understanding of complex, three-dimensional flows and validate computational models, paving the way for the future of efficient aircraft.

Originally developed for NASA, the capacitive sensors are now commercially available and are ideal for precise skin friction measurements in wind tunnels. Click here to see how NASA is utilizing DirectShear sensors.

For typical applications, please see our DirectShear product line.

For high-temperature applications, please see our DirectShear-Optical product line.

Click here to learn more about the Complete Shear Stress Measurement System that leverages additional PXI hardware to create a full measurement solution.

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SKU: CS-2D Series Category:

Lead Time and Pricing

Lead Time

12-16 Weeks

Sensor

Sensor Head (+$5,499)

Control Unit

PXI (+$3,299), H2U (+$6,249)

Cable Length

2 meters (+$349), 5 meters (+$449), 10 meters (+$599)

directshear-2d-control-unit-options
WirelessArray Connection Diagram

A Guide to Wall Shear Stress Measurement

Good Data Acquisition Case Study: The IC2 Complete Shear Stress Measurement System

DirectShear-2D is a dual-axis, instrumentation-grade, robust, high-bandwidth, high-resolution, silicon micromachined differential capacitive wall shear stress sensor for subsonic and transonic applications.

The sensor system enables localized, non-intrusive, vector measurement of mean and fluctuating wall shear stress for characterization of complex boundary-layer flows in ground-test facilities.

The design of next-generation air vehicles with increased efficiency cannot be developed without considerable research on the character and dynamics of unsteady, complex, three-dimensional flows. Specifically, some of the most difficult problems in the design of high-efficiency subsonic aircraft are associated with flow control technologies for viscous drag reduction. Time-resolved measurements of skin friction are needed to quantify the underlying transition and turbulence physics present in three-dimensional flows occurring on various aircraft that lead to increased drag and fuel consumption.

Features

  • Micromachined floating element shear stress sensor
  • Time-resolved, two-dimensional, direct wall shear stress measurements
  • Compact, robust sensor package for flush mounting
  • Optimized Sensor Control Unit for high dynamic range and bandwidth
  • Two sensor models to address different sensitivity/bandwidth applications
  • Ability to measure mean and fluctuating quantities
  • Integrated rechargeable lithium-ion battery system minimizes power line noise
  • Multi-pin shielded sensor connector provides supply voltages and carrier signals
  • System status and battery voltage LED indicators

Benefits

  • Direct measurement of wall shear stress — no heat transfer calibration required
  • Non-intrusive — minimal flow disturbance
  • Simultaneous mean and fluctuating wall shear stress measurements
  • High resolution, dynamic range and bandwidth
  • Highly accurate, quantitative measurements
  • Ability to place in arbitrary flow to measure wall shear stress vectors

Applications

  • Point vector wall shear stress measurements in an arbitrary flow
  • Low-speed wind tunnels
  • Instrumentation-grade skin friction sensing
  • Aerodynamic drag research
  • Detection of flow separation
  • Wind tunnel instrumentation

Sensor Head Housing Details

  • Non-intrusive — backside contacts for minimal flow disturbance
  • Standard stainless steel cylindrical housings available with or without shoulder and key alignment and
  • Detachable cable assembly
  • Multiple sensor head form factors, materials and finishes available to meet installation requirements.
  • Custom housings/materials available
  • 2 sensor models available for different applications (see Specifications table)
Model Shear Stress (Pa) Bandwidth (kHz) Sensitivity (mV/Pa) Resolution (mPa) Element Size
CS-2110 50 1.5 30 0.2 2mm x 2mm
CS-2210 300 5 1 2 1mm x 1mm

The following additional components and specifications are recommended for AC and DC testing/calibration with the capacitive sensor control unit:

  • 2 – RG58 coaxial cables with BNC connectors
  • Data acquisition system (DAQ) – AC/DC measurement
    • Sensing Range: ±1, ±5, ±10V – sensor dependent (see datasheet)
    • Resolution: 18+ bits
    • Sampling frequency: sensor dependent – adequate sample rate and anti-alias filter to support sensor bandwidth
  • Digital multimeter – DC measurement only
    • 6.5 digits with power line cycle (PLC) integration
    • DAQ or PC connection (e.g., GPIB)

Click here to learn more about the Complete Shear Stress Measurement System that leverages additional PXI hardware to create a full measurement solution.

Related Publications

A Flush-Mounted Dual-Axis Wall Shear Stress Sensor

Characterization of a Fully-Differential, Dual-Axis, Capacitive Wall Shear Stress Sensor System for Low-Speed Wind Tunnels

Development of a Two-Dimensional Wall Shear Stress Sensor for Wind Tunnel Applications

Related Projects

Fully-Differential Skin Friction Sensor Hardware and Calibration Method Development

Capacitive Vector Skin Friction Measurement Systems for Complex Flow Fields

MEMS Skin Friction Sensor

Frequently Asked Questions

What are DirectShear sensors?

DirectShear sensors provide a direct measurement of the wall shear stress via MEMS transduction technologies, eliminating the limitations of the indirect methods and vastly improving the accuracy of the measured data, enabling engineers to better understand critical aerodynamic effects and design aircraft to fly more efficiently.

Why is directly measuring wall shear stress important?

Prior to the release of IC2’s DirectShear sensors, wall shear stress was traditionally difficult to measure. Previous methods relied upon indirect approaches by measuring a different fluid property, such as heat transfer rate, and relating it back to shear stress empirically. That process usually requires making several assumptions and carefully controlling the environment, limiting the usefulness of these methods and the accuracy of the resulting data.

What is the typical application for DirectShear-2D Sensors?

DirectShear-2D Sensors are typically used in low-speed wind tunnel testing applications that require point vector wall shear stress measurements such as complex, three-dimensional turbulence research and detection of flow separation.

What is the operating temperature range for DirectShear Sensors?

DirectShear and DirectShear-2D models are specified for 0-50°C operating temperature. DirectShear-Optical sensors have an operating range of 0-400°C.

What is the difference between the H2U and PXI control units?

The H2U version is a standalone unit that runs on its own battery powered system and provides location flexibility, but is the larger and more expensive of the two options. The PXI model was developed to provide our customers a minimized overall footprint for the control unit and to take advantage of the PXI chassis form factor and power combined with the possibility to use a PXI-based system for the entire measurement capability.

Does each sensor need its own control unit?

Yes. Each sensor requires a dedicated control unit and each unit supports a single sensor at a time; however, multiple sensors can be paired with a single control unit in cases where spares or different sensor types are desired. Engineering services are available for customers who desire custom configurations of control units to support multiple sensors.

How do acceleration forces affect the sensor?

The sensor can survive large accelerations; more than 200g. The floating element’s small size and mass limit any significant inertial loads. However, accelerations will affect the output of the sensor. To account for acceleration, an additional accelerometer should be placed near the DirectShear sensor and the coherent power between the DirectShear sensor and the accelerometer should be subtracted from the measurement. IC2 provides the acceleration sensitivity data in the calibration packet included with each sensor purchase. IC2 is currently working on a future generation of the sensor that will compensate for acceleration automatically. Please contact IC2 for additional information regarding acceleration compensation.

Are DirectShear Sensors NIST traceable?

IC2 currently calibrates the dynamic response of its sensors in an acoustic plane wave tube and is working on a new Mean Shear Facility for improved calibration capabilities. DirectShear sensor calibrations are not NIST traceable because no standard yet exists. Our DirectShear sensor is the first of its kind on the market that makes this measurement. It is in our purview and we have had discussions with NIST about creating a standard.

How is the sensor typically mounted to the wall of a test section?

The sensor head may be placed in any known angular orientation with respect to the sensing axes. Angular misalignment during installation can result in increased uncertainty due to cross-axis sensitivity. Installation of the sensor head with the alignment key on the upstream side ensures alignment with the critical sensing axis. The sensor head should be inserted until the surface of the sensor head is flush with the facility wall. Proper design of the sensor installation port will provide repeatable installation depths and alignment via use of the shoulder and alignment key on the sensor head. Please contact IC2 for support with sensor installation.

How cautious should I be when handling the sensor?

The sensing element (the front face) is extremely fragile. Any physical contact with the exposed sensing element can cause damage to the sensor. A protective cap is provided for handling purposes and should be used to keep the sensor face covered at all times when not in use. Proper sensor cleaning procedures are outlined in the provided User Manual.