scholarly journals Numerical Modeling of Active Flow Control in a Boundary Layer Ingesting Offset Inlet

2004 ◽  
Author(s):  
Brian Allan ◽  
Lewis Owens ◽  
Bobby Berrier
Keyword(s):  
Boundary Layer ◽  
Numerical Modeling ◽  
Flow Control ◽  
Active Flow Control ◽  
Active Flow

Interaction Phenomena of High Frequency Pulsed Blowing in LP Turbine-Like Boundary Layers at High Speed Test Conditions

2018 ◽  
Author(s):  
Valentin Bettrich ◽  
Martin Bitter ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Boundary Layer Flow ◽  
High Frequency ◽  
Active Flow Control ◽  
Suction Side ◽  
Operating Point ◽  
Layer Flow ◽  
Lp Turbine ◽  
Active Flow

The use of fluidic oscillators for active flow control applications is a proven and efficient concept. For the well-known highly loaded LP turbine profile T161, the total pressure losses could already reduced by 40% at low Reynolds numbers, were usually flow separation occurs. For further improvements of the active flow control concept, it is essential to understand the driving flow phenomena responsible for the loss reduction mechanism, which are discussed in this paper. The results presented are based on experimental investigations on a flat plate with pressure gradient, imposed with an aerodynamically highly loaded low pressure turbine suction side flow and equipped with active flow control. The analogy to the suction side of the T161 is shown and validated against former cascade measurements. Based on the T161 equivalent operating point of Re = 70,000 and a theoretical out flow Mach number of Ma2,th = 0.6, the focus is set on the interaction of the boundary layer flow with high frequency actuation. The chosen actuator, a high frequency coupled fluidic oscillator, is designed to independently adjust mass flow and frequency. The flat plate is equipped with an array of high frequency actuators to control the flow separation. For this study one oscillator operating point at 6.7kHz is presented and the influence on transition and loss reduction compared to the non-actuated case is discussed. This oscillator operating point was found to be most efficient and the steady and unsteady mixing behavior of the high frequency actuator impact and the low pressure turbine like suction side boundary layer flow is investigated in much detail. Depending on the measurement technique, the isentropic Mach number distribution, frequency spectra, standard deviation, skewness and kurtosis are evaluated. The most important results are on the one hand, that the chosen concept is more efficient compared to former studies in means of mass flow investment, which is mainly based on the chosen oscillator outlet position and frequency. On the other hand, in a transonic flow the mixing and interaction of the high frequency pulses and the boundary layer flow require about 10% of the surface length to even establish and about to 30% to be completed. These results of the mixing behavior between actuator and boundary layer for compressible flow conditions help to attain a fundamental understanding for future designs of active flow control concepts.

Active Flow Control of a Boundary Layer-Ingesting Serpentine Inlet Diffuser

2013 ◽  
Vol 50 (1) ◽  
pp. 262-271 ◽  
Author(s):  
Neal A. Harrison ◽  
Jason Anderson ◽  
Jon L. Fleming ◽  
Wing F. Ng
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Active Flow Control ◽  
Active Flow

Detailed Analysis of Boundary Layer Control by Fluidic Oscillators on a Highly Loaded Profile

2018 ◽  
Author(s):  
Julia Kurz ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Flow Separation ◽  
High Speed ◽  
Active Flow Control ◽  
Suction Side ◽  
Transition Process ◽  
Frequency Spectra ◽  
Active Flow ◽  
Highly Loaded

One application method of active flow control is the exploitation of the interaction between transition and flow separation on a profile. As turbulent flows are able to withstand higher adverse pressure gradients the enforcement of the transition process can be utilized to prevent or to reduce flow separation. This paper focuses on gaining a better understanding of high frequency active flow control (AFC) by fluidic oscillators and its influence on the transition process for a separated boundary layer. Flow control is applied on a highly loaded turbine exit case (TEC) profile which was in particular designed for this application. The profile is investigated in the high-speed cascade wind tunnel at the Bundeswehr University Munich. Significant loss reduction by AFC could be observed by total pressure loss determination in the low Reynolds number regime. In order to gain a better understanding of development of the suction side boundary layer, several boundary layer profiles are determined by hot-wire measurements at six axial positions on the suction side of the profile. Differences between the boundary layer development and the extent of the separation can be detected. Furthermore, a stability analysis of the boundary layer upstream of separation is conducted and compared to the measured frequency spectra.

Use of Micro Synthetic Jet Actuators for Boundary Layer Flow Control

2009 ◽  
Vol 74 ◽  
pp. 157-160
Author(s):  
Jing Chuen Lin ◽  
An Shik Yang ◽  
Li Yu Tseng
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Turbulent Flows ◽  
Boundary Layer Flow ◽  
Moving Boundary ◽  
Active Flow Control ◽  
Flow Characteristics ◽  
Synthetic Jet ◽  
Layer Flow ◽  
Active Flow

The main purpose of active flow control research is to develop a cost-effective technology that has the potential for inventive advances in aerodynamic performance and maneuvering compared to conventional approaches. It can be essential to thoroughly understand the flow characteristics of the formation and interaction of a synthetic jet with external crossflow before formulating a practicable active flow control strategy. In this study, the theoretical model used the transient three-dimensional conservation equations of mass and momentum for compressible, isothermal, turbulent flows. The motion of a movable membrane plate was also treated as the moving boundary by prescribing the displacement on the plate surface. The predictions by the computational fluid dynamics (CFD) code ACE+® were compared with measured transient phase-averaged velocities of Rumsey et al. for software validation. The CFD software ACE+® was utilized for numerical calculations to probe the time evolution of the development process of the synthetic jet and its interaction within a turbulent boundary layer flow for a complete actuation cycle.

Active Flow Control With an Oscillating Backward Facing Step in a Shallow Open Channel

2012 ◽  
Author(s):  
Sertac Cadirci ◽  
Hasan Gunes
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Flow Separation ◽  
Open Channel ◽  
Recirculation Zone ◽  
Active Flow Control ◽  
Computational Domain ◽  
Backward Facing Step ◽  
Induced Flow ◽  
Active Flow

An oscillatory, zero-net-mass flux actuator system, Jet and Vortex Actuator (JaVA), is implemented on the step wall of a backward facing step. JaVA can energize the boundary layer by creating jets or vortices thus it may delay flow separation when used properly. The main part of JaVA is a rectangular cavity with a moving actuator plate. The actuator plate is mounted asymmetrically inside the cavity of the JaVA box, such that there are one narrow and one wide gap between the plate and the box. The main governing parameters are the actuator plate’s width (b), the amplitude (a) and the operating frequency (f). The main target of the control with active jets on the step wall is to influence directly the main recirculation zone, thus as the actuator plate or the step’s vertical wall moves periodically in horizontal direction, a jet emerges into the recirculation zone. Non-dimensional numbers such as the scaled amplitude (Sa = 2πa/b) and the jet Reynolds number (ReJ = 4abf/ν) as well as the cross flow parameter characterize the JaVA-induced flow types and the effects on the recirculation zone. One period consists of one blowing and one suction phase into the recirculation zone. Boundary layer profiles extracted from time-averaged flow fields of the not actuated (f = 0) and actuated cases at various operating frequencies indicate the effect of active flow control. The interaction between JaVA-induced flow regimes and the boundary layer is investigated numerically in an open channel with a BFS. The computational domain consists of a moving zone along the channel and the motion of the actuator plate is generated by a moving grid imposing appropriate boundary conditions with User-Defined-Functions and the calculations are carried out by a commercial finite-volume-based unsteady, laminar, incompressible Navier-Stokes solver. Numerical simulations and comparisons reveal the JaVA-boundary layer interaction for various governing parameters. Reynolds numbers based on the step height for the shallow open channel flow are Reh = 225 and 450. The proposed control method based on suction and blowing with an oscillating vertical step seems to be effective in shortening the recirculation zone length and delaying the flow separation downstream of the backward facing step.

scholarly journals Active Flow Control in a Radial Vaned Diffuser for Surge Margin Improvement: A Multislot Suction Strategy

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Aurélien Marsan ◽  
Isabelle Trébinjac ◽  
Stéphane Moreau ◽  
Sylvain Coste
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Active Flow Control ◽  
Control Technique ◽  
Navier Stokes ◽  
Compressor Stage ◽  
Vaned Diffuser ◽  
Boundary Layer Suction ◽  
Surge Margin ◽  
Active Flow

This work is the final step of a research project that aims at evaluating the possibility of delaying the surge of a centrifugal compressor stage using a boundary-layer suction technique. It is based on Reynolds-Averaged Navier-Stokes numerical simulations. Boundary-layer suction is applied within the radial vaned diffuser. Previous work has shown the necessity to take into account the unsteady behavior of the flow when designing the active flow control technique. In this paper, a multislot strategy is designed according to the characteristics of the unsteady pressure field. Its implementation results in a significant increase of the stable operating range predicted by the unsteady RANS numerical model. A hub-corner separation still exists further downstream in the diffuser passage but does not compromise the stability of the compressor stage.

Multidisciplinary design optimisation of a fully electric regional aircraft wing with active flow control technology

2021 ◽  
pp. 1-25
Author(s):  
V. Mosca ◽  
S. Karpuk ◽  
A. Sudhi ◽  
C. Badrya ◽  
A. Elham
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Electric Propulsion ◽  
Active Flow Control ◽  
Multidisciplinary Design ◽  
Aircraft Wing ◽  
Design Optimisation ◽  
Boundary Layer Suction ◽  
Active Flow ◽  
Multidisciplinary Design Optimisation

Abstract The German research Cluster of Excellence SE2A (Sustainable and Energy Efficient Aviation) is investigating different technologies to be implemented in the following decades, to achieve more efficient air transportation. This paper studies the Hybrid Laminar Flow Control (HLFC) using boundary layer suction for drag reduction, combined with other technologies for load and structural weight reduction and a novel full-electric propulsion system. A multidisciplinary design optimisation framework is presented, enabling physics-based analysis and optimisation of a fully electric aircraft wing equipped with HLFC technologies and load alleviation, and new structures and materials. The main focus is on simulation and optimisation of the boundary layer suction and its influence on wing design and optimisation. A quasi three-dimensional aerodynamic analysis is used for drag estimation of the wing. The tool executes the aerofoil analysis using XFOILSUC, which provides accurate drag estimation through boundary layer suction. The optimisation is based on a genetic algorithm for maximum take-off weight (MTOW) minimisation. The optimisation results show that the active flow control applied on the optimised geometry results in more than 45% reduction in aircraft drag coefficient, compared to the same geometry without HLFC technology. The power absorbed for the HLFC suction system implies a battery mass variation lower than 2%, considering the designed range as top-level requirement (TLR).

Active Flow Control in a Single-Stage Axial Compressor Using Tip Injection and Endwall Boundary Layer Removal

2008 ◽  
Author(s):  
B. Dobrzynski ◽  
H. Saathoff ◽  
G. Kosyna ◽  
C. Clemen ◽  
V. Gu¨mmer
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Active Flow Control ◽  
Stall Margin ◽  
Operating Range ◽  
Oil Flow ◽  
Tip Injection ◽  
Active Flow ◽  
The Impact ◽  
Stage Efficiency

Different active flow control techniques have been investigated in a 1.5-stage axial-flow compressor. Looking at a low-speed single-stage environment, many researchers have shown that highly loaded compressors are tip critical, showing stall inception caused by short length scale disturbances (spikes). It has been shown by several authors that these disturbances are related to the spillage of endwall flow ahead of the blading (spill forward). For the present work, different tip injection configurations were investigated in order to stabilize the near casing flow, increasing the operating range of the compressor. Stall margin improvement and the impact on stage efficiency are compared and discussed. Oil flow pictures of the casing wall above the rotor and of the stator blades as well as traverse data from pneumatic 5-hole probes show the impact of flow control on rotor and stator performance. Another method of energizing the casing wall boundary layer is the removal of low energy fluid by a circumferential slot above the rotor, which was also studied experimentally. Again, the impact on compressor operating range and efficiency, as well as flow field information collected by oil flow visualization and traverse data are discussed. Comparing the different flow control techniques, it is shown that increasing stall margin is not directly linked to stage efficiency. As described in various publications, discrete tip injection is a very powerful technique as far as range extension is concerned, but it also has substantial drawbacks such as the circumferential inhomogeneity of the rotor exit flow. These inhomogeneities may result in poor stator performance, overall resulting in a drop of stage efficiency. This problem does not occur if circumferential boundary layer removal above the rotor is used. This method however shows much less potential for increasing the operating range.

Design of a Low Solidity Flow-Controlled Stator With Coanda Surface in a High Speed Compressor

2008 ◽  
Author(s):  
Y. Guendogdu ◽  
A. Vorreiter ◽  
J. R. Seume
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
High Speed ◽  
Design Method ◽  
Active Flow Control ◽  
Suction Side ◽  
Boundary Layer Separation ◽  
Synthetic Jets ◽  
Layer Separation ◽  
Active Flow

Aerofoil active flow control has been attempted to increase the permissible loading of boundary layers in gas turbine components. Steady suction and blowing, pulsing and synthetic jets are all means to remove low energy flow, replace momentum deficits, or promote mixing to inhibit boundary layer separation. A curved surface near the trailing edge (“Coanda surface”) is another technique used to control aerofoil boundary layer separation. This paper presents the design of a stator with active flow control for a high speed compressor using a Coanda surface. The Coanda surface is located behind an injection slot on the aerofoil suction side of the first stage of a four-stage high speed research compressor. The design method and the present results are based on steady numerical calculations. The design intent is to reduce the number of vanes. This active flow control is used to maintain the flow exit angle of the reference stator despite the resulting increase in stator loading. It is shown that the solidity of the flow-controlled stator can be decreased by 25% with a blowing rate of 0.5% of the main mass flow.

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