Active Control of Transpiration Boundary Conditions for Drag Minimization with an Euler CFD Solver

2007 ◽  
Author(s):  
Raymond Kolonay ◽  
Ernest Thompson ◽  
Jose Camberos ◽  
Frank Eastep
Keyword(s):  
Boundary Conditions ◽  
Active Control ◽  
Drag Minimization

Hyperplastic Forming: Process Potential and Factors Affecting Formability

1999 ◽  
Vol 601 ◽  
Author(s):  
Glenn S. Daehn ◽  
Vincent J. Vohnout ◽  
Subrangshu Datta
Keyword(s):  
Boundary Conditions ◽  
Sample Size ◽  
Active Control ◽  
High Velocity ◽  
Size Dependence ◽  
Recent Model ◽  
The Body ◽  
Electromagnetic Forming ◽  
Forming Process ◽  
Factors Affecting

AbstractThis paper has two distinct goals. First, we argue in an extended introduction that high velocity forming, as can be implemented through electromagnetic forming, is a technology that should be developed. As a process used in conjunction with traditional stamping, it may offer dramatically improved formability, reduced wrinkling and active control of springback among other advantages. In the body of the paper we describe the important factors that lead to improved formability at high velocity. In particular, high sample velocity can inhibit neck growth. There is a sample size dependence where larger samples have better ductility than those of smaller dimensions. These aspects are at least partially described by the recent model of Freund and Shenoy. In addition to this, boundary conditions imposed by sample launch and die impact can have important effects on formability.

Influence of Boundary Conditions on the Active Control of Vibration and Sound Radiation for a Circular Cylindrical Shell

2011 ◽  
Vol 66-68 ◽  
pp. 1270-1277
Author(s):  
Lu Dai ◽  
Tie Jun Yang ◽  
Yao Sun ◽  
Ji Xin Liu
Keyword(s):  
Cylindrical Shell ◽  
Boundary Conditions ◽  
Active Control ◽  
Structural Engineering ◽  
Acoustic Radiation ◽  
Circular Cylindrical Shell ◽  
Acoustic Power ◽  
Fourier Series Method ◽  
Vibration And Sound Radiation ◽  
Elastically Restrained

Vibration and acoustic radiation of circular cylindrical shells are hot topics in the structural engineering field. However for a long period, this sort of problems is only limit to classical homogeneous boundary conditions. In this paper, the vibration of a circular cylindrical shell with elastic boundary supports is studied using modified Fourier series method, and the far-field pressure for a baffled shell is calculated by Helmholtz integral equation. Active control of vibration and acoustic radiation are carried out by minimizing structural kinetic energy and radiated acoustic power respectively. The influence of boundary conditions on the active control is investigated throughout several numerical examples. It is shown that the active control of vibration and acoustic for an elastically restrained shell can exhibit unexpected and complicated behaviors.

Active control of boundary conditions for dynamic thermal characterization of electronic components

2013 ◽  
Vol 44 (11) ◽  
pp. 1019-1024 ◽  
Author(s):  
Marcin Janicki ◽  
Tomasz Torzewicz ◽  
Zbigniew Kulesza ◽  
Andrzej Napieralski
Keyword(s):  
Boundary Conditions ◽  
Active Control ◽  
Thermal Characterization ◽  
Electronic Components

Using Numerical Models to Complement Experimental Setups by Means of Active Control of Mobility

2011 ◽  
Vol 70 ◽  
pp. 357-362 ◽  
Author(s):  
Timo Jungblut ◽  
Stefan Wolter ◽  
Michael Matthias ◽  
Holger Hanselka
Keyword(s):  
Boundary Conditions ◽  
Dynamic Behavior ◽  
Active Control ◽  
Numerical Models ◽  
Test Facility ◽  
Active Systems ◽  
Laboratory Environment

The behavior of a component observed after implementation might differ from the characteristic that was determined in laboratory before. These deviations are often caused by discrepancies in the boundary conditions between the field and laboratory environment. Active control of mobility allows replicating the boundary conditions as well as the dynamic behavior of adjoining subsystems within the test facility by means of active systems. Numerical models are used in order to simulate the behavior of the missing subsystems experimentally. Within this contribution two realizations from different fields of engineering are presented.

Active Control of the Acoustic Boundary Conditions of Combustion Test Rigs: Extension to Actuators With Non-Linear Response

2009 ◽  
Author(s):  
Mirko R. Bothien ◽  
Christian Oliver Paschereit
Keyword(s):  
Boundary Conditions ◽  
Active Control ◽  
Linear Response ◽  
Full Scale ◽  
Operating Conditions ◽  
Test Rig ◽  
Acoustic Boundary Conditions ◽  
Control Scheme ◽  
Resonance Frequencies ◽  
Non Linear

In the design process, new burners are generally tested in combustion test rigs. With these experiments, as well as with CFD, finite element calculations, and low-order network models, the burner’s performance in the full-scale engine is sought to be predicted. Especially, information about the thermoacoustic behaviour and the emissions is very important. As the thermoacoustics strongly depend on the acoustic boundary conditions of the system, it is obvious that test rig conditions should match or be close to those of the full-scale engine. This is, however, generally not the case. Hence, if the combustion process in the test rig is stable at certain operating conditions, it may show unfavourable dynamics at the same conditions in the engine. In previous works, the authors introduced an active control scheme which is able to mimic almost arbitrary acoustic boundary conditions. Thus, the test rig properties can be tuned to correspond to those of the full-scale engine. The acoustic boundary conditions were manipulated using woofers. In the present study, an actuator with higher control authority is investigated, which could be used to apply the control scheme in industrial test rigs. The actuator modulates an air mass flow to generate an acoustic excitation. However, in contrast to the woofers, it exhibits a strong non-linear response regarding amplitude and frequency. Thus, the control scheme is further developed to account for these non-linear transfer characteristics. This modified control scheme is then applied to change the acoustic boundary conditions of an atmospheric swirl-stabilized combustion test rig. Excellent results were obtained in terms of changing the reflection coefficient to different levels. By manipulating its phase, different resonance frequencies could be imposed without any hardware changes. The non-linear control approach is not restricted to the actuator used in this study and might therefore be of use for other actuators as well.

Impedance Tuning of a Premixed Combustor Using Active Control

2007 ◽  
Author(s):  
Mirko R. Bothien ◽  
Jonas P. Moeck ◽  
Christian Oliver Paschereit
Keyword(s):  
Boundary Conditions ◽  
Combustion Chamber ◽  
Active Control ◽  
Combustion Process ◽  
Reacting Flow ◽  
Acoustic Behavior ◽  
Acoustic Boundary Conditions ◽  
Early Design ◽  
Resonance Frequencies ◽  
Arbitrary Frequency

In early design phases new burner concepts are mostly tested in single or multi burner test rigs. These test rigs generally exhibit a different acoustic behavior than the full scale engine. The acoustic behavior, however, is crucial to predict whether thermoacoustic instabilities are likely to occur. Tuning the test rig’s acoustic boundary conditions to that of the engine could overcome this issue. Through this, an effective assessment of new burners is possible even in early design phases. In this work a method is proposed, which uses an active control scheme to manipulate the acoustic boundary conditions. It is applied to an atmospheric combustor test rig with a swirl-stabilized burner. In a first step it is shown that the acoustic boundary conditions can be controlled in the cold flow case. Almost arbitrary frequency dependent impedances can be prescribed ranging from fully reflecting (both pressure and velocity node) to anechoic. In particular, an additional virtual length can be added to the combustor outlet by manipulation of the reflection coefficient’s phase. This introduces resonance frequencies different from those of the uncontrolled case. In a second step the impedance tuning concept is applied to the reacting flow. It is demonstrated that the concept is feasible despite the harsh environmental conditions in a combustion chamber. The effect of different levels of reflection at the combustion chamber outlet on the combustion process is investigated. In addition to that, a study of the influence of the simulated combustor length on the system’s resonance frequencies is conducted.

Active control of the acoustic boundary conditions of combustion test rigs

2008 ◽  
Vol 318 (4-5) ◽  
pp. 678-701 ◽  
Author(s):  
Mirko R. Bothien ◽  
Jonas P. Moeck ◽  
Christian Oliver Paschereit
Keyword(s):  
Boundary Conditions ◽  
Active Control ◽  
Acoustic Boundary Conditions

Tuning of the Acoustic Boundary Conditions of Combustion Test Rigs With Active Control: Extension to Actuators With Nonlinear Response

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Mirko R. Bothien ◽  
Christian Oliver Paschereit
Keyword(s):  
Boundary Conditions ◽  
Active Control ◽  
Nonlinear Response ◽  
Combustion Process ◽  
Full Scale ◽  
Operating Conditions ◽  
Test Rig ◽  
Acoustic Boundary Conditions ◽  
Control Scheme ◽  
Resonance Frequencies

In the design process, new burners are generally tested in combustion test rigs. With these experiments, as well as with computational fluid dynamics, finite element calculations, and low-order network models, the burner’s performance in the full-scale engine is sought to be predicted. Especially, information about the thermoacoustic behavior and the emissions is very important. As the thermoacoustics strongly depend on the acoustic boundary conditions of the system, it is obvious that test rig conditions should match or be close to those of the full-scale engine. This is, however, generally not the case. Hence, if the combustion process in the test rig is stable at certain operating conditions, it may show unfavorable dynamics at the same conditions in the engine. In previous works, the authors introduced an active control scheme, which is able to mimic almost arbitrary acoustic boundary conditions. Thus, the test rig properties can be tuned to correspond to those of the full-scale engine. The acoustic boundary conditions were manipulated using woofers. In the present study, an actuator with higher control authority is investigated, which could be used to apply the control scheme in industrial test rigs. The actuator modulates an air mass flow to generate an acoustic excitation. However, in contrast to the woofers, it exhibits a strong nonlinear response regarding amplitude and frequency. Thus, the control scheme is further developed to account for these nonlinear transfer characteristics. This modified control scheme is then applied to change the acoustic boundary conditions of an atmospheric swirl-stabilized combustion test rig. Excellent results were obtained in terms of changing the reflection coefficient to different levels. By manipulating its phase, different resonance frequencies could be imposed without any hardware changes. The nonlinear control approach is not restricted to the actuator used in this study and might therefore be of use for other actuators as well.

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