XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2795
their applications are limited to transparent flows. Hot wire
probes (Hultmark, et al., 2011 Amini et al., 2013 2016a
2016b 2017 Amini and Xie 2020) have high spatial and
temporal resolution in turbulence quantification, but they
are susceptible to environmental factors. Conductivity
probes (Xu, Finch &Huls, 1992 Maldonado et al., 2008)
are techniques that can quantify turbulence in multiphase
flows, but their spatial resolutions are limited. Lagrangian
Particle Tracking (Kasagi and Matsunaga, 1995 La Porta,
Voth, Bodenschatz, 2001) can reveal particle trajectories
in multiphase flows, but are limited to transparent fluids
with weak index of refraction variations. Positron Emission
Particle Tracking (Guida et al., 2009 Chiti et al., 2011
Cole, et al., 2014, 2022, 2023 Mesa, et al., 2021) has been
used to quantify hydrodynamics. The main challenge is
how to determine the tracer location within dynamic multi-
phase flows (Cole, et al., 2022). Recent developments show
that PEPT can detect turbulent structures at macroscale
lengths by calculating the turbulent kinetic energy (TKE)
experienced by a PEPT tracer particle in a lab cell (Cole,
et al., 2023). Piezoelectric Vibration Sensors measure pres-
sure fluctuations and can determine velocity, acceleration,
strain, and force, which can be used to quantify turbulence
in multiphase flows (Bakker et al., 2009 Tabosa et al.,
2012 Meng et al. 2014a, 2014b, 2015, 2016). Electrical
Resistance Tomography (Meng et al., 2014, 2015 Xie et
al., 2016 Xie and Li, 2019 Xie 2021 2022) can measure
velocity fluctuation in multiphase flows, however, its tem-
poral and spatial resolutions need to be improved.
TURBULENCE MEASUREMENT
TECHNIQUES
Laser Doppler Anemometry (LDA)
Laser Doppler Anemometry (LDA), also called Laser
Doppler Velocimetry, utilizes the Doppler shift in a laser
beam to calculate the velocity of a transparent or semi-
transparent fluid seeded with tracing particles. In the early
1960s, the helium-neon laser was developed. The laser was
monochromatic, collimated, and coherent making it ideal
for researching fluid flow (Keating, 1988). The principle
of a LDA system is depicted in Figure 2. When entrained
particles pass through the fringes, laser light is reflected,
collected, and focused on a photo-detector. The fluctuating
frequency represents the magnitude of the particle’s veloc-
ity and its direction on the plane created by the two laser
beams. The LDA’s high temporal and spatial resolution
have led to its wide use in studying the mean and turbu-
lent characteristics of fluid flows. With the development
of modern data processing software, the temporal resolu-
tion of LDA is mainly restricted by the concentration of
the seeding particles rather than the optics or software. In a
typical commercial use, a frequency range of 1KHz~10KHz
Figure 1. A typical view of the froth surface in a flotation
cell it is impossible to see through the froth
Figure 2. Schematic of the LDA
their applications are limited to transparent flows. Hot wire
probes (Hultmark, et al., 2011 Amini et al., 2013 2016a
2016b 2017 Amini and Xie 2020) have high spatial and
temporal resolution in turbulence quantification, but they
are susceptible to environmental factors. Conductivity
probes (Xu, Finch &Huls, 1992 Maldonado et al., 2008)
are techniques that can quantify turbulence in multiphase
flows, but their spatial resolutions are limited. Lagrangian
Particle Tracking (Kasagi and Matsunaga, 1995 La Porta,
Voth, Bodenschatz, 2001) can reveal particle trajectories
in multiphase flows, but are limited to transparent fluids
with weak index of refraction variations. Positron Emission
Particle Tracking (Guida et al., 2009 Chiti et al., 2011
Cole, et al., 2014, 2022, 2023 Mesa, et al., 2021) has been
used to quantify hydrodynamics. The main challenge is
how to determine the tracer location within dynamic multi-
phase flows (Cole, et al., 2022). Recent developments show
that PEPT can detect turbulent structures at macroscale
lengths by calculating the turbulent kinetic energy (TKE)
experienced by a PEPT tracer particle in a lab cell (Cole,
et al., 2023). Piezoelectric Vibration Sensors measure pres-
sure fluctuations and can determine velocity, acceleration,
strain, and force, which can be used to quantify turbulence
in multiphase flows (Bakker et al., 2009 Tabosa et al.,
2012 Meng et al. 2014a, 2014b, 2015, 2016). Electrical
Resistance Tomography (Meng et al., 2014, 2015 Xie et
al., 2016 Xie and Li, 2019 Xie 2021 2022) can measure
velocity fluctuation in multiphase flows, however, its tem-
poral and spatial resolutions need to be improved.
TURBULENCE MEASUREMENT
TECHNIQUES
Laser Doppler Anemometry (LDA)
Laser Doppler Anemometry (LDA), also called Laser
Doppler Velocimetry, utilizes the Doppler shift in a laser
beam to calculate the velocity of a transparent or semi-
transparent fluid seeded with tracing particles. In the early
1960s, the helium-neon laser was developed. The laser was
monochromatic, collimated, and coherent making it ideal
for researching fluid flow (Keating, 1988). The principle
of a LDA system is depicted in Figure 2. When entrained
particles pass through the fringes, laser light is reflected,
collected, and focused on a photo-detector. The fluctuating
frequency represents the magnitude of the particle’s veloc-
ity and its direction on the plane created by the two laser
beams. The LDA’s high temporal and spatial resolution
have led to its wide use in studying the mean and turbu-
lent characteristics of fluid flows. With the development
of modern data processing software, the temporal resolu-
tion of LDA is mainly restricted by the concentration of
the seeding particles rather than the optics or software. In a
typical commercial use, a frequency range of 1KHz~10KHz
Figure 1. A typical view of the froth surface in a flotation
cell it is impossible to see through the froth
Figure 2. Schematic of the LDA