Determination of HGA aerodynamic indicial responses for unsteady flow computation Somprasong Saowjoo King Mongkut’s University of Technology Thonburi Mechanical Engineering Department Somprasong Saowjoo 1*, Wasawat Saowadee 2, Chawin Chantharasenawong 3 and Wishsanuruk Wechsatol 4

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 3

Determination of HGA aerodynamic indicial responses for unsteady flow computation 4 Top : Ф C Center : Ф I Bottom : Response

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

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 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 x Chord Length 9 x Chord Length

Determination of HGA aerodynamic indicial responses for unsteady flow computation The static lift curves for each section Section No.5 Section No.2 Low Pressure 11

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 12 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.1Section No.2 13

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 14 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 15

Determination of HGA aerodynamic indicial responses for unsteady flow computation Conclution 16 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 * 17

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