research project on applying doppler effect principles to...
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Research Project on Applying Doppler Effect Principles to Emergency Response of Nuclear Incidents
Executive Summary
During my internship I did at National Aerosol Facility at IIT Kanpur in Aug‐Sep 2019, I understood Doppler
effect in details, performed a lab experiment for a droplet coming out of an orifice to measure its velocity
under various pressures to understand Doppler effect and did a basic projectile range analysis. My
research topic was – Applying Doppler Effect Principles to Emergency Response of Nuclear Incidents.
The internship involved multiple visits of couple of days to IIT Kanpur. During first visit, I understood the
devices application and working principle.
During next visit, I conducted 4‐5 experiments at multiple flow rates of water and measured the water
velocity using the devices. I also analyzed to see how far the liquid droplets will go if injected as a
projectile. This experiment, although done at very low pressures and only on a droplet, can serve as proof
of concept for estimating high‐pressure nuclear reactor accidents and helps the scientists estimate on
how many villages near to the accident site need to be evacuated on immediate basis.
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Table of Contents
Understanding the Doppler Effect & its Usage 2‐4
Understanding Doppler Effect 2
Devices at Lab in IIT 2
o Monosize Droplet Generator MDG 2
o Phase Doppler Particle Analyzer (PDPA) 3
o Principle of Doppler Frequency Signal Generation 3
Experiments 4‐9
Trial Experiments on MDG 4
Doppler Effect Experiments 6
Outreach of droplet projectile range 8
o Basic Physics of Projectile Motion 8
o Analyzing Impact of Nuclear Incident 9
Conclusion and Way Forward 10
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A. Understanding the Doppler Effect & its Usage
Understanding Doppler Effect‐
Doppler Effect is the shift in frequency of light when there is relative motion between the source and
observer. It is used to measure the speed of a receding object. When the source is moving away from the
observer then the wave fronts have to travel a greater distance to reach the observer. As an example ,
when a star is moving away from the earth the wavelength in the middle of the visible region of the
spectrum moves towards the red end of the spectrum. As a result star looks more reddish when moves
away from the earth. This is known as red shift phenomenon. Similarly, when the waves are received from
a source moving towards the observer, there is an apparent decrease in wavelength. This is called blue
shift. The fractional change in frequency (Δν/ν) = (–vradial/c), Where vradial= component of the source
velocity along the line joining the observer to the source; c is velocity of light.
Devices at Lab in IIT:
Monosize Droplet Generator (MDG)‐
MDG produces droplets stream of uniform size for calibration of PDPA (Phase Doppler particle analyzer).
Many studies e.g. in nuclear reactors, atomization and many atmospheric as well as aerospace problem
statements require known uniform size drops and MDG is ideal device for these purposes.
MDG works on principle of applying periodic excitation to a reservoir, which is giving a laminar jet. When
periodic excitation is properly adjusted to resonant frequency, the jet breaks up into uniform drops. The
diameter of mono size droplets will also depends on discharge of water from syringe pump. Few
experiments has been done, shown in experiment section B of this report, to verify the relation of
excitation frequency, flow rate and outlet diameter.
D= /
Fig 1: Principle of MDG
Schematic diagram of MDG
a) Orifice b) Frequency generator c) Syringe pump Fig 2: Components of MDG
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Phase Doppler Particle Analyzer (PDPA)‐
Phase Doppler Particle Analyzer, measures the velocity of small particles, ranging from 0.5 μm to 500 μm,
that are moving in the field of interest. The physical principle used to measure the particle velocities is
scattering of light by the particle and Doppler Effect. Intersection of Laser, wavelength 561 nm each with
40MHz difference, has been used to obtain fringes, which is measuring volume for PDPA. The droplet will
pass through measuring volume. As a particle moves through the measuring volume, it scatters light. This
phenomenon results in a fluctuating pattern of scattered light intensity with a frequency proportional to
particle velocity. This scattered light will be collected by Receiver, which will further analyses frequency
shift in measuring volume as particle passes through it. The relation between frequency shift and velocity
is u=fD f
Principle of Doppler Frequency Signal Generation:
At the crossing point of two laser beams, an interference pattern is actually created by the coherence of
laser light source. This fringe pattern provides the necessary light pattern to illuminate the particles and
is reason behind creation of Doppler frequency signal.
The scattered light is collected and transmitted from Receiver to the photo multiple tubes through optical
fibers.
a) Laser controller b) Receiver
Fig 3: PDPA component
Fig 4: Fringe Pattern
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B. Experiments
Trial Experiments on MDG:
Experiments have been performed on MDG to observe the effect of frequency on generated droplet;
further droplets of MDG have been verified by photography method.
Flow rate(ml/hr) Frequency (KHz) Diameter (μm)
66 7.43 167
66 8.62 160
66 9.34 155
66 10.67 148
66 12.44 141
66 19.52 121
Fig 5: Schematic diagram of
experiment
Table1: Frequency and flow rate for the 50 μm orifice diameter
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Fig6: Droplet photography at 66 ml/hrs, 19.52 KHz for the 50 μm orifice diameter. Red Shows Diameter
of droplet and blue shows distance two two successive droplet center
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Doppler Effect Experiments –
I conducted five experiments with different flow rates to measure the velocity of water droplets. As flow
rate changes, pressure at mouth of orifice will change, which will impart force on generated droplet.
Because of forces, initial velocity of droplet will change. Pressure inside reservoirs can be calculated using
Bernoulli’s equation. We adjusted the Laser Doppler Velocimeter (LDV) and Receiver to get the right data
rate (number of valid data taken per second) and when it was achieved, we measured the velocity of
droplet. Details of experiments are below‐
1. At 81.25 ml/ hr flow‐
2. At 97.5 ml/hr flow
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3. At 113ml/hr flow
4. At 130 ml/hr flow
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5. At 145 ml/hr flow
The velocities and droplet diameters measured in these experiments are summarized in tables below‐
Flow rate ml/hr Diameter of droplet (micron)
Velocity of droplet (m/s)
RMS/sd of Velocity (m/s)
81.25 150.5 4.25 0.2533
97.5 147.6 5.17 0.3251
113 144.4 6.36 0.3317
130 136.6 7.86 0.4988
145 143.20 8.32 0.3519
Table 2: Velocity – Mean and Std Deviation (sd) of droplets
C. Outreach of velocity droplet projectile range –
Physics of Projectile Motion
Projectile motion is a form of motion where an object moves in a bilaterally symmetrical, parabolic
path. The path that the object follows is called its trajectory. Projectile motion only occurs when there
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is one force applied at the beginning on the trajectory, after which the only interference is from
gravity.
Range of Projectile‐
R=u2⋅sin2θ/ g
Moreover, the largest range will be experienced at a launch angle up to 45 degrees
Analyzing Impact of Nuclear Incident:‐
In our scenario, the range for various scenarios worked out by me is given below‐
Flow Rate ( ml/hr)
Velocity of Droplet m/s
Std Dev ofVelocity m/s
Range (u2 sin2 θ /g)
m
81.25 4.25 0.253 1.843
97.5 5.17 0.325 2.727
113 6.36 0.332 4.128
130 7.86 0.499 6.304
145 8.32 0.352 7.064
Table 3: Range of Area to be evacuated post nuclear incident.
This analysis is simple and assumes a 100‐micron crack and water droplet are behaving as an aerosol
of water – steam – radioactive elements. In reality, the scenario shall be very different and my analysis
can be further build up for studies at real conditions using a simulation software with aerosol analysis
capabilities to see impact of nuclear incident, decide the area to be defined as target area for low
population zone and plan for evacuation of low population area.
Fig 6: Picture depicting Emergency Plan Area
Emergency Plan Area
Plant Boundary
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D. Conclusion and Way Forward
Overall, my research at IIT was quite eventful. I got hands on opportunity to research and developed a
proof of concept. This concept if worked in details by working scientists can be helpful in understanding
the nuclear incident affected areas and can be handy in emergency response planning subsequent to a
nuclear incident.