Very high light scattering efficiency.
Good flow tracking capability
HFSB Helium
Filled Soap Bubbles
Larger than usual tracing particles
Neutrally Buoyant: 𝜌𝐻𝐹𝑆𝐵
𝜌𝐴𝑖𝑟≅ 1
Neutrally Buoyant: 𝜌𝐻𝐹𝑆𝐵
𝜌𝐴𝑖𝑟≅ 1
Introduction
Particle image velocimetry (PIV) is an optical measurement
technique providing instantaneous velocity vectors in a section of
a flow, which allows also turbulent and pressure field
analysis.
This technique is based on light scattering particles added to
the flow, which is illuminated by powerful light source with two
pulses separated by short time interval. The scattered light is
recorded onto two consecutive frames of a CCD camera. Analysing the
displacement of the particles between the two frames is possible to
measure the velocity of the flow. Recent developments, like
High-speed Tomographic PIV, allow three dimensional, time solved
measurements.
The characterization of large scale turbulent air flows are of
particular interest for industrial applications, in specific the
design and optimization of wind turbines, ground vehicles and
airplanes . In order to apply 3-D measurements in wide volumes,
technical issues must be resolved.
Aim of the Project
Example of 2-D PIV: Velocity field around an automobile
Application of Particle Image
Velocimetry in large, industrial
wind tunnels
Constrains and Problems:
PhD Candidate: Giuseppe Caridi Department: AWEP Section:
Aerodynamics Supervisor: F. Scarano Promoter: F. Scarano Start
date: 1-11-2013 Funding: STW Cooperations: La Vision Type:
Scientific
Large observation areas
Limited power of light source
Finite scattering efficiency of tracer particles
Limited resolution of the CCD sensors
High operational costs of the wind tunnel
Possible Solution
Aero
space
Engin
eering
2006
Tomographic PIV development
2009
2014
Year Dimension of the field of View
A way to study the reliability of the measurement techniques is
to analyze simple phenomena. Below is represented the evolution of
the measured field of view in the last years on the wake of a
cylinder.
160 cm3
13 cm3
4000 cm3
Using HFSB
PIV SETUP
The development of PIV techniques using HFSB for wind tunnel
application involve efforts on two fronts:
Technical Theoretical
• Aerodynamic behaviour of HBSB in different flow regimes.
• Analysis of tracking capabilities of the HFSB
• Injection of the Bubbles in the flow
• Illumination of the region of interest
• Image-processing
The figure shows the comparison of the stream lines generated
with the HFSB and the micro size droplets, commonly used in
PIV.
Methodology
