Active Control of an Incompressible Axisymmetric Jet

2008 ◽  
Author(s):  
D. Greenblatt ◽  
Y. Singh ◽  
C. N. Nayeri ◽  
C. O. Paschereit ◽  
N. K. Depuru Mohan
Keyword(s):  
Experimental Investigation ◽  
Flow Control ◽  
Active Control ◽  
Jet Noise ◽  
Control Methods ◽  
Streamwise Vortices ◽  
Streamwise Vorticity ◽  
Propulsion Efficiency ◽  
Axisymmetric Jet ◽  
Active Generation

An experimental investigation was conducted to compare the active generation and management of streamwise vortices in an incompressible jet flow using different flow control methods. The lip of the jet was equipped with a small flap deflected away from the stream at an angle of 30°, that incorporated a flow control slot through which steady suction, oscillatory suction and zero mass-flux perturbations were introduced. Data acquired were compared on the basis of momentum addition to the jet, the generation of streamwise vorticity and the generation of turbulent stresses. All active control methods produced an increase in jet momentum, stronger streamwise vortices and higher turbulence levels than those produced by a simple tab. The increase in jet momentum, combined with the generation of strong streamwise vortices and elevated turbulence levels, indicates potential for improvements in propulsion efficiency, mixing and possibly jet noise reduction.

Active and Passive Flow Control of an Incompressible Axisymmetric Jet

2008 ◽  
Author(s):  
Nagendra Karthik Depuru Mohan ◽  
David Greenblatt ◽  
Christian Navid Nayeri ◽  
Christian Oliver Paschereit ◽  
Panchapakesan Nagangudy Ramamurthi
Keyword(s):  
Flow Control ◽  
Active Flow Control ◽  
Central Portion ◽  
Jet Stream ◽  
Streamwise Vortices ◽  
Passive Flow Control ◽  
Axisymmetric Jet ◽  
Passive Flow ◽  
Negative Pressures ◽  
Active Flow

An experimental investigation was carried out to compare active and passive flow control of an incompressible axisymmetric jet. For active flow control, the lip of the circular jet was equipped with a single small flap deflected away from the jet stream at an angle of 30°. The flap incorporated a flow control slot through which steady suction and oscillatory suction were implemented. For passive flow control, the lip of the circular jet was equipped with a single small triangular tab deflected into the jet stream at an angle of 30°. Both the flap and triangular tab chord lengths were one sixth of the jet diameter. The momentum of jet increased in the case of active flow control by entraining ambient fluid, whereas momentum decreased in the case of passive flow control. The effect of steady suction saturated for volumetric suction coefficient values greater than approximately 0.82%. The strength of the streamwise vortices generated by active flow control flaps were greater than those generated by the passive triangular tab. Steady suction produced positive pressures just downstream of the flow control slot in the central portion of the flap and negative pressures at the flap edges. Oscillatory suction was highly dependent on dimensionless frequency (F+) based on flap-length; the pressures on the central portion of the flap increased for F+≤0.11 and then decreased for greater F+; finally attaining negative pressures at F+ = 0.44. The increase in jet momentum, combined with the generation of strong streamwise vortices makes a strong case for improvements in propulsion efficiency and jet noise reduction.

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.

Experimental investigation of an active control casing treatment of centrifugal compressors

2017 ◽  
Vol 83 ◽  
pp. 107-117 ◽  
Author(s):  
Qichao Yang ◽  
Liansheng Li ◽  
Yuanyang Zhao ◽  
Jun Xiao ◽  
Yue Shu ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Active Control ◽  
Centrifugal Compressors ◽  
Casing Treatment

Active control of an axisymmetric jet with distributed electromagnetic flap actuators

2004 ◽  
Vol 36 (3) ◽  
pp. 498-509 ◽  
Author(s):  
H. Suzuki ◽  
N. Kasagi ◽  
Y. Suzuki
Keyword(s):  
Active Control ◽  
Axisymmetric Jet

Inlet Skew and the Growth of Secondary Losses and Vorticity in a Turbine Cascade

1989 ◽  
Author(s):  
J. A. Walsh ◽  
D. G. Gregory-Smith
Keyword(s):  
Experimental Investigation ◽  
Large Scale ◽  
Transverse Velocity ◽  
Axial Flow ◽  
Turbine Cascade ◽  
Streamwise Vorticity ◽  
Loss Prediction

This paper presents results of an experimental investigation into the effects of inlet skew on the flowfield of a large scale axial flow turbine cascade. The results are presented in terms of the development of the streamwise vorticity since, in classical terms, the streamwise vorticity generates the transverse velocity components that cause the generation of the secondary losses. Inlet skew is shown to have a profound effect on the distribution and magnitude of the generated losses. A number of correlations for the secondary losses are compared with the measured values and it is shown that the correlations are not adequate for accurate loss prediction purposes.

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