Experimental study of velocity components of low-RE pulsatile flow through bare rod bundle

Highlights: • Pulsatile flow through rod bundles was investigated. • The axial and lateral velocities in a cycle were analyzed. • The accelerating and decelerating half-cycles are different. • Lateral velocity in pulsatile flow is lower than in steady flow. • Turbulence intensifies with increase in the mean velocity. - Abstract: The possibility of unsteady flow through rod bundles is currently gaining attention from researchers. Velocity components of pulsatile flow (time-averaged Reynolds number = 0.7–4.0 × 10³) through 5 × 5 square array bare rod bundles (P/D = 1.326 and W/D = 1.268) has been investigated experimentally. The responses of axial and lateral velocities to the sinusoidal imposed pulsation were different. The axial velocity responded directly to the imposed pulsation while the lateral velocity diminished. Also, the response in the subchannels and gaps was different. The axial velocity in the gaps followed the imposed trend, while at the subchannel, the acceleration was steep but the deceleration steady. Lateral velocity in the gaps and subchannels differs by an average of 40%. Turbulence was higher on the rod surfaces compare to other points. The dissimilarity in the acceleration and deceleration half-cycles suggests that there is a difference in the instantaneous parameters during acceleration and deceleration. Further in situ measurements of the pressure field is a potential follow-up study.