This numerical investigation studied the effect of Reynolds number and pitch ratio on the lock-in ability of an aeroacoustic field in ducted flows. The study found that:
- The onset of aeroacoustic resonance depended on both the Reynolds number and the pitch ratio of the cylinders. Higher Reynolds numbers and smaller pitch ratios increased the likelihood of resonance.
- For a two cylinder configuration, resonance only occurred above a Reynolds number of 27,000.
- For a four cylinder configuration, resonance was more likely at smaller pitch ratios and higher Reynolds numbers.
- A multiple cylinder array only exhibited resonance under conditions of high Reynolds number and small pitch ratio that produced coherent vortex shedding matching the acoustic frequency
An Investigation on the Performance Characteristics of a Centrifugal CompressorIJERD Editor
The design and off-design performance characteristics of single stage centrifugal compressor
consisting of 12 vanes impeller interfacing with 11 vanes diffuser have been studied experimentally and
numerically. The impeller has been designed and developed with radial exit, 30o inlet blade angle (with
tangent), 77 mm diameter and the discharge volute considering constant mean flow velocity. The performance
of the compressor at varying capacity (60 to 120 % of design) by controlling the discharge valve and with the
variation of rotating speed (15000 to 35000 rpm) by regulating speed of the coupled gas turbine has been
conducted at the recently developed test rig. The numerical simulation has been done by adopting viscous
Reynolds Average Navier-Stokes (RANS) equations with and without Coriolis Force & Centrifugal Force in
rotating reference frame (impeller) and stationary reference frame (casing) respectively utilizing CFD software
Fluent 14. The flow around a single vane of impeller interfacing with single vane of diffuser, the rotational
periodicity and sliding mesh at the interfacing zone between rotating impeller and stationery diffuser are
considered. Non dimensional performance curves derived from experimental and numerical results are
presented and compared. The numerical results are found to match very closely with the experimented data near
the design point and deviation is observed at the both side of the designed operating point. Non-uniform
pressure profiles towards the impeller exit and strong cross flow from blade to blade are detected at low flow
operating conditions. Total pressure, static pressure and velocity distributions at design and off design
operation obtained from the CFD results are analysed and presented here.
Experimental Studies, Geometry Acquisition and Grid Generation Of Diesel Engi...meijjournal
A typical diesel engine port is of complicated geometry . This paper addresses the experimental studies of
intake port of a four cylinder diesel engine for different vacuum pressures and valve lift positions. In this
study the cylinder head is experimented through a paddle wheel flow setup which gives the flow coefficient
and swirl number as output. The main scope of the work is to understand the flow behaviour through the
intake port and finally to determine mean flow coefficient and mean swirl number for different valve lift
ratios L/D, where L is valve lift and D is bore diameter. This paper also addresses the geometry acquisition
and grid generation for three dimensional Computational Fluid Analysis for flow filed computation and
obtain a calibrated CFD code for future design once the code is validated with experimental results
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
An Investigation on the Performance Characteristics of a Centrifugal CompressorIJERD Editor
The design and off-design performance characteristics of single stage centrifugal compressor
consisting of 12 vanes impeller interfacing with 11 vanes diffuser have been studied experimentally and
numerically. The impeller has been designed and developed with radial exit, 30o inlet blade angle (with
tangent), 77 mm diameter and the discharge volute considering constant mean flow velocity. The performance
of the compressor at varying capacity (60 to 120 % of design) by controlling the discharge valve and with the
variation of rotating speed (15000 to 35000 rpm) by regulating speed of the coupled gas turbine has been
conducted at the recently developed test rig. The numerical simulation has been done by adopting viscous
Reynolds Average Navier-Stokes (RANS) equations with and without Coriolis Force & Centrifugal Force in
rotating reference frame (impeller) and stationary reference frame (casing) respectively utilizing CFD software
Fluent 14. The flow around a single vane of impeller interfacing with single vane of diffuser, the rotational
periodicity and sliding mesh at the interfacing zone between rotating impeller and stationery diffuser are
considered. Non dimensional performance curves derived from experimental and numerical results are
presented and compared. The numerical results are found to match very closely with the experimented data near
the design point and deviation is observed at the both side of the designed operating point. Non-uniform
pressure profiles towards the impeller exit and strong cross flow from blade to blade are detected at low flow
operating conditions. Total pressure, static pressure and velocity distributions at design and off design
operation obtained from the CFD results are analysed and presented here.
Experimental Studies, Geometry Acquisition and Grid Generation Of Diesel Engi...meijjournal
A typical diesel engine port is of complicated geometry . This paper addresses the experimental studies of
intake port of a four cylinder diesel engine for different vacuum pressures and valve lift positions. In this
study the cylinder head is experimented through a paddle wheel flow setup which gives the flow coefficient
and swirl number as output. The main scope of the work is to understand the flow behaviour through the
intake port and finally to determine mean flow coefficient and mean swirl number for different valve lift
ratios L/D, where L is valve lift and D is bore diameter. This paper also addresses the geometry acquisition
and grid generation for three dimensional Computational Fluid Analysis for flow filed computation and
obtain a calibrated CFD code for future design once the code is validated with experimental results
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
This is a self-contained three-day short course on the fundamentals of tactical missile design. It provides a system-level, integrated method for missile aerodynamic configuration/propulsion design and analysis and addresses the broad range of alternatives in meeting cost and performance requirements. The methods presented are generally simple closed-form analytical expressions that are physics-based, to provide insight into the primary driving parameters. Configuration sizing examples are presented for rocket-powered, ramjet-powered, and turbojet-powered baseline missiles. Typical values of missile parameters and the characteristics of current operational missiles are discussed, as well as the enabling subsystems and technologies for tactical missiles, the development process, and the current/projected state-of-the-art. The attendees will vote on the relative emphasis of the topics. Over thirty videos illustrate missile development activities and missile performance. Finally, each attendee may design, build, and fly an air-powered rocket that illustrates some of the course design methods.
Aerodynamics Part II of 3 describes aerodynamics of bodies in supersonic flight.
For comments please contact me at solo.hermelin@gmail.com.
For more presentations on different subjects visit my website at http://www.solohermelin.com.
ELECTRIC CIRCUITS IMETRIC PREFIX TABLEMetricPrefixSymb.docxrobert345678
ELECTRIC CIRCUITS I
METRIC PREFIX TABLE
Metric
Prefix
Symbol
Multiplier
(Traditional Notation)
Expo-
nential
Description
Yotta
Y
1,000,000,000,000,000,000,000,000
1024
Septillion
Zetta
Z
1,000,000,000,000,000,000,000
1021
Sextillion
Exa
E
1,000,000,000,000,000,000
1018
Quintillion
Peta
P
1,000,000,000,000,000
1015
Quadrillion
Tera
T
1,000,000,000,000
1012
Trillion
Giga
G
1,000,000,000
109
Billion
Mega
M
1,000,000
106
Million
kilo
k
1,000
103
Thousand
hecto
h
100
102
Hundred
deca
da
10
101
Ten
Base
b
1
100
One
deci
d
1/10
10-1
Tenth
centi
c
1/100
10-2
Hundredth
milli
m
1/1,000
10-3
Thousandth
micro
µ
1/1,000,000
10-6
Millionth
nano
n
1/1,000,000,000
10-9
Billionth
pico
p
1/1,000,000,000,000
10-12
Trillionth
femto
f
1/1,000,000,000,000,000
10-15
Quadrillionth
atto
a
1/1,000,000,000,000,000,000
10-18
Quintillionth
zepto
z
1/1,000,000,000,000,000,000,000
10-21
Sextillionth
yocto
y
1/1,000,000,000,000,000,000,000,000
10-24
Septillionth
4-BAND RESISTOR COLOR CODE TABLE
BAND
COLOR
DIGIT
Band 1: 1st Digit
Band 2: 2nd Digit
Band 3: Multiplier
(# of zeros
following 2nd digit)
Black
0
Brown
1
Red
2
Orange
3
Yellow
4
Green
5
Blue
6
Violet
7
Gray
8
White
9
Band 4: Tolerance
Gold
± 5%
SILVER
± 10%
5-BAND RESISTOR COLOR CODE TABLE
BAND
COLOR
DIGIT
Band 1: 1st Digit
Band 2: 2nd Digit
Band 3: 3rd Digit
Band 4: Multiplier
(# of zeros
following 3rd digit)
Black
0
Brown
1
Red
2
Orange
3
Yellow
4
Green
5
Blue
6
Violet
7
Gray
8
White
9
Gold
0.1
SILVER
0.01
Band 5: Tolerance
Gold
± 5%
SILVER
± 10%
EET Formulas & Tables Sheet
Page
1 of
21
UNIT 1: FUNDAMENTAL CIRCUITS
CHARGE
Where:
Q = Charge in Coulombs (C)
Note:
1 C = Total charge possessed by 6.25x1018 electrons
VOLTAGE
Where:
V = Voltage in Volts (V)
W = Energy in Joules (J)
Q = Charge in Coulombs (C)
CURRENT
Where:
I = Current in Amperes (A)
Q = Charge in Coulombs (C)
t = Time in seconds (s)
OHM’S LAW
Where:
I = Current in Amperes (A)
V = Voltage in Volts (V)
R = Resistance in Ohms (Ω)
RESISTIVITY
Where:
ρ = Resistivity in Circular Mil – Ohm per Foot (CM-Ω/ft)
A = Cross-sectional area in Circular Mils (CM)
R = Resistance in Ohms (Ω)
ɭ = Length in Feet (ft)
Note:
CM: Area of a wire with a 0.001 inch (1 mil) diameter
CONDUCTANCE
Where:
G = Conductance in Siemens (S)
R = Resistance in Ohms (Ω)
CROSS-SECTIONAL AREA
Where:
A = Cross-sectional area in Circular Mils (CM)
d = Diameter in thousandths of an inch (mils)
ENERGY
Where:
W = Energy in Joules (J). Symbol
is an italic
W.
P = Power in Watts (W). Unit
is not an italic W.
t = Time in seconds (s)
Note:
1 W = Amount of power when 1 J of energy
is used in 1 s
POWER
Where:
P = Power in Watts (W)
V
= Voltage in Volts (V)
I = Current in Amperes (A)
Note.
Noise Reduction Modelling Study for Aircraft Cavity - Chun C GanGan Chun Chet
Modelling (Aircraft) Air Flow Across Rectangular Cavity, reduction in noise amplitude, postulating higher boundary layer frequency (efficient noise to signal ratio)
This is a self-contained three-day short course on the fundamentals of tactical missile design. It provides a system-level, integrated method for missile aerodynamic configuration/propulsion design and analysis and addresses the broad range of alternatives in meeting cost and performance requirements. The methods presented are generally simple closed-form analytical expressions that are physics-based, to provide insight into the primary driving parameters. Configuration sizing examples are presented for rocket-powered, ramjet-powered, and turbojet-powered baseline missiles. Typical values of missile parameters and the characteristics of current operational missiles are discussed, as well as the enabling subsystems and technologies for tactical missiles, the development process, and the current/projected state-of-the-art. The attendees will vote on the relative emphasis of the topics. Over thirty videos illustrate missile development activities and missile performance. Finally, each attendee may design, build, and fly an air-powered rocket that illustrates some of the course design methods.
Aerodynamics Part II of 3 describes aerodynamics of bodies in supersonic flight.
For comments please contact me at solo.hermelin@gmail.com.
For more presentations on different subjects visit my website at http://www.solohermelin.com.
ELECTRIC CIRCUITS IMETRIC PREFIX TABLEMetricPrefixSymb.docxrobert345678
ELECTRIC CIRCUITS I
METRIC PREFIX TABLE
Metric
Prefix
Symbol
Multiplier
(Traditional Notation)
Expo-
nential
Description
Yotta
Y
1,000,000,000,000,000,000,000,000
1024
Septillion
Zetta
Z
1,000,000,000,000,000,000,000
1021
Sextillion
Exa
E
1,000,000,000,000,000,000
1018
Quintillion
Peta
P
1,000,000,000,000,000
1015
Quadrillion
Tera
T
1,000,000,000,000
1012
Trillion
Giga
G
1,000,000,000
109
Billion
Mega
M
1,000,000
106
Million
kilo
k
1,000
103
Thousand
hecto
h
100
102
Hundred
deca
da
10
101
Ten
Base
b
1
100
One
deci
d
1/10
10-1
Tenth
centi
c
1/100
10-2
Hundredth
milli
m
1/1,000
10-3
Thousandth
micro
µ
1/1,000,000
10-6
Millionth
nano
n
1/1,000,000,000
10-9
Billionth
pico
p
1/1,000,000,000,000
10-12
Trillionth
femto
f
1/1,000,000,000,000,000
10-15
Quadrillionth
atto
a
1/1,000,000,000,000,000,000
10-18
Quintillionth
zepto
z
1/1,000,000,000,000,000,000,000
10-21
Sextillionth
yocto
y
1/1,000,000,000,000,000,000,000,000
10-24
Septillionth
4-BAND RESISTOR COLOR CODE TABLE
BAND
COLOR
DIGIT
Band 1: 1st Digit
Band 2: 2nd Digit
Band 3: Multiplier
(# of zeros
following 2nd digit)
Black
0
Brown
1
Red
2
Orange
3
Yellow
4
Green
5
Blue
6
Violet
7
Gray
8
White
9
Band 4: Tolerance
Gold
± 5%
SILVER
± 10%
5-BAND RESISTOR COLOR CODE TABLE
BAND
COLOR
DIGIT
Band 1: 1st Digit
Band 2: 2nd Digit
Band 3: 3rd Digit
Band 4: Multiplier
(# of zeros
following 3rd digit)
Black
0
Brown
1
Red
2
Orange
3
Yellow
4
Green
5
Blue
6
Violet
7
Gray
8
White
9
Gold
0.1
SILVER
0.01
Band 5: Tolerance
Gold
± 5%
SILVER
± 10%
EET Formulas & Tables Sheet
Page
1 of
21
UNIT 1: FUNDAMENTAL CIRCUITS
CHARGE
Where:
Q = Charge in Coulombs (C)
Note:
1 C = Total charge possessed by 6.25x1018 electrons
VOLTAGE
Where:
V = Voltage in Volts (V)
W = Energy in Joules (J)
Q = Charge in Coulombs (C)
CURRENT
Where:
I = Current in Amperes (A)
Q = Charge in Coulombs (C)
t = Time in seconds (s)
OHM’S LAW
Where:
I = Current in Amperes (A)
V = Voltage in Volts (V)
R = Resistance in Ohms (Ω)
RESISTIVITY
Where:
ρ = Resistivity in Circular Mil – Ohm per Foot (CM-Ω/ft)
A = Cross-sectional area in Circular Mils (CM)
R = Resistance in Ohms (Ω)
ɭ = Length in Feet (ft)
Note:
CM: Area of a wire with a 0.001 inch (1 mil) diameter
CONDUCTANCE
Where:
G = Conductance in Siemens (S)
R = Resistance in Ohms (Ω)
CROSS-SECTIONAL AREA
Where:
A = Cross-sectional area in Circular Mils (CM)
d = Diameter in thousandths of an inch (mils)
ENERGY
Where:
W = Energy in Joules (J). Symbol
is an italic
W.
P = Power in Watts (W). Unit
is not an italic W.
t = Time in seconds (s)
Note:
1 W = Amount of power when 1 J of energy
is used in 1 s
POWER
Where:
P = Power in Watts (W)
V
= Voltage in Volts (V)
I = Current in Amperes (A)
Note.
Noise Reduction Modelling Study for Aircraft Cavity - Chun C GanGan Chun Chet
Modelling (Aircraft) Air Flow Across Rectangular Cavity, reduction in noise amplitude, postulating higher boundary layer frequency (efficient noise to signal ratio)
This PowerPoint describes briefly about the ultrasonic absorption technique. I briefly discussed the various techniques and theoretical concepts involved in the absorption technique.
Similar to Numerical Investigation of the Reynolds Number and Pitch Ratio Effect on the Lock-In Ability of an Aero-Acoustic Field in Ducted flows". (20)
Numerical Investigation of the Reynolds Number and Pitch Ratio Effect on the Lock-In Ability of an Aero-Acoustic Field in Ducted flows".
1. Numerical Investigation of Reynolds
Number and Pitch Ratio Effect on
Lock-in Ability
of an Aeroacoustic Field in Ducted
Flows
Dept. of Mechanical and Manufacturing Engineering
Trinity College Dublin
Cristina Paduano
2. Aeroacoustic Resonance of Bluff Bodies in Ducted Flows
Noise intensification
It can occur when a Gas Flow in a duct/cavity exhibits Periodic Vortices
Vortex shedding Duct acoustic mode
𝒇 𝒗 𝒇 𝒂
HYDRODYNAMIC
Vortex shedding at
acoustic frequency
𝒇 𝒗 = 𝒇 𝒂
Tonal noise
is emitted
Vortexsheddingfrequency
LOCK-IN
Flow velocity
flow
𝒇 𝒂 𝒅𝒖𝒄𝒕
Off
resonance
Off
resonance
NOISE
SELF-SUSTAINS and
ENHANCES
3. Aeroacoustic Resonance Behaviour of Tube Array
10 15 20 25 30
0
500
1000
1500
2000
V
(m/s)
Pa(Pa)
10 15 20 25 30
0
100
200
300
400
500
V
(m/s)
Frequency(Hz)
Pressure measurements (heat exchanger)
UNPREDICTABLE VELOCITY
EXTENTS OF LOCK IN RANGE UNKNOWN
Velocity measurements (heat exchanger)
140 dB
(images from Finnegan -2011)
“Tube array resonance occurs when the
energy available in the flow(dynamic head)
overcomes the acoustic damping of the
system” - (Feenstra et al.- 2006)
4. Conditions for Resonance
(Hall, Ziada, Weaver data -2003)
Lock-in map (EXPERIMENTAL DATA)
Conditionsforresonance
Amplitude of the
acoustic wave
Frequency ratio
This research:
Reynolds number and Pitch ratio
• To understand aeroacoustic resonance in
tube array it is necessary to understand
the strength of the sound sources formed
around the tubes.
• Numerous experimental study for
reduced array configuration (single -2- 4
cylinders) used a fixed width test section (
1 fa) and varied fv.
5. Research Motivations and Objectives
• Mechanism of lock in is not yet clear
• Effect of turbulence increasing and
variation of the vortices patterns were
indicated as possible parameters
contributing to resonance of tube array
(Fitzpatrick -1980, Ziada-1989).
However many experiments focused
more on variation of frequency ratio.
Is there a flow characteristic which causes Lock
in to occur ?
Does the aeroacoustic resonance of 2 and 4
cylinders configuration represent the
aeroacustic resonance of tube array ?
Vortexsheddingfrequency
Flow velocity
𝒇 𝒂
𝒇 𝒗
=1
Vortices
incoherent
structure
Coherent
acoustic
sources Vortices
incoherent
structure
LOCK IN
FLOW
STRUCTURE
6. CFD Simulation of Aeroacoustic Resonance
ACOUSTICS
IS
“ COMPRESSIBLE”
INCOMPRESSIBLE
FLOW
(uRANS, SST) += OSCILLATING VELOCITY
(BOUNDARY CONDITION)
Hydrodynamic Analogy (Tan ,Thompson, Hourigan-2003)
TRASVERSAL ACOUSTIC WAVE replaced by the Flow OSCILLATION which it causes
RESONANCE: 𝑓𝑎 chosen to be in LOCK-IN ratio with 𝑓𝑣
𝑼 𝒂𝒄𝒔=Asin(2 𝑓𝑎t)
7. Application
Two cylinders in tandem
Four cylinders in square
In line multiple cylinder array
Vortexsheddingfrequency
Flow velocity
𝒇 𝒂
𝒇 𝒗
=1
Pre-coinc.
resonance
Coinc.
resonance
IMPOSED LOCK IN CONDITION
FLOWSTRUCTUREVARIATION TURBULENCE EFFECT
Mean flow velocity variation applied (i.e. RE
variation 10000-36000)
VORTICES CONVECTIVE VEL. VARIATION
Variation of vortices convective velocity is
obtained by varying the pitch ratio L/D 2.5-3.
(Configuration analysed – Re and pitch as Finnegan-2011)
9. LOCK-IN and Velocity contours
% V inlet
Normalized velocity
WITHOUT EXCITATION
% V inlet
Normalized velocity
case NOT LOCKED IN (Re=10000)
Normalized velocity
case LOCKED IN (Re=36000)
Normalized velocity
WITHOUT EXCITATION
% V inlet% V inlet
10. EXPERIMENTAL ACOUSTIC POWER
Acoustic Power
NUMERICAL ACOUSTIC POWER
(Finnegan, Meskell and Ziada data-2010)
PreCoincidence 𝑓𝑣 < 𝑓𝑎
Coincidence 𝑓𝑣 > 𝑓𝑎
Sinks (Flow takes energy from acoustics)
Sources (Flow puts energy into acoustics)
PreCoincidence 𝑓𝑣 < 𝑓𝑎
Coincidence 𝑓𝑣 > 𝑓𝑎
11. Four Cylinder Resonance - Summary of Results
Coincidence 𝑓𝑎 /𝑓𝑣 =0.85
PICTH 2.5
• Lock in only occurring at
Coincidence and for all Reynolds
numbers
PICTH 3
• Lock in only occurring at
Coincidence ONLY at the higher
Reynolds number
Pressure,Pascals
Coincidence 𝑅𝑒 36000 (𝑃𝑖𝑐𝑡ℎ 2.5) (Finnegan, Meskell and Ziada data-2010)
12. Multiple Cylinder Array Resonance - Summary of Results
Coincidence 𝑓𝑎 /𝑓𝑣 =0.85 –Pitch L/D 2.5 PICTH 2.5
• Lock in only occurring at
Coincidence and for all Reynolds
numbers
PICTH 3
• Lock in NEVER OCCURRING
(Finnegan, Meskell and Ziada data-2010)
Coincidence 𝑅𝑒 36000 (𝑃𝑖𝑐𝑡ℎ 2.5)
13. Conclusions
The cylinder configurations analysed have
shown a different resonance response to
the similar lock in excitation;
The onset of resonance appeared to be
influenced by the Reynolds number
(Two cylinders case) and influenced by
the variation of the cylinders Pitch ratio
(Four cylinders case);
The frequency ratio could not be the only
parameter instigating acoustic resonance,
the flow condition (i.e. Turbulence and
Vortices Convective Velocity) should be
considered as well.
RE Pre-Coinc. Coinc.
Two
Cylinders
(L/D 2.5)
12000
36000
No resonance
Resonance
No resonance
Resonance
Four
Cylinders
(L/D 2.5)
12000
36000
No resonance
No resonance
Resonance
Resonance
Four
Cylinders
(L/D 3)
12000
36000
No resonance
No resonance
No resonance
Resonance
Array
(L/D 2.5)
12000
36000
No resonance
No resonance
Resonance
Resonance
Array
(L/D 3)
12000
36000
No resonance
No resonance
No resonance
No resonance