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Skin friction drag measurements by LDV
Applied Optics
|March 25, 2010
Summary
A new laser Doppler velocimeter precisely measures fluid velocity within boundary layers. This technique accurately quantifies aerodynamic skin friction drag by measuring wall velocity gradients.
Area of Science:
- Fluid dynamics
- Aerodynamics
- Optical measurement techniques
Background:
- Boundary layer flow is critical in aerodynamics.
- Accurate measurement of skin friction drag is essential for vehicle design.
- Existing methods like hot-wire anemometry can perturb the flow.
Purpose of the Study:
- To develop a non-intrusive method for measuring fluid velocity in boundary layers.
- To directly measure aerodynamic skin friction drag.
- To provide a tool for controlling skin friction on aerodynamic bodies.
Main Methods:
- Utilized a laser Doppler velocimeter (LDV) with a microscope objective as the receiving lens.
- Achieved a spatial resolution of 40 micrometers for velocity measurements.
- Applied the LDV to measure velocity gradients at the wall for skin friction determination.
Main Results:
- Successfully measured fluid velocity within the boundary layer.
- Directly quantified aerodynamic skin friction drag.
- Experimental results for skin friction and velocity components showed good agreement with conventional instruments.
- Demonstrated non-perturbing flow measurement capabilities.
Conclusions:
- The developed laser Doppler velocimeter is effective for measuring fluid velocity and skin friction in boundary layers.
- This method offers a non-intrusive alternative to traditional instruments.
- The technique provides a valuable tool for aerodynamic research and development.
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