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.

Subsonic Flow Over Open Cavities: Part 2 — Passive Control Methods

2016 ◽  
Author(s):  
Weidong Shao ◽  
Jun Li
Keyword(s):  
Sound Pressure ◽  
Passive Control ◽  
Subsonic Flow ◽  
Dynamic Pressure ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Control Methods ◽  
Trailing Edge ◽  
Open Cavities ◽  
Sound Pressure Levels

A global description of the intrinsic instabilities of shear layer for further understanding of the aeroacoustical oscillation of subsonic flow over open cavities has been given in the companion paper. The needs to suppress dynamic pressure loads in open cavities play an important role in many aeronautical applications. Large eddy simulation (LES) of passive control methods including recessed leading edge step and sloping trailing edge wall arrangements is performed. The unsteady flow characteristics and aeroacoustical oscillation mechanism of baseline cavity are given in advance. Effects of both passive control methods on resonant frequency and sound pressure levels are demonstrated and analyzed. Recessed leading edge step tends to decrease the resonant Strouhal numbers and the maximal reduction of overall sound pressure levels (OASPL) reaches 8.5dB. Sloping trailing edge wall reduces OASPL by shifting down the impinging location on cavity back wall. The optimal reduction of OASPL arrives at 11dB when the angle of inclination is maximal. The drag induced by cavity flows is found to be highly correlated with dynamic loads on cavity walls.

Passive control of deep cavity shear layer flow at subsonic speed

2017 ◽  
Vol 95 (10) ◽  
pp. 894-899
Author(s):  
Mouhammad El Hassan ◽  
Laurent Keirsbulck
Keyword(s):  
Shear Layer ◽  
Passive Control ◽  
Control Method ◽  
Leading Edge ◽  
Layer Growth ◽  
Cavity Resonance ◽  
Passive Flow Control ◽  
Acoustic Coupling ◽  
Deep Cavity ◽  
Layer Flow

Passive control of the flow over a deep cavity at low subsonic velocity is considered in the present paper. The cavity length-to-depth aspect ratio is L/H = 0.2. particle image velocimetry (PIV) measurements characterized the flow over the cavity and show the influence of the control method on the cavity shear layer development. It is found that both the “cylinder” and the “shaped cylinder”, placed upstream from the cavity leading edge, result in the suppression of the aero-acoustic coupling and highly reduce the cavity noise. It should be noted that the vortical structures impinge at almost the same location near the cavity downstream corner with and without passive control. The present study allows to identify an innovative passive flow control method of cavity resonance. Indeed, the use of a “shaped cylinder” presents similar suppression of the cavity resonance as with the “cylinder” but with less impact on the cavity flow. The “shaped cylinder” results in a smaller shear layer growth than the cylinder. Velocity deficiency and turbulence levels are less pronounced using the “shaped cylinder”. The “cylinder” tends to diffuse the vorticity in the cavity shear layer and thus the location of the maximum vorticity is more affected as compared to the “shaped cylinder” control. The fact that the “shaped cylinder” is capable of suppressing the cavity resonance, despite the vortex shedding and the high frequency forcing being suppressed, is of high interest from fundamental and applied points of view.

Computational investigation and passive control of vehicle sunroof buffeting

2019 ◽  
Vol 26 (9-10) ◽  
pp. 747-756
Author(s):  
Yansong He ◽  
Quanzhou Zhang ◽  
Changfa An ◽  
Yong Wang ◽  
Zhongming Xu ◽  
...  
Keyword(s):  
Flow Field ◽  
Passive Control ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Simulation Method ◽  
Dynamics Simulation ◽  
The Road ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Utility Vehicle

A computational fluid dynamics simulation method based on large eddy simulation is presented and applied to compute the sunroof buffeting of a sport utility vehicle. The simulation result, i.e. the buffeting level curve, coincides well with the road test. The simulation method is then employed to investigate the sunroof buffeting of a vehicle during the development process in the range of 30 km/h–90 km/h. The results show that the most severe sunroof buffeting occurs at 70 km/h, which corresponds to the resonant frequency of the cabin. Flow field visualizations reveal that strong pressure fluctuations are generated inside the cabin due to vortex shedding from the leading edge and impinging onto the trailing edge of the sunroof opening, which explains the mechanism of sunroof buffeting. A new deflector with a gap and a notched upper edge is designed to replace the original castle type deflector. The simulation results show that the newly designed deflector can reduce the buffeting level to 97.9 dB; that is, the sunroof buffeting is completely eliminated. Moreover, the phenomenon of sunroof buffeting reduction is explained by comparing and analyzing the flow field between the newly designed deflector and the original deflector.

scholarly journals Chaos Control and Anticontrol of the Output Duopoly Competing Evolution Model

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Zhaoqing Li ◽  
Yongping Zhang ◽  
Tongqian Zhang
Keyword(s):  
Social Development ◽  
Chaotic System ◽  
Chaos Control ◽  
Passive Control ◽  
Control Method ◽  
Evolution Model ◽  
Control Methods ◽  
Passive System ◽  
Optimal Function

In the process of social development, there are a lot of competitions and confrontations. Participants in these competitions and confrontations always have different interests and goals. In order to achieve their goals, the participants must consider the opponent’s strategy to adjust their own strategies to achieve the interests of the optimization. This is called game. Based on the definition and its stability of the passive system, the passive control items are designed to the output of the duopoly competition evolution model, and the efficacy of the control methods is shown by the Lyapunov indexes. Then, the optimal function control method is taken to carry on the chaotic anticontrol to the chaotic system, and the Lyapunov indexes illustrate the control result. At last, the chaotic game of the system is introduced by combining the chaos control and anticontrol.

The Optimal Control Method of Impulse Response in Prosthetic Leg

2014 ◽  
Vol 915-916 ◽  
pp. 1181-1185
Author(s):  
Xin Yi Xiao ◽  
Han Bin Xiao
Keyword(s):  
Optimal Control ◽  
Active Control ◽  
Impulse Response ◽  
Passive Control ◽  
Control Method ◽  
Control Variable ◽  
The Body ◽  
Control Techniques ◽  
Suspension Systems ◽  
Optimal Control Method

Passive control and semi-active control of vibration in mechanical systems have recently successfully been used in automobiles and airplanes suspension systems. These control techniques are able to guarantee the performances of all vibration structures. Unfortunately, the knowledge and data has not been readily applied to human prosthetics. The information collected can be directly applied to accelerate research into dampening for prosthetics. A focus of this paper is on modeling and controlling vibrations by a given impulse onto prosthetic legs. Simulations of using passive control and idealized skyhook dampening are using Matlab to complete. Through model analysis, control variable, simulation procedures and comparison of two modeling, the models have been refined and with idealized skyhook dampening suspension provide significant improvement of the body characteristics compared with passive suspensions.

scholarly journals Characterization of the aircraft bay/landing gear coupling noise at low subsonic speeds and its suppression using leading-edge chevron spoiler

2019 ◽  
Vol 11 (8) ◽  
pp. 168781401987143 ◽  
Author(s):  
Kun Zhao ◽  
Yong Liang ◽  
Tingrui Yue ◽  
Zhengwu Chen ◽  
Gareth J Bennett
Keyword(s):  
Shear Layer ◽  
Large Scale ◽  
Passive Control ◽  
Control Method ◽  
Leading Edge ◽  
Landing Gear ◽  
Pressure Transducers ◽  
Coupling Noise ◽  
Image Velocimetry

When the aircraft opens the bay door to let the landing gear either drop or retract, the incoming flow will result in a significant amount of coupling noise from the bay and the landing gear. Here, an experimental study was reported to characterise the acoustic performance and flow field at low subsonic speeds. Also, we examined a passive control method leading-edge chevron spoiler to suppress the noise. The experiment was performed in a low-speed aeroacoustic wind, the bay was simplified as a rectangular cavity and the spoiler was mounted to the leading edge. Both acoustic and aerodynamic measurements were performed through two microphone arrays, pressure transducers and particle image velocimetry. It was found that installation of the landing gear model can attenuate cavity oscillation noise to some extent by disturbing the shear layer of the cavity leading edge. Moreover, acoustic measurement confirmed the noise control when the spoiler was used. In addition, a parametric study on the effects of chevron topology was performed, and an optimised value was found for each parameter. From the aerodynamic measurement, the noise reduction was explained from the perspective of fluid dynamics. It was observed that installation of the chevron can raise the leading-edge shear layer and break up the large-scale vortices, thereby controlling the Rossiter mode noise and the landing gear model noise at certain frequencies.

scholarly journals Experimental Investigation of Rotor-Stator Interaction in a Centrifugal Pump With Several Vaned Diffusers

1989 ◽  
Author(s):  
N. Arndt ◽  
A. J. Acosta ◽  
C. E. Brennen ◽  
T. K. Caughey
Keyword(s):  
Pressure Fluctuations ◽  
Leading Edge ◽  
Maximum Flow ◽  
Suction Side ◽  
Flow Coefficient ◽  
Pressure Measurements ◽  
Two Dimensional ◽  
Trailing Edge ◽  
Impeller Blade ◽  
Rotor Stator Interaction

This paper describes an experimental investigation of rotor–stator interaction in a centrifugal pump with several vaned diffusers. Steady and unsteady diffuser vane pressure measurements were made for a two–dimensional test impeller. Unsteady impeller blade pressure measurements were made for a second two–dimensional impeller with blade number and blade geometry identical to the two–dimensional impeller used for the diffuser vane pressure measurements. The experiments were conducted for different flow coefficients and different radial gaps between the impeller blade trailing edge and the diffuser vane leading edge (5% and 8% of the impeller discharge radius). The largest pressure fluctuations on the diffuser vanes and the impeller blades were found to be of the same order of magnitude as the total pressure rise across the pump. The largest pressure fluctuations on the diffuser vanes were observed to occur on the suction side of the vane near the vane leading edge, whereas on the impeller blades the largest fluctuations were observed to occur at the blade trailing edge. However, the dependence of the fluctuations on the flow coefficient was found to be different for the diffuser vanes and the impeller blades; on the vane suction side, the fluctuations were largest for the maximum flow coefficient and decreased with decreasing flow coefficient, whereas at the blade trailing edge, the fluctuations were smallest for the maximum flow coefficient and increased with decreasing flow coefficient. Increasing the number of the diffuser vanes resulted in a significant decrease of the impeller blade pressure fluctuations. The resulting lift on the diffuser vanes was computed from the vane pressure measurements; the magnitude of the fluctuating lift was found to be larger than the steady lift.

Experimental Analysis of an Axial Inducer Influence of the Shape of the Blade Leading Edge on the Performances in Cavitating Regime

2003 ◽  
Vol 125 (2) ◽  
pp. 293-301 ◽  
Author(s):  
F. Bakir ◽  
S. Kouidri ◽  
R. Noguera ◽  
R. Rey
Keyword(s):  
Experimental Analysis ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Cavitation Number ◽  
Experimental Results ◽  
Test Rig ◽  
Cfd Simulations ◽  
Trailing Edge ◽  
Flow Rates ◽  
Blade Leading Edge

The aim of this paper is to analyze, from experimental results, the influence of the shape of the leading edge and its sharpening on the cavitating behavior of an inducer. The studied inducer is designed according to a methodology developed at LEMFI. Successive cutting and sharpening (four cuts, which modify up to 20 percent of the blade chord at the tip), were made to modify the shape of the leading edge. For the various geometries, the experimental results obtained on the LEMFI test rig are presented as follows. Noncavitating Regime: Overall performances at 1450 rpm. Cavitating Regime: (1) The development of the cavitation versus the cavitation number, (2) the description of the various cavitation pictures, and (3) the pressure fluctuations measured at the wall at 150 mm downstream of the trailing edge for various flow rates and inlet pressures. The CFD simulations carried out under CFX-Blade Gen+ on this range of inducers are presented to explain certain aspects observed.

scholarly journals An active control method for reducing sonic boom of supersonic aircraft

2021 ◽  
Vol 39 (3) ◽  
pp. 566-575
Author(s):  
Liuqing Ye ◽  
Zhengyin Ye ◽  
Boping Ma
Keyword(s):  
Mass Flow Rate ◽  
Active Control ◽  
Mass Flow ◽  
Flow Rate ◽  
Control Method ◽  
Leading Edge ◽  
Sonic Boom ◽  
Trailing Edge ◽  
Supersonic Aircraft ◽  
Active Control Method

Sonic boom reduction has been an urgent need to develop the future supersonic transport, because of the heavy damages of the noise pollution. This paper provides an active control method for the supersonic aircraft to reduce the sonic boom, wherein a suction slot near the leading edge and an injection slot near the trailing edge on the airfoil suction surface are opened, and the mass flow sucked in near the leading edge is equal to the mass flow injected near the trailing edge. The diamond and 566 airfoils are adopted as the baseline airfoil to verify the capability of the active control method, and the effects of the suction and injection location, the mass flow rate and the attack angle on the ground boom signature, the maximum overpressure, the drag coefficients and the ratio of lift to drag are studied in detail. The results show that the proposed active control method can significantly reduce the sonic boom, and the reduction of the sonic boom intensity is more sensitive to the injection near the trailing edge than the suction near the leading edge. Applying this active control method to the diamond (NACA0008) airfoil, when the mass flow rate is 6.5 kg/s(7.5 kg/s), the value of maximum positive overpressure is decreased by 12.87%(12.85%), the value of maximum negative overpressure is decreased by 33.83%(56.77%) and the drag coefficient is decreased by 9.50%(10.96%). It can be seen that the method proposed in this paper has great benefits in the reduction of sonic boom and provides a useful reference for designing a new generation of lower sonic boom supersonic aircraft.

scholarly journals Experimental Investigation of Rotor-Stator Interaction in a Centrifugal Pump With Several Vaned Diffusers

1990 ◽  
Vol 112 (1) ◽  
pp. 98-108 ◽  
Author(s):  
N. Arndt ◽  
A. J. Acosta ◽  
C. E. Brennen ◽  
T. K. Caughey
Keyword(s):  
Pressure Fluctuations ◽  
Leading Edge ◽  
Maximum Flow ◽  
Suction Side ◽  
Flow Coefficient ◽  
Pressure Measurements ◽  
Two Dimensional ◽  
Trailing Edge ◽  
Impeller Blade ◽  
Rotor Stator Interaction

This paper describes an experimental investigation of rotor-stator interaction in a centrifugal pump with several vaned diffusers. Steady and unsteady diffuser vane pressure measurements were made for a two-dimensional test impeller. Unsteady impeller blade pressure measurements were made for a second two-dimensional impeller with blade number and blade geometry identical to the two-dimensional impeller used for the diffuser vane pressure measurements. The experiments were conducted for different flow coefficients and different radial gaps between the impeller blade trailing edge and the diffuser vane leading edge (5 and 8 percent of the impeller discharge radius). The largest pressure fluctuations on the diffuser vanes and the impeller blades were found to be of the same order of magnitude as the total pressure rise across the pump. The largest pressure fluctuations on the diffuser vanes were observed to occur on the suction side of the vane near the vane leading edge, whereas on the impeller blades the largest fluctuations were observed to occur at the blade trailing edge. However, the dependence of the fluctuations on the flow coefficient was found to be different for the diffuser vanes and the impeller blades; on the vane suction side, the fluctuations were largest for the maximum flow coefficient and decreased with decreasing flow coefficient, whereas at the blade trailing edge, the fluctuations were smallest for the maximum flow coefficient and increased with decreasing flow coefficient. Increasing the number of the diffuser vanes resulted in a significant decrease of the impeller blade pressure fluctuations. The resulting lift on the diffuser vanes was computed from the vane pressure measurements; the magnitude of the fluctuating lift was found to be larger than the steady lift.

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