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

6

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

7

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.

9

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

10

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