Phase-locked 3D3C-MRV measurements in a bi-stable fluidic oscillator

In this work, the phase-resolved internal flow of a bi-stable fluidic oscillator was measured using phase-locked three-dimensional three-components magnetic resonance velocimetry (3D3C-MRV), also termed as 4D-MRV. A bi-stable fluidic oscillator converts a continuous inlet-mass flow into a jet alternating between two outlet channels and, as a consequence provides an unsteady, periodic flow. This actuator can therefore be used as flow-control actuator. Since data acquisition in a 3D volume takes up to several minutes, only a small portion of the data is acquired in each flow cycle for every time point of the flow cycle. The acquisition of the entire data set is segmented over many cycles of the periodic flow. This procedure allows to measure phase-averaged 3D3C velocity fields with a certain temporal resolution. However, the procedure requires triggering to the periodic nature of the flow. Triggering the MR scanner precisely on each flow cycle is one of the key issues discussed in this manuscript. The 4D-MRV data are compared to data measured using phase-locked laser Doppler anemometry and good agreement between the results is found. The validated 4D-MRV data is analyzed and the fluid-mechanic features and processes inside the fluidic oscillator are investigated and described, providing a detailed description of the internal jet-switching mechanism.

[1]  B. Nishri,et al.  Effects of Periodic Excitation on Turbulent Flow Separation from a Flap , 1998 .

[2]  Israel J Wygnanski,et al.  Active management of naturally separated flow over a solid surface. Part 1. The forced reattachment process , 2004, Journal of Fluid Mechanics.

[3]  C. Tropea,et al.  Experimental investigation of helical structures in swirling flows , 2012 .

[4]  G. Papadopoulos,et al.  Jet thrust vectoring using a miniature fluidic oscillator , 2005, The Aeronautical Journal (1968).

[5]  Michael Markl,et al.  Time‐resolved three‐dimensional phase‐contrast MRI , 2003, Journal of magnetic resonance imaging : JMRI.

[6]  J. Hennig,et al.  3D MR flow analysis in realistic rapid‐prototyping model systems of the thoracic aorta: Comparison with in vivo data and computational fluid dynamics in identical vessel geometries , 2008, Magnetic resonance in medicine.

[7]  I. Wygnanski,et al.  Oscillatory Blowing: A Tool to Delay Boundary-Layer Separation , 1993 .

[8]  Louis N. Cattafesta,et al.  Actuators for Active Flow Control , 2011 .

[9]  Wolfgang Nitsche,et al.  Piezo-electric foils as a means of sensing unsteady surface forces , 1989 .

[10]  Christopher J. Elkins,et al.  Magnetic resonance velocimetry: applications of magnetic resonance imaging in the measurement of fluid motion , 2007 .

[11]  Hermann Viets,et al.  Flip-Flop Jet Nozzle , 1975 .

[12]  Avi Seifert,et al.  Suction and Oscillatory Blowing Actuator Modeling and Validation , 2008 .

[13]  Ganesh Raman,et al.  Evaluation of Flip-Flop Jet Nozzles for Use as Practical Excitation Devices , 1994 .

[14]  Yu-Chung N. Cheng,et al.  Magnetic Resonance Imaging: Physical Principles and Sequence Design , 1999 .

[15]  Václav Tesař,et al.  No-moving-part hybrid-synthetic jet actuator , 2006 .

[16]  Christian Oliver Paschereit,et al.  Active Combustion Control Using a Fluidic Oscillator for Asymmetric Fuel Flow Modulation , 2008 .

[17]  Norbert J. Pelc,et al.  4D Magnetic resonance velocimetry for mean velocity measurements in complex turbulent flows , 2003 .

[18]  James W. Gregory,et al.  Visualization of jet mixing in a fluidic oscillator , 2005, J. Vis..

[19]  Jing-Tang Yang,et al.  A novel fluidic oscillator incorporating step-shaped attachment walls , 2007 .

[20]  V. Tesař,et al.  Bistable diverter valve in microfluidics , 2011 .

[21]  Dennis E. Culley,et al.  Numerical Studies of a Fluidic Diverter for Flow Control , 2009 .

[22]  Philipp Tewes,et al.  Discrete Sweeping Jets as Tools for Improving the Performance of the V-22 , 2009 .

[23]  Feng Huang,et al.  k‐t GRAPPA: A k‐space implementation for dynamic MRI with high reduction factor , 2005, Magnetic resonance in medicine.

[24]  Avi Seifert,et al.  Large Trucks Drag Reduction using Active Flow Control , 2008 .