Passive Control of Transonic Cavity Flow

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
David G. MacManus ◽  
Diane S. Doran
Keyword(s):  
High Speed ◽  
Passive Control ◽  
Noise Suppression ◽  
Flow Behavior ◽  
Leading Edge ◽  
Cavity Flow ◽  
Step Length ◽  
Geometric Feature ◽  
Sufficient Intensity ◽  
Grazing Flow

Open cavities at transonic speeds can result in acoustic resonant flow behavior with fluctuating pressure levels of sufficient intensity to cause significant damage to internal stores and surrounding structures. Extensive research in this field has produced numerous cavity flow control techniques, the more effective of which may require costly feedback control systems or entail other drawbacks such as drag penalties or rapid performance degradation at off-design condition. The current study focuses on the use of simple geometric modifications of a rectangular planform cavity with the aim of attenuating the aeroacoustic signature. Experiments were performed in an intermittent suck-down transonic wind tunnel by using a typical open flow rectangular planform cavity, which was modularly designed such that the leading and trailing edge geometries could be modified by using a family of inserts. The current work focused on a variety of recessed leading edge step arrangements. Configurations were tested at transonic Mach numbers spanning the range Mach 0.7–0.9, and unsteady pressure measurements were recorded at various stations within the cavity in order to obtain acoustic spectra. The most effective configuration at Mach 0.9 was the leading edge step employing a step height to step length ratio of 0.4. This configuration achieved a tonal attenuation of up to 18.6dB and an overall sound pressure level (OASPL) reduction of approximately 7.5dB. This is a significant level of noise suppression in comparison with other passive control methods. In addition, it offers the additional benefits of being a simple geometric feature, which does not rely on placing flow effectors into the high-speed grazing flow.

ANALYSIS OF THE EFFECTS OF MASS-INJECTION AT THE LEADING EDGE ON CAVITY FLOW CHARACTERISTICS

2009 ◽  
Vol 23 (03) ◽  
pp. 413-416 ◽  
Author(s):  
JI FEI WU ◽  
ZHAO LIN FAN ◽  
XIN FU LUO
Keyword(s):  
High Speed ◽  
Static Pressure ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Cavity Flow ◽  
Fluctuating Pressure ◽  
Pressure Distributions ◽  
Mass Injection ◽  
Varying Mass ◽  
Hole Number

An experimental investigation was conducted in a high speed wind tunnel to explore the effects of mass-injection on cavity flow characteristics. Detailed static-pressure and fluctuating pressure measurements were obtained at the cavity floor to enable the effects of the mass-injection at the leading edge to be determined. Results indicate that varying mass-injection hole number and the flux rate of mass-injection has no significant effect on cavity flow characteristics. However, mass-injection can reduce the cavity static pressure gradient when the cavity flow type is transitional-cavity flow. The study also indicates that Mach number can influence the effect of mass-injection on cavity fluctuating pressure distributions, and at supersonic speeds, mass-injection can suppress the cavity tones effectively.

Aeroacoustic Characteristics of Cavity and Effect Study of Mesh on Noise Suppression

2013 ◽  
Vol 421 ◽  
pp. 104-109
Author(s):  
Jing Sun ◽  
Guang Jun Yang ◽  
Jian Jun Liu
Keyword(s):  
Noise Reduction ◽  
Noise Suppression ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Cavity Flow ◽  
Noise Spectrum ◽  
Effect Study ◽  
Suppression Effect ◽  
Reduction Effect ◽  
Suppression Effects

To explore the noise suppression effect of mesh on cavity, the wind tunnel experiment is carried out based on the analysis of clean cavity flow characteristics. The meshes are arranged both in the cavity and at the leading edge of the cavity. Through the analysis of pressure distribution on the cavity bottom and the noise spectrum monitored at front and rear walls respectively, noise suppression effects of mesh programs relative to the clean cavity and changes in the flow field are studied, the results show that the mesh inside the cavity has a better noise reduction effect. The work in this paper provides an effective way for cavity noise reduction.

Effect of leading-edge plate controlling on subsonic cavity

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040090
Author(s):  
Fang-Qi Zhou ◽  
Dang-Guo Yang ◽  
Xian-Sheng Wang ◽  
Jun-Qiang Wu ◽  
Bo Lu
Keyword(s):  
High Speed ◽  
Noise Suppression ◽  
Static Pressure ◽  
Leading Edge ◽  
Wall Area ◽  
Flow Noise ◽  
Cavity Structure ◽  
Oil Flow ◽  
Field Information ◽  
The Impact

Cavity noise caused by the high-speed airflow has been paid much attention in the field of aerospace, and the study of cavity noise suppression has an important significance on improving the safety of aircraft. Effects of the leading-edge plate on the flow and the noise of the cavity model (the ratio of length to depth is 6) at a Mach number (Ma) of 0.6 are investigated with high-speed wind tunnel experiment. The acoustic and the flow field information in the cavity are obtained with the dynamic/static pressure measurement and oil flow experiment. The result shows that the leading-edge plate can greatly lift the shear layer, raise the impact position on the back-wall area, and reduce the flux rate and intensity in the cavity. With the controlling of leading-edge plate, the static pressure and backflow area are effectively suppressed and the SPL and peak noise also fall down significantly. The leading-edge plate provides a new method for cavity noise suppression in subsonic flow condition, which can be effectively applied to flow/noise controlling of cavity structure on aircraft.

scholarly journals Effects of Active and Passive Control Techniques on Mach 1.5 Cavity Flow Dynamics

2017 ◽  
Vol 2017 ◽  
pp. 1-24
Author(s):  
Selin Aradag ◽  
Kubra Asena Gelisli ◽  
Elcin Ceren Yaldir
Keyword(s):  
Passive Control ◽  
Control Method ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Cavity Flow ◽  
Flow Dynamics ◽  
Cover Plate ◽  
Control Methods ◽  
Trailing Edge ◽  
Control Techniques

Supersonic flow over cavities has been of interest since 1960s because cavities represent the bomb bays of aircraft. The flow is transient, turbulent, and complicated. Pressure fluctuations inside the cavity can impede successful weapon release. The objective of this study is to use active and passive control methods on supersonic cavity flow numerically to decrease or eliminate pressure oscillations. Jet blowing at several locations on the front and aft walls of the cavity configuration is used as an active control method. Several techniques are used for passive control including using a cover plate to separate the flow dynamics inside and outside of the cavity, trailing edge wall modifications, such as inclination of the trailing edge, and providing curvature to the trailing edge wall. The results of active and passive control techniques are compared with the baseline case in terms of pressure fluctuations, sound pressure levels at the leading edge, trailing edge walls, and cavity floor and in terms of formation of the flow structures and the results are presented. It is observed from the results that modification of the trailing edge wall is the most effective of the control methods tested leading to up to 40 dB reductions in cavity tones.

scholarly journals Leading edge stability in motile cells is an emergent property of branched actin network growth

2020 ◽  
Author(s):  
Rikki M. Garner ◽  
Julie A. Theriot
Keyword(s):  
High Speed ◽  
Noise Suppression ◽  
Animal Cell ◽  
Leading Edge ◽  
Lateral Spreading ◽  
Actin Network ◽  
Biological Noise ◽  
Network Growth ◽  
Motile Cells ◽  
Branch Formation

AbstractAnimal cell migration is predominantly driven by the coordinated, yet stochastic, polymerization of thousands of nanometer-scale actin filaments across micron-scale cell leading edges. It remains unclear how such inherently noisy processes generate robust cellular behavior. We employed high-speed, high-resolution imaging of migrating neutrophil-like HL-60 cells to explore the fine-scale dynamic shape fluctuations that emerge and relax throughout the process of leading edge maintenance. We then developed a minimal stochastic model of the leading edge that is able to reproduce this stable relaxation behavior. Remarkably, we find that lamellipodial stability naturally emerges from the interplay between branched actin network growth and leading edge shape – with no additional feedback required – based on a synergy between membrane-proximal branching and lateral spreading of filaments. These results thus demonstrate a novel biological noise-suppression mechanism based entirely on system geometry. Furthermore, our model suggests that the Arp2/3-mediated ∼70-80º branching angle optimally smooths lamellipodial shape, addressing its long-mysterious conservation from protists to mammals.One sentence summaryAn experimental and computational investigation of fluctuation dynamics at the leading edge of motile cells demonstrates that the specific angular geometry of Arp2/3-mediated actin network branch formation lies at the core of a successful biological noise-suppression strategy.

scholarly journals A Critical Review of Supersonic Flow Control for High-Speed Applications

2021 ◽  
Vol 11 (15) ◽  
pp. 6899
Author(s):  
Abdul Aabid ◽  
Sher Afghan Khan ◽  
Muneer Baig
Keyword(s):  
Supersonic Flow ◽  
Flow Control ◽  
Active Control ◽  
Critical Review ◽  
High Speed ◽  
Passive Control ◽  
Control Method ◽  
Sudden Expansion ◽  
Control Approach ◽  
Cost Efficient

In high-speed fluid dynamics, base pressure controls find many engineering applications, such as in the automobile and defense industries. Several studies have been reported on flow control with sudden expansion duct. Passive control was found to be more beneficial in the last four decades and is used in devices such as cavities, ribs, aerospikes, etc., but these need additional control mechanics and objects to control the flow. Therefore, in the last two decades, the active control method has been used via a microjet controller at the base region of the suddenly expanded duct of the convergent–divergent (CD) nozzle to control the flow, which was found to be a cost-efficient and energy-saving method. Hence, in this paper, a systemic literature review is conducted to investigate the research gap by reviewing the exhaustive work on the active control of high-speed aerodynamic flows from the nozzle as the major focus. Additionally, a basic idea about the nozzle and its configuration is discussed, and the passive control method for the control of flow, jet and noise are represented in order to investigate the existing contributions in supersonic speed applications. A critical review of the last two decades considering the challenges and limitations in this field is expressed. As a contribution, some major and minor gaps are introduced, and we plot the research trends in this field. As a result, this review can serve as guidance and an opportunity for scholars who want to use an active control approach via microjets for supersonic flow problems.

scholarly journals CFD Simulation of a Hyperloop Capsule Inside a Low-Pressure Environment Using an Aerodynamic Compressor as Propulsion and Drag Reduction Method

2021 ◽  
Vol 11 (9) ◽  
pp. 3934
Author(s):  
Federico Lluesma-Rodríguez ◽  
Temoatzin González ◽  
Sergio Hoyas
Keyword(s):  
Shock Waves ◽  
Power Consumption ◽  
High Speed ◽  
Cfd Simulation ◽  
Aerodynamic Drag ◽  
Flow Behavior ◽  
Critical Conditions ◽  
Vehicle Speed ◽  
Blockage Ratio ◽  
The Cost

One of the most restrictive conditions in ground transportation at high speeds is aerodynamic drag. This is even more problematic when running inside a tunnel, where compressible phenomena such as wave propagation, shock waves, or flow blocking can happen. Considering Evacuated-Tube Trains (ETTs) or hyperloops, these effects appear during the whole route, as they always operate in a closed environment. Then, one of the concerns is the size of the tunnel, as it directly affects the cost of the infrastructure. When the tube size decreases with a constant section of the vehicle, the power consumption increases exponentially, as the Kantrowitz limit is surpassed. This can be mitigated when adding a compressor to the vehicle as a means of propulsion. The turbomachinery increases the pressure of part of the air faced by the vehicle, thus delaying the critical conditions on surrounding flow. With tunnels using a blockage ratio of 0.5 or higher, the reported reduction in the power consumption is 70%. Additionally, the induced pressure in front of the capsule became a negligible effect. The analysis of the flow shows that the compressor can remove the shock waves downstream and thus allows operation above the Kantrowitz limit. Actually, for a vehicle speed of 700 km/h, the case without a compressor reaches critical conditions at a blockage ratio of 0.18, which is a tunnel even smaller than those used for High-Speed Rails (0.23). When aerodynamic propulsion is used, sonic Mach numbers are reached above a blockage ratio of 0.5. A direct effect is that cases with turbomachinery can operate in tunnels with blockage ratios even 2.8 times higher than the non-compressor cases, enabling a considerable reduction in the size of the tunnel without affecting the performance. This work, after conducting bibliographic research, presents the geometry, mesh, and setup. Later, results for the flow without compressor are shown. Finally, it is discussed how the addition of the compressor improves the flow behavior and power consumption of the case.

scholarly journals Internal face finishing for a cooling channel using a fluid containing free abrasive grains

2021 ◽  
Author(s):  
Mitsugu Yamaguchi ◽  
Tatsuaki Furumoto ◽  
Shuuji Inagaki ◽  
Masao Tsuji ◽  
Yoshiki Ochiai ◽  
...  
Keyword(s):  
High Speed ◽  
Flow Behavior ◽  
Flow Simulation ◽  
Cooling Channel ◽  
H13 Steel ◽  
Channel Diameter ◽  
Abrasive Grains ◽  
Low Viscosity ◽  
Short Period ◽  
Internal Pressures

AbstractIn die-casting and injection molding, a conformal cooling channel is applied inside the dies and molds to reduce the cycle time. When the internal face of the channel is rough, both cooling performance and tool life are negatively affected. Many methods for finishing the internal face of such channels have been proposed. However, the effects of the channel diameter on the flow of a low-viscosity finishing media and its finishing characteristics for H13 steel have not yet been reported in the literature. This study addresses these deficiencies through the following: the fluid flow in a channel was computationally simulated; the flow behavior of abrasive grains was observed using a high-speed camera; and the internal face of the channel was finished using the flow of a fluid containing abrasive grains. The flow velocity of the fluid with the abrasive grains increases as the channel diameter decreases, and the velocity gradient is low throughout the channel. This enables reduction in the surface roughness for a short period and ensures uniform finishing in the central region of the channel; however, over polishing occurs owing to the centrifugal force generated in the entrance region, which causes the form accuracy of the channel to partially deteriorate. The outcomes of this study demonstrate that the observational finding for the finishing process is consistent with the flow simulation results. The flow simulation can be instrumental in designing channel diameters and internal pressures to ensure efficient and uniform finishing for such channels.

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