**Article details**

**Title: **Rotational Vortex Rope Detection using Recurrence Plot Analysis

**Author(s): ***Angela Digulescu* *Teodor Petruţ* *Ion Candel* *Cornel Ioana* *Florentina Bunea* *Georgiana Dunca* *Diana-Maria Bucur* *Alexandru ÅžerbÄƒnescu*

**Abstract: **In this paper, a new approach is proposed for the assessment of a vortex in fluid flow using an active acoustic system. The experiment is done on a reduced scale experimental pipe with ultrasonic transceivers. The purpose of the paper is to point out the presence of cavitation appearing in this pipe using wide band signals in the active acoustic system mode. Therefore, the Recurrence Plot Analysis (RPA) method which constitutes an interesting tool for the characterization of a dynamical system is used in terms of signal processing. The investigation is done varying the flow from steady flow to cavitation flow and backwards.

**Keywords: **non-intrusive monitoring, recurrence plot analysis, phase space.

** References: **

[1] N. TAKAHASHI, T. MIYAZAKI - *The Influence of Turbulence on a Columnar Vortex with Axial Flow*, Proc. in Applied Mathematics and Mechanics, PAMM, pp. 879-882, Berlin, Germany, Mar. 27-31, 2006

[2] K.A. EMANUEL - *A Note on the Stability of Columnar Vortices*, Journal of Fluid Mechanics, Vol. 145, pp. 235-238, Aug. 1984

[3] W.L. RUBIN – *Radar-Acoustic Detection of Aircraft Wake Vortices*, Journal of Atmospheric and Oceanic Technology, Vol. 17, pp. 1058-1065, 2000

[4] N. MARWAN, S. SCHINKEL, J. KURTHS – *Recurrence Plots 25 Years Later – Gaining Confidence in Dynamic Transitions*, Europhysics Letters, 101, 20007, 2013

[5] C. IOANA, A. DIGULESCU, A. SERBANESCU, I. CANDEL, F.-M. BIRLEANU – *Recent Advances in Non-stationary Signal Processing Based on the Concept of Recurrence Plot Analysis*, Springer Proc. in Mathematics & Statistics, M. Marwan et al. (Eds.): “Translational Recurrences”, pp. 75-93, Cham, Switzerland, 2014

[6] M. SMALL– *Applied Nonlinear Time Series Analysis: Applications in Physics, Physiology and Finance*, World Scientific Publishing, Toh Tuch Link, Singapore, 2005

[7] ] F.M. BIRLEANU, I. CANDEL, C. IOANA, C. GERVAISE, A. SERBANESCU, G. SERBAN – *A Vector Approach to Transient Signal Processing*,Proc. of the 11th International Conference on Information Science, ISSPA 2012, pp. 1174-1179, Montreal, Canada, Jul. 3-5, 2012

[8] ] I. CANDEL, F. BUNEA, G. DUNCA, D.M. BUCUR, C. IOANA, B. REEB, G.D. CIOCAN – *Detection of Cavitation Vortex in Hydraulic Turbines using Acoustic Techniques*, The 27th IAHR Symposium on Hydraulic Machinery and Systems, IAHR 2014, IOP Conference Series: Earth and Environmental Science, Vol. 22, pp. 1-8, Montreal, Canada, Sep. 22-26, 2014