Determination of HGA aerodynamic indicial responses for unsteady flow computation
Somprasong Saowjoo
King Mongkut’s University of Technology ThonburiMechanical Engineering Department
Determination of HGA aerodynamic indicial responses for unsteady flow computationSomprasong Saowjoo1*, Wasawat Saowadee2, Chawin Chantharasenawong3 and Wishsanuruk Wechsatol4
Determination of HGA aerodynamic indicial responses for unsteady flow computation
- Determine the empirical aerodynamic response coefficients of the HGA
- Determine the dynamic aerodynamic forces acting on the HGA
Objective
2
Determination of HGA aerodynamic indicial responses for unsteady flow computation
To study the aerodynamic loads, the indicial force response to a step change in angle of incidence is given by
MtMCMtM
tC CSL
IL ,,4
3
Determination of HGA aerodynamic indicial responses for unsteady flow computation
4
MtMCMtM
tC CSL
IL ,,4
Top : ФC
Center : ФI
Bottom : Response
2 21 1 2 2 1 2 1 2
1 2 1 2
2 21 1 2 2
2 21 exp exp , , ,
exp ( , , , )0.75
(1 ) ( )
C
I
I
V VA b t A b t f A A b b
c c
tf A A b b
TM M Ab A b
1
2
Determination of HGA aerodynamic indicial responses for unsteady flow computation
The indicial function from step input are given by
The coefficients A1, A2, b1 and b2 are the cross-section shape dependent parameters.
5
The model used in the calculation is a typical HGA of a 3.5-inch harddisk drive and divided into 9 parts (10 stations)
Determination of HGA aerodynamic indicial responses for unsteady flow computation
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Determination of HGA aerodynamic indicial responses for unsteady flow computation
In order to get valid transient analysis results, the model needs to be verified. Modal analysis has been conducted for NACA0012 with reasonable success and the same method can be used with HGA with confidence*
Wasawat Saowadee , Somprasong Saowjoo, Chawin Chantharasenawong. Determination of aerofoil aerodynamic indicial response function coefficients using CFD simulation data. Department of Mechanical Engineering, King Mongkut’s University of Technology Thonburi.
*
NACA0012 Aerofoil HGA model
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Determination of HGA aerodynamic indicial responses for unsteady flow computation
Lift Coefficient vs Angle of Attack
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0 1 2 3 4 5 6
Angle of Attack [degree]
Lif
t C
oef
fici
ent
0.001.00
2.003.00
4.005.00
6.007.00
8.00
Err
or
[%]
COMSOL
XFOIL
Error
In previous research, we compared the static solutions of the NACA0012 aerofoil with those found using the software XFOIL* and the error was below 4%.
Mark Drela. Subsonic Airfoil Development System, XFOIL, Massachusetts Institute of Technology (MIT).* 8
Determination of HGA aerodynamic indicial responses for unsteady flow computation
The four coefficients are then optimized in order to minimize the difference between the two curves which is computed using the root-mean-square.
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The range of Reynold’s number and Mach number on a HGA are the same values as those found in the real harddisk drive at normal operating conditions.
Determination of HGA aerodynamic indicial responses for unsteady flow computation
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13.5 x Chord Length
9 x
Ch
ord
Le
ng
th
Determination of HGA aerodynamic indicial responses for unsteady flow computation
The static lift curves for each section
Section No.5Section No.2
Low Pressure
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The results are verified by comparing them to static CFD results and the error is approximately 0.3%.
Determination of HGA aerodynamic indicial responses for unsteady flow computation
The dynamic lift simulation results
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Section No.5
Section No.2
Determination of HGA aerodynamic indicial responses for unsteady flow computation
Indicial responses computed by COMSOL and the best fit curves for the LBM are plotted together
Section No.1 Section No.2
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NACA0012 Airfoil
HGA cross section no.2
HGA cross section no.6
Determination of HGA aerodynamic indicial responses for unsteady flow computation
The values of LBM coefficients for each HGA section
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Blunt Body
Streamlined Body
Determination of HGA aerodynamic indicial responses for unsteady flow computation
Finally, the total lift force of the HGA can be determined from the strip theory, where
WingAreauCLn
iLitotal
2
10
2
1
15
Determination of HGA aerodynamic indicial responses for unsteady flow computation
Conclution
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Wind tunnel testing CFD
This work has proposed a new way :
High cost of equipment
Taking more time to analyze
Economical in financial terms
Few computing resource
Spend less time
NEW WAY
Determination of HGA aerodynamic indicial responses for unsteady flow computation
Further work should include modification of these functions so that they are more appropriate for blunt bodies.
Aerofoil model
HGA model
* Leishman J.G. and Beddoes T.S.A Generalised Model for Airfoil unsteady Aero dynamic Behaviour and Dynamic stall using the Indical Method. Proceeding of the 42nd Annual forum of the American Helicopter Society Washington DC, 1968
*
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Thank you for your attention
Questions ?
Determination of HGA aerodynamic indicial responses for unsteady flow computation
Special Thanks• National Science and Technology Development Agency (NSTDA)• National Electronics and Computer Technology Center (NECTEC)• The Hard Disk Drive Institute (HDDI)• Industry/University Cooperative Research Center (I/U CRC)• Western Digital (Thailand) Co., Ltd.• Assoc.Prof.Dr.Surachate Chutima