Experimental Investigation on the Effectiveness of Active Control Mechanism on Base Pressure at Low Supersonic Mach Numbers

Use of micro jets as an active control mechanism to control the base pressure in suddenly expanded flow from the C-D nozzle exhausted to the duct is investigated in this article. Experimental analysis is carried out at sonic Mach number and different nozzle pressure ratios. The enlarged diameter used in this investigation is 16 mm, 22.5 mm, and 27.5 mm. The length and diameter of the duct where the flow expands are also varied during the analysis. The role played by four micro jets of 1 mm diameter as an orifice to regulate the base pressure. The results as the percentage increase in base pressure are plotted for different level expansion and area ratio. For higher NPR = 7, the control significantly increases the base pressure without disturbing the wall pressure distribution. L/D = 3 and 4 seems to be optimum in resulting in a maximum increase in base pressure. For lower area ratio the minimum duct length required is L/D = 3, whereas for the highest area-ratio this limit is L/D = 4

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Effect of Area Ratio on Base Pressure in a Suddenly Expanded Duct for Under Expanded Flow ft Mach 1.87

International Journal of Mechanical and Industrial Engineering ◽

10.47893/ijmie.2013.1094 ◽

2013 ◽

pp. 198-202

Author(s):

M. Ahmed Ali Baig ◽

Sher Afghan Khan ◽

Mohammad Yunus Khan

Keyword(s):

Experimental Investigation ◽

Mach Number ◽

Active Control ◽

Pressure Field ◽

Area Ratio ◽

Wall Pressure ◽

Base Pressure ◽

Air Injection ◽

Minimum Length ◽

Percent Increase

The results of an experimental investigation carried out to control the base pressure in a suddenly expanded axi-symmetric passage is presented in this paper. An active control in the form of micro jets is employed to control the base pressure. Air injection at four locations at the base, symmetric to the nozzle axis is used as the active control. The jet Mach number studied and the area ratios are 1.87, and 2.56, 3.24, 4.84, and 6.25. The L/D ratio is varied from 10 to 1. The experiments are conducted at a fixed level of under expansion (i.e. Pe/Pa = 1.5). In addition to base pressure, wall pressure field along the duct was also measured. As high as 80 percent increase in base pressure was achieved for certain combination of parameters of the present study. The minimum Length-todiameter ratio of the duct required is L/D = 2 for area ratios 6.25 and 4.84. Whereas, this requirement is L/D = 1 for area ratios 2.56 and 3.24.

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An Experimental Investigation of Base Pressure on a Body of Revolution at High Thrust Levels and Free Stream Mach Numbers of 1.5 to 2.87

10.21236/ad0875042 ◽

1970 ◽

Author(s):

Joseph C. Craft ◽

Charles E. Brazzel

Keyword(s):

Experimental Investigation ◽

Free Stream ◽

Base Pressure ◽

Body Of Revolution ◽

Mach Numbers ◽

High Thrust

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Experimental investigation on active control of flow around a finite-length square cylinder using dual synthetic jet

Journal of Wind Engineering and Industrial Aerodynamics ◽

10.1016/j.jweia.2021.104519 ◽

2021 ◽

Vol 210 ◽

pp. 104519

Author(s):

Shiqing Li ◽

Zhenbing Luo ◽

Xiong Deng ◽

Wenqiang Peng ◽

Zhiyong Liu

Keyword(s):

Experimental Investigation ◽

Active Control ◽

Finite Length ◽

Synthetic Jet ◽

Square Cylinder ◽

Control Of Flow

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Structural Control Considering Time Delay Effect

Transactions of the Canadian Society for Mechanical Engineering ◽

10.1139/tcsme-1985-0029 ◽

1985 ◽

Vol 9 (4) ◽

pp. 224-227 ◽

Cited By ~ 14

Author(s):

Mohamed Abdel-Rohman

Keyword(s):

Time Delay ◽

Active Control ◽

Theoretical Consideration ◽

Structural Control ◽

Control Mechanism ◽

Structural Response ◽

Delay Effect ◽

Numerical Example ◽

Control Forces ◽

Time Delay Effect

The time delay between measuring the structural response, and applying the designed active control forces may affect the controlled response of the structure if not taken into consideration. In this paper it is shown how to design the control forces to compensate for the delay effect. It is also shown that the time delay effect can be used as a criterion to judge the effectiveness of the proposed control mechanism. As an illustration of the theoretical consideration, a numerical example in which a tall building is controlled by means of active tendons is presented.

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