Analysis of the pressure fields in a swirling annular jet flow

Download

index.pdf

Date

2017-12-01

Author

Perçin, Mustafa
van Oudheusden, B. W.

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

119
views

80
downloads

In this paper, we investigate the flow structures and pressure fields of a free annular swirling jet flow undergoing vortex breakdown. The flow field is analyzed by means of time-resolved tomographic particle image velocimetry measurements, which enable the reconstruction of the three-dimensional time-resolved pressure fields using the governing flow equations. Both time-averaged and instantaneous flow structures are discussed, including a characterization of the first-and second-order statistical moments. A Reynolds decomposition of the flow field shows that the time-averaged flow is axisymmetric with regions of high anisotropic Reynolds stresses. Two recirculation zones exist that are surrounded by regions of very intense mixing. Notwithstanding the axisymmetric nature of the time-averaged flow, a non-axisymmetric structure of the instantaneous flow is revealed, comprising a central vortex core which breaks up into a precessing vortex core. The winding sense of this helical structure is opposite to the swirl direction and it is wrapped around the vortex breakdown bubble. It precesses around the central axis of the flow at a frequency corresponding to a Strouhal number of 0.27. The precessing vortex core is associated with a low-pressure region along the central axis of the jet and the maximum pressure fluctuations occur upstream of the vortex breakdown location, where the azimuthal velocity component also reaches peak values as a result of the inward motion of the fluid and the conservation of angular momentum. The POD analysis of the pressure fields suggests that the precessing helical vortex formation is the dominant coherent structure in the instantaneous flow.

Subject Keywords

Swirling annular jet, Tomographic particle image velocimetry, Pressure reconstruction, Vortex breakdown

URI

https://hdl.handle.net/11511/37885

Journal

EXPERIMENTS IN FLUIDS

DOI

https://doi.org/10.1007/s00348-017-2446-3

Collections

Department of Aerospace Engineering, Article

Suggestions

OpenMETU
Core

Visualization of the structure of vortex breakdown in free swirling jet flow Vanierschot, Maarten; Perçin, Mustafa; Van Oudheusden, Bas W. (2016-07-04) In this paper we investigate the three dimensional flow structures in a free annular swirling jet flow undergoing vortex breakdown. The flow field is analyzed by means of time-resolved Tomographic Particle Image Velocimetry measurements. Both time-averaged and instantaneous flow structures are discussed, including a detailed analysis of the first and second order statistical moments. A Reynolds decomposition of the flow field shows that the time averaged flow is axisymmetric with regions of high anisotropic...
Experimental investigation of 3D flow field around a Flapping wing making figure-of-eight motion in hover Using PIV technique Ersöz, İrem; Alemdaroğlu, Hüseyin Nafiz; Department of Aerospace Engineering (2014) This thesis presents the results of experimental investigation of vortex formation around a three dimensional flapping wing making figure-of-eight motion in hovering flight at low Reynolds numbers. These results are compared with those obtained from previous computational and experimental studies of the same flapping motions. Analysis of vortex formations around the three dimensional flapping wing and the investigations of the effect of different parameters such as the amplitude of motion in y direction and...
Experimental Investigation of the Effects of Winglets on the Tip Vortex Behavior of a Model Horizontal Axis Wind Turbine Using Particle Image Velocimetry Ostovan, Yasar; Akpolat, M. Tugrul; Uzol, Oğuz (2019-02-01) This study presents an experimental investigation on the effects of winglets on the near wake flow around the tip region and on the tip vortex characteristics downstream of a 0.94 m diameter three-bladed horizontal axis wind turbine (HAWT) rotor. Phase-locked 2D particle image velocimetry (PIV) measurements are performed with and without winglets covering 120 deg of azimuthal progression of the rotor. The impact of using winglets on the flow field near the wake boundary as well as on the tip vortex characte...
Experimental analysis of flow structure on moderate sweep delta wing Öztürk, İlhan; Yavuz, Mehmet Metin; Department of Mechanical Engineering (2014) Experimental investigation of flow over a 45° moderate swept delta wing is performed using laser illuminated smoke visualization, surface pressure measurements, and Laser Doppler Anemometry (LDA) techniques in low-speed wind tunnel. The formation of leading-edge vortices and their breakdown, and three-dimensional separation from the surface of the wing are studied at broad range of attack angles and Reynolds numbers. Smoke visualizations are performed at three different cross flow planes along with vortex a...
Single- and double-helix vortex breakdown as two dominant global modes in turbulent swirling jet flow Vanierschot, Maarten; Mueller, Jens S.; Sieber, Moritz; Perçin, Mustafa; van Oudheusden, Bas W.; Oberleithner, Kilian (Cambridge University Press (CUP), 2020-01-25) In this paper, we study the shape and dynamics of helical coherent structures found in the flow field of an annular swirling jet undergoing vortex breakdown. The flow field is studied by means of time-resolved tomographic particle image velocimetry measurements. The obtained flow fields are analysed using both classic and spectral proper orthogonal decomposition. Despite the simple geometrical set-up of the annular jet, the flow field is very complex. Two distinct large-scale helical flow structures are ide...

Citation Formats

M. Perçin and B. W. van Oudheusden, “Analysis of the pressure fields in a swirling annular jet flow,” EXPERIMENTS IN FLUIDS, pp. 0–0, 2017, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/37885.