Assessment of Energetic Flow Control Techniques Using an Energy-Based Methodology

2007 ◽  
Author(s):  
Charles Suchomel ◽  
David Van Wie ◽  
D. Tejtel
Keyword(s):  
Flow Control ◽  
Control Techniques

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.

A comparison of different unsteady flow control techniques in a highly loaded compressor cascade

2018 ◽  
Vol 233 (6) ◽  
pp. 2051-2065 ◽  
Author(s):  
Hongxin Zhang ◽  
Shaowen Chen ◽  
Yun Gong ◽  
Songtao Wang
Keyword(s):  
Unsteady Flow ◽  
Flow Control ◽  
Flow Separation ◽  
Synthetic Jet ◽  
Control Technique ◽  
Compressor Cascade ◽  
Optimum Result ◽  
Control Techniques ◽  
Constant Suction ◽  
Highly Loaded

A numerical research is applied to investigate the effect of controlling the flow separation in a certain highly loaded compressor cascade using different unsteady flow control techniques. Firstly, unsteady pulsed suction as a new novel unsteady flow control technique was proposed and compared to steady constant suction in the control of flow separation. A more exciting effect of controlling the flow separation and enhancing the aerodynamic performance for unsteady pulsed suction was obtained compared to steady constant suction with the same time-averaged suction flow rate. Simultaneously, with the view to further exploring the potential of unsteady flow control technique, unsteady pulsed suction, unsteady pulsed blowing, and unsteady synthetic jet (three unsteady flow control techniques) are analyzed comparatively in detail by the related unsteady aerodynamic parameters such as excitation location, frequency, and amplitude. The results show that unsteady pulsed suction shows greater advantage than unsteady pulsed blowing and unsteady synthetic jet in controlling the flow separation. Unsteady pulsed suction and unsteady synthetic jet have a wider range of excitation location obtaining positive effects than unsteady pulsed blowing. The ranges of excitation frequency and excitation amplitude for unsteady pulsed suction gaining favorable effects are both much wider than that of unsteady pulsed blowing and unsteady synthetic jet. The optimum frequencies of unsteady pulsed suction, unsteady pulsed blowing, and unsteady synthetic jet are found to be different, but these optimum frequencies are all an integer multiple of the natural frequency of vortex shedding. The total pressure loss coefficient is reduced by 16.98%, 16.55%, and 17.38%, respectively, when excitation location, frequency, and amplitude are all their own optimal values for unsteady pulsed suction, unsteady pulsed blowing, and unsteady synthetic jet. The optimum result of unsteady synthetic jet only slightly outperforms that of unsteady pulsed suction and unsteady pulsed blowing. But unfortunately, there is no advantage from the standpoint of overall efficiency for the optimum result of unsteady synthetic jet because the slight improvement has to require a greater power consumption than the unsteady pulsed suction and unsteady pulsed blowing methods.

CFD-Based Simulation of Inlet Unstart Phenomena: Toward Supersonic Inlet Flow Control Techniques

2003 ◽  
Author(s):  
Daniel N. Miller ◽  
Brian R. Smith
Keyword(s):  
Steady State ◽  
Flow Control ◽  
High Speed ◽  
Steady State Solution ◽  
Accurate Solution ◽  
Back Pressure ◽  
Inlet Flow ◽  
Control Techniques ◽  
Contour Plots ◽  
Inlet Unstart

A time-accurate, full Navier-Stokes, Computational Fluid Dynamics (CFD) analysis of a back-pressure-induced, high-speed inlet unstart event was conducted. The objective was to identify visible and quantitative flowfield characteristics prior to and during an unstart event. The CFD-based investigation was conducted on a 2-D wind-tunnel model geometry of a forebody and inlet at a freestream Mach number of 5. A sequence of steady-state solutions were run to map the inlet flowfield response to subsequent increases in back-pressure from a design value up to the point of imminent unstart. A time-accurate solution commenced, using the final steady-state solution as the initial condition. The CFD-derived inlet flowfield contour plots compared well with test-derived color schlieren images, while predictions for steady-state and transient wall pressure compared reasonably with test data. A CFD-based study of inlet flow control techniques will follow.

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