Numerical simulation of flow control techniques for separation control

2002 ◽  
Author(s):  
M. Patel ◽  
A. Cain
Keyword(s):  
Numerical Simulation ◽  
Flow Control ◽  
Separation Control ◽  
Control Techniques

scholarly journals Interpretation of Four Unique Phenomena and the Mechanism in Unsteady Flow Separation Controls

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 587 ◽  
Author(s):  
Weiyu Lu ◽  
Guoping Huang ◽  
Jinchun Wang ◽  
Yuxuan Yang
Keyword(s):  
Numerical Simulation ◽  
Unsteady Flow ◽  
Flow Control ◽  
Flow Separation ◽  
Flow Instability ◽  
Control Flow ◽  
Separation Control ◽  
Pulsed Jet ◽  
Unsteady Separation ◽  
Flow Theories

Unsteady flow separation controls are effective in suppressing flow separations. However, the unique phenomena in unsteady separation control, including frequency-dependent, threshold, location-dependent, and lock-on effects, are not fully understood. Furthermore, the mechanism of the effectiveness that lies in unsteady flow controls remains unclear. Thus, this study aims to interpret further the unique phenomena and mechanism in unsteady flow separation controls. First, numerical simulation and some experimental results of a separated curved diffuser using pulsed jet flow control are discussed to show the four unique phenomena. Second, the bases of unsteady flow control, flow instability, and free shear flow theories are introduced to elucidate the unique phenomena and mechanism in unsteady flow separation controls. Subsequently, with the support of these theories, the unique phenomena of unsteady flow control are interpreted, and the mechanisms hidden in the phenomena are revealed.

Electroosmotic Flow Control in Complex Microgeometries

2000 ◽  
Author(s):  
Prashanta Dutta ◽  
Ali Beskok
Keyword(s):  
Flow Control ◽  
Electroosmotic Flow ◽  
Spectral Element Method ◽  
Spectral Element ◽  
Separation Control ◽  
Control Techniques ◽  
Pressure Distributions ◽  
Flow Adjustment ◽  
Analytical Relations ◽  
P Type

Abstract A high-order (h/p type) spectral element method is developed, and verified for numerical simulation of combined electroosmotic and pressure driven flows in complex microgeometries. Analytical relations for wall shear stress, velocity and pressure distributions in straight channels are obtained. The electrokinetic pumping action is demonstrated. Electroosmotic flows in groove-channels, microchannel junctions and Y-split junctions are analyzed. Precise flow adjustment and separation control techniques using the electroosmotic forces are demonstrated. In the Stokes flow regime, the flow control is shown to have linear dependence on the magnitude of the external electric field. Hence, the electroosmotic forces can be used as linear actuators for various microfluidic applications.

Flow Control Around a SUV Simplified Vehicle

2018 ◽  
Author(s):  
Stéphie Edwige ◽  
Philippe Gilotte ◽  
Iraj Mortazavi ◽  
Yoann Eulalie ◽  
David Holst ◽  
...  
Keyword(s):  
Drag Reduction ◽  
Flow Control ◽  
Time Scale ◽  
Pressure Coefficient ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Decomposition Algorithms ◽  
Reference Case ◽  
Control Techniques ◽  
Run Time

The research on the external aerodynamics of ground vehicles can nowadays be related to sustainable development strategies, confirmed by the worldwide CO2 regulation target. Automotive manufacturers estimate that a drag reduction of 30% contributes to 10g/km of CO2 reduction. However, this drag reduction should be obtained without constraints on the design, the safety, comfort and habitability of the passengers. Thus, it is interesting to find flow control solutions, which will remove or remote recirculation zones due to separation edges with appropriate control techniques. In automotive sales, the SUV, 4x4 and compact cars represent a large part of the market share and the study of control approaches for this geometry is practically useful. In this work, appropriate control techniques are designed to decrease the drag forces around a reduced scale SUV car benchmark called POSUV. The control techniques are based on the DMD (Dynamic Mode Decomposition) algorithms generating an optimized drag reduction procedure. It involves independent transient inflow boundary conditions for flow control actuation in the vicinity of the separation zones and time resolved pressure sensor output signals on the rear end surface of the mockup. This study, that exploits dominant flow features behind the tailgate and the rear bumper, is performed using Large Eddy Simulations on a sufficient run time scale, in order to minimize a cost function dealing with the time and space average pressure coefficient. The resulting dynamic modal decomposition obtained by these LES simulations and by wind tunnel measurements has been compared for the reference case, in order to select the most appropriate run time scale. Analysis of the numerical results shows a significant pressure increase on the tailgate, for independent flow control frequencies. Similar decomposition performed in the wake with and without numerical flow control help understanding the flow modifications in the detachment zones.

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