The behavior of spiral flow structures along the trailing edges of the E-block arm has been investigated under increasing airflow velocities. These coherent structures in the flow are commonly believed to be closely associated with the flow induced vibrations on the E-block arms. A model of the HDD has been shown in Fig. 1. The experiments showed that vortex shedding is detected in a HDD model when the motor speed is as low as 1200rpm. A turbulent wake is formed immediately after flow over the E-block arms, as shown in Fig. 2. Flow turbulence in the wake becomes significant from 7200rpm onwards and peaked at 10,000rpm, as illustrated in Fig. 3. From 12,000rpm onwards, a turbulent jet is formed instead of a turbulent wake. The flow regime change deserved further in depth investigations in order to understand the flow physics so that future designs of HDD that run at even higher rotational speeds with acceptable TMR could be realizable.
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