The Effect of Frequency Excitation and Cavity Shape Changes on the Vortex Ring Formation of a Synthetic Jet Actuator

This paper provides an explanation of the effects of cavity shape and frequency excitation to the vortex formation of the synthetic jet. In order to get comprehensive results, this study will be conducted by both computational and experimental methods.The experiment method prepared by applying hotwire probe on the center point of the synthetic jet orifice, so from here the researcher get the Ux (average airflow velocity from membrane movement)in a low voltage signal, then the data will be transferred to analog data converter within the record speed 10.000 data/s. The cavities shapes that will be applied are half-sphere, tubes, and conical. The diameter varieties of the orifice are 3 mm, 5 mm and 8 mm. the simulation is started by utilizing the flow rate data from the experiment which can be put in the simulation boundary condition. Furthermore, from visual data of flow contour from CFD simulation the qualities vortex ring formation from SJA can be determined. Based on this research result, the formation of vortex ring occurs at the configuration B3, T3, T5, K3 and K5 of the SJA. Meanwhile, the other types of the synthetic jet cavity which have 8 mm of orifice diameter is not producing the vortex ring.

Active Flow Control; Ahmed Body; Airflow Separation; Drag Force ;Vortex Ring

Based on the findings from this research, it can be concluded that 10,000/s is the maximum jet speed generated by the SJA in the frequency range of 110 Hz–130 Hz with an uncertainty of 2% and a data amount of 10,000. The highest velocity jet is produced by K3 (conical cavity) with an orifice diameter of 3 mm. The average jet velocity generated reached 9.98 m/s. The vortex ring formation can be determined by the experiments and the CFD simulation method. Based on the experimental and simulation data, it can be concluded that the vortex ring formation equation calculation results were the same for both methods. Vortex ring formation can occur in B3, T3, T5, K3, and K5 synthetic jet cavities. A vortex ring is not formed on any type of cavity with an orifice diameter of 8 mm. In addition, determination of the occurrence of vortex ring formation can also be evaluated from the equation proposed by Utturkar (2002). The condition of  Re/S²> 1 is indicative for certain frequency excitations to produce a vortex ring. Thus, it can be said that the results from the simulation and experiments conducted in the present study provide some evidence to support the theory of vortex ring formation mentioned by some previous researchers.

Ahmed, S., Ramm, G., Faltin, G., 1984. Some Salient Features of the Time-averaged Ground Vehicle Wake. SAE Technical Paper 840300, 1984, https://doi.org/10.4271/840300

Bruneau, C.-H., Creuse, E., Depeyras, D., Gillieron, P., Mortazavi, I., 2011. Active Procedures to Control the Flow Past the Ahmed Body with a 25° Rear Window. International Journal Aerodynamics, Volume 1(3/4), pp. 299–317

Conan, B., Anthoine, J., Planquart, P., 2011. Experimental Aerodynamic Study of a Car-type Bluff Body. Experiments in Fluids, Volume 50(5), pp. 1273–1284

Fares, E., 2006. Unsteady Flow Simulation of the Ahmed Reference Body using a Lattice Boltzmann Approach. Computers and Fluids, Volume 35(8–9), pp. 940–950

Gak-El-Hak, M., 1996. Modern Development in Flow Control. Applied Mechanics Reviews, Volume 49(7), pp. 365–379

Glezer, A., 1998. The Formation of Vortex Rings. Physics of Fluids, Volume 31(12), pp. 3532–3542

Hintenberger C., García-Villalba, M., Rodi, W., 2004. Large Eddy Simulation of Flow around the Ahmed Body. The Aerodynamics of Heavy Vechicles: Truck, Buses, and Trains, Volume 19, pp. 77–87

Holman, R., Utturkar, Y., Mittal, R., Smith, B.L., Cattafesta, L., 2005. Formation Criterion for Synthetic Jets. AIAA Journal, Volume 43(10), pp. 2110–2116

Hucho W.H., 1998. Aerodynamics of Road Vehicle. Annual Review of Fluid Mechanics, Volume 25, pp. 285–537

Hucho, W.H., 2002. Aerodynamik der stumpfer K’’orper – Physikalische Grundlagen und Anwendung in der Praxis (Aerodynamics of Dull K''Orpers - Physical Principles and Application in Practice)

Intergovernmental Group of Experts, 2001. Les Elements Scientifique, 3èmerapport èvaluation 2001 (Scientific Elements, Third Assessment Report 2001). s.l., Available online at http:/ www.grida.no/climate/ippcc_tar International Energy Agency World Energy Outlook, 2007. Executive Summary, China and India Insights, International Energy Agency IEA. s.l., ISBN: 978-92-64-02730-5

Kourta, A., Gillieron, P., 2009. Impact of the Automotive Aerodynamic Control on the Economic Issues. Journal of Applied Fluid Mechanics, Volume 2(2), pp. 69–75

Minguez M., Pasquetti, R., Serre, E., 2008. High-order Large Eddy Simulation of Flow over the “Ahmed Body” Car Model. Physics of Fluids, Volume 20(9), https://doi.org/10.1063/1.2952595

Roumeas M., Gilieron, P., Kuorta, A., 2009. Analysis and Control of Near Wake Flow over a Square Back Geometry. Computers & Fluids, Volume 38(1), pp. 60–70

Roumeas M., Gilieron, P., Kuorta, A., 2009. Drag Reduction by Flow Separation Control on a Car after Body. International Journal for Numerical Method in Fluid, Volume 60(11), pp. 1222–1240

Smith, B., Glezer, A., 1998. The Formation and Evolution of Synthetic Jets. Physics of Fluids, Volume 10(9), pp. 2281–2297

Smith, B.L., Swift, G.W., 2001. Synthetic Jets at Large Reynolds Number and Comparison to Continuous Jets. In: AIAA Computational Fluid Dynamics Conference

Uruba, V., 2009. On the Ahmed Body Wake. Issue Colloquium Fluid Dynamics, Institute of Thermomechanics AS CR, v.v.i., Prague

Utturkar, Y., 2002. Numerical Investigation of Synthetic Jet Flow Fields. Florida: Department of Mechanical Engineering, University of Florida