The Experts below are selected from a list of 1155 Experts worldwide ranked by ideXlab platform
Krishna Shankar - One of the best experts on this subject based on the ideXlab platform.
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investigation of unswept normal shock wave turbulent boundary layer interaction control
Journal of Aircraft, 2009Co-Authors: J. S. Couldrick, J. F. Milthorpe, S L Gai, Krishna ShankarAbstract:An analytical model for the unswept normal shock wave/turbulent-boundary-layer interaction control using an upstream and downstream unimorph piezoelectric flap actuator has been proposed. The amount of flap deflection controls the bleed/suction rate through a Plenum Chamber. The cavity allows rapid thickening of the boundary layer approaching a normal shock wave, which splits into a series of weaker shocks forming a lambda shock foot, leading to a reduction in the wave drag. The analysis provides an understanding of the control influences produced in an experimental investigation of an unswept normal shock wave/turbulent-boundary-layer interaction at a Mach number of 1.5. It has also been validated by application to the normal shock wave/boundary-layer interaction control system using mesoflaps for aeroelastic transpiration described in previous transonic/supersonic shock wave/ boundary-layer interaction studies.
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normal shock wave turbulent boundary layer interaction control using smart piezoelectric actuators
Aeronautical Journal, 2005Co-Authors: J. S. Couldrick, J. F. Milthorpe, S L Gai, Krishna ShankarAbstract:This paper looks at active control of the normal shock wave/turbulent boundary layer interaction (SBLI) using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a Plenum Chamber. The cavity allows rapid thickening of the boundary-layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, thus reducing wave drag. Active control allows optimisation of the interaction, as it would be capable of either positioning the control region around the original shock position using a series of unimorph flaps or fixing the shock position by controlling the rate of mass transfer. The level of control achieved by unimorph piezoelectric actuators is not large because of small amounts of deflection possible. It is believed that to provide optimal control a piezoelectric material, which can provide greater strain and hence higher amounts of deflection is needed. However, currently such a piezoelectric material is not commercially available.
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active control of normal shock wave turbulent boundary layer interaction using smart piezoelectric flap actuators
2nd AIAA Flow Control Conference, 2004Co-Authors: J. S. Couldrick, J. F. Milthorpe, H Babinsky, S L Gai, H A Holden, Krishna ShankarAbstract:This paper looks at active control of the normal shock wave/turbulent boundary layer interaction (SBLI) using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a Plenum Chamber. The cavity provides communication of signals across the shock, allowing rapid thickening of the boundary layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, reducing wave drag. Active control allows optimum control of the interaction, as it would be capable of positioning the control region around the original shock position and control the rate of mass transfer. © 2004 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
J. S. Couldrick - One of the best experts on this subject based on the ideXlab platform.
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investigation of unswept normal shock wave turbulent boundary layer interaction control
Journal of Aircraft, 2009Co-Authors: J. S. Couldrick, J. F. Milthorpe, S L Gai, Krishna ShankarAbstract:An analytical model for the unswept normal shock wave/turbulent-boundary-layer interaction control using an upstream and downstream unimorph piezoelectric flap actuator has been proposed. The amount of flap deflection controls the bleed/suction rate through a Plenum Chamber. The cavity allows rapid thickening of the boundary layer approaching a normal shock wave, which splits into a series of weaker shocks forming a lambda shock foot, leading to a reduction in the wave drag. The analysis provides an understanding of the control influences produced in an experimental investigation of an unswept normal shock wave/turbulent-boundary-layer interaction at a Mach number of 1.5. It has also been validated by application to the normal shock wave/boundary-layer interaction control system using mesoflaps for aeroelastic transpiration described in previous transonic/supersonic shock wave/ boundary-layer interaction studies.
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normal shock wave turbulent boundary layer interaction control using smart piezoelectric actuators
Aeronautical Journal, 2005Co-Authors: J. S. Couldrick, J. F. Milthorpe, S L Gai, Krishna ShankarAbstract:This paper looks at active control of the normal shock wave/turbulent boundary layer interaction (SBLI) using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a Plenum Chamber. The cavity allows rapid thickening of the boundary-layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, thus reducing wave drag. Active control allows optimisation of the interaction, as it would be capable of either positioning the control region around the original shock position using a series of unimorph flaps or fixing the shock position by controlling the rate of mass transfer. The level of control achieved by unimorph piezoelectric actuators is not large because of small amounts of deflection possible. It is believed that to provide optimal control a piezoelectric material, which can provide greater strain and hence higher amounts of deflection is needed. However, currently such a piezoelectric material is not commercially available.
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active control of normal shock wave turbulent boundary layer interaction using smart piezoelectric flap actuators
2nd AIAA Flow Control Conference, 2004Co-Authors: J. S. Couldrick, J. F. Milthorpe, H Babinsky, S L Gai, H A Holden, Krishna ShankarAbstract:This paper looks at active control of the normal shock wave/turbulent boundary layer interaction (SBLI) using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a Plenum Chamber. The cavity provides communication of signals across the shock, allowing rapid thickening of the boundary layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, reducing wave drag. Active control allows optimum control of the interaction, as it would be capable of positioning the control region around the original shock position and control the rate of mass transfer. © 2004 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
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design of smart flap actuators for swept shock wave turbulent boundary layer interaction control
Structural Engineering and Mechanics, 2003Co-Authors: J. S. Couldrick, Krishnakumar Shankar, J. F. MilthorpeAbstract:Piezoelectric actuators have long been recognised for use in aerospace structures for control of structural shape. This paper looks at active control of the swept shock wave/turbulent boundary layer interaction using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a Plenum Chamber. The cavity provides communication of signals across the shock, allowing rapid thickening of the boundary layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, reducing wave drag. Active control allows optimum control of the interaction, as it would be capable of positioning the control region around the original shock position and unimorph tip deflection, hence mass transfer rates. The actuators are modelled using classical composite material mechanics theory, as well as a finite element-modelling program (ANSYS 5.7).
J. F. Milthorpe - One of the best experts on this subject based on the ideXlab platform.
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investigation of unswept normal shock wave turbulent boundary layer interaction control
Journal of Aircraft, 2009Co-Authors: J. S. Couldrick, J. F. Milthorpe, S L Gai, Krishna ShankarAbstract:An analytical model for the unswept normal shock wave/turbulent-boundary-layer interaction control using an upstream and downstream unimorph piezoelectric flap actuator has been proposed. The amount of flap deflection controls the bleed/suction rate through a Plenum Chamber. The cavity allows rapid thickening of the boundary layer approaching a normal shock wave, which splits into a series of weaker shocks forming a lambda shock foot, leading to a reduction in the wave drag. The analysis provides an understanding of the control influences produced in an experimental investigation of an unswept normal shock wave/turbulent-boundary-layer interaction at a Mach number of 1.5. It has also been validated by application to the normal shock wave/boundary-layer interaction control system using mesoflaps for aeroelastic transpiration described in previous transonic/supersonic shock wave/ boundary-layer interaction studies.
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normal shock wave turbulent boundary layer interaction control using smart piezoelectric actuators
Aeronautical Journal, 2005Co-Authors: J. S. Couldrick, J. F. Milthorpe, S L Gai, Krishna ShankarAbstract:This paper looks at active control of the normal shock wave/turbulent boundary layer interaction (SBLI) using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a Plenum Chamber. The cavity allows rapid thickening of the boundary-layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, thus reducing wave drag. Active control allows optimisation of the interaction, as it would be capable of either positioning the control region around the original shock position using a series of unimorph flaps or fixing the shock position by controlling the rate of mass transfer. The level of control achieved by unimorph piezoelectric actuators is not large because of small amounts of deflection possible. It is believed that to provide optimal control a piezoelectric material, which can provide greater strain and hence higher amounts of deflection is needed. However, currently such a piezoelectric material is not commercially available.
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active control of normal shock wave turbulent boundary layer interaction using smart piezoelectric flap actuators
2nd AIAA Flow Control Conference, 2004Co-Authors: J. S. Couldrick, J. F. Milthorpe, H Babinsky, S L Gai, H A Holden, Krishna ShankarAbstract:This paper looks at active control of the normal shock wave/turbulent boundary layer interaction (SBLI) using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a Plenum Chamber. The cavity provides communication of signals across the shock, allowing rapid thickening of the boundary layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, reducing wave drag. Active control allows optimum control of the interaction, as it would be capable of positioning the control region around the original shock position and control the rate of mass transfer. © 2004 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
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design of smart flap actuators for swept shock wave turbulent boundary layer interaction control
Structural Engineering and Mechanics, 2003Co-Authors: J. S. Couldrick, Krishnakumar Shankar, J. F. MilthorpeAbstract:Piezoelectric actuators have long been recognised for use in aerospace structures for control of structural shape. This paper looks at active control of the swept shock wave/turbulent boundary layer interaction using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a Plenum Chamber. The cavity provides communication of signals across the shock, allowing rapid thickening of the boundary layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, reducing wave drag. Active control allows optimum control of the interaction, as it would be capable of positioning the control region around the original shock position and unimorph tip deflection, hence mass transfer rates. The actuators are modelled using classical composite material mechanics theory, as well as a finite element-modelling program (ANSYS 5.7).
S L Gai - One of the best experts on this subject based on the ideXlab platform.
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investigation of unswept normal shock wave turbulent boundary layer interaction control
Journal of Aircraft, 2009Co-Authors: J. S. Couldrick, J. F. Milthorpe, S L Gai, Krishna ShankarAbstract:An analytical model for the unswept normal shock wave/turbulent-boundary-layer interaction control using an upstream and downstream unimorph piezoelectric flap actuator has been proposed. The amount of flap deflection controls the bleed/suction rate through a Plenum Chamber. The cavity allows rapid thickening of the boundary layer approaching a normal shock wave, which splits into a series of weaker shocks forming a lambda shock foot, leading to a reduction in the wave drag. The analysis provides an understanding of the control influences produced in an experimental investigation of an unswept normal shock wave/turbulent-boundary-layer interaction at a Mach number of 1.5. It has also been validated by application to the normal shock wave/boundary-layer interaction control system using mesoflaps for aeroelastic transpiration described in previous transonic/supersonic shock wave/ boundary-layer interaction studies.
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normal shock wave turbulent boundary layer interaction control using smart piezoelectric actuators
Aeronautical Journal, 2005Co-Authors: J. S. Couldrick, J. F. Milthorpe, S L Gai, Krishna ShankarAbstract:This paper looks at active control of the normal shock wave/turbulent boundary layer interaction (SBLI) using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a Plenum Chamber. The cavity allows rapid thickening of the boundary-layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, thus reducing wave drag. Active control allows optimisation of the interaction, as it would be capable of either positioning the control region around the original shock position using a series of unimorph flaps or fixing the shock position by controlling the rate of mass transfer. The level of control achieved by unimorph piezoelectric actuators is not large because of small amounts of deflection possible. It is believed that to provide optimal control a piezoelectric material, which can provide greater strain and hence higher amounts of deflection is needed. However, currently such a piezoelectric material is not commercially available.
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active control of normal shock wave turbulent boundary layer interaction using smart piezoelectric flap actuators
2nd AIAA Flow Control Conference, 2004Co-Authors: J. S. Couldrick, J. F. Milthorpe, H Babinsky, S L Gai, H A Holden, Krishna ShankarAbstract:This paper looks at active control of the normal shock wave/turbulent boundary layer interaction (SBLI) using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a Plenum Chamber. The cavity provides communication of signals across the shock, allowing rapid thickening of the boundary layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, reducing wave drag. Active control allows optimum control of the interaction, as it would be capable of positioning the control region around the original shock position and control the rate of mass transfer. © 2004 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
Grimshaw Sam - One of the best experts on this subject based on the ideXlab platform.
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Loss in Axial Compressor Bleed Systems
'Organisation for Economic Co-Operation and Development (OECD)', 2020Co-Authors: Grimshaw Sam, Brind James, Pullan G, Seki RAbstract:Loss in axial compressor bleed systems is quantified, and the loss mechanisms identified, in order to determine how efficiency can be improved. For a given bleed air pressure requirement, reducing bleed system loss allows air to be bled from further upstream in the compressor, with benefits for the thermodynamic cycle. A definition of isentropic efficiency which includes bleed flow is used to account for this. Two cases with similar bleed systems are studied: a low-speed, single-stage research compressor and a large industrial gas turbine high-pressure compressor. A new method for characterising bleed system loss is introduced, using research compressor test results as a demonstration case. A loss coefficient is defined for a control volume including only flow passing through the bleed system. The coefficient takes a measured value of 95% bleed system inlet dynamic head, and is shown to be a weak function of compressor operating point and bleed rate, varying by +/-2.2% over all tested conditions. This loss coefficient is the correct non-dimensional metric for quantifying and comparing bleed system performance. Computations of the research compressor and industrial gas turbine compressor identify the loss mechanisms in the bleed system flow. In both cases, approximately two-thirds of total loss is due to shearing of a high-velocity jet at the rear face of the bleed slot, one quarter is due to mixing in the Plenum Chamber and the remainder occurs in the off-take duct. Therefore, the main objective of a designer should be to diffuse the flow within the bleed slot. A redesigned bleed slot geometry is presented that achieves this objective and reduces the loss coefficient by 31%.Mitsubishi Heavy Industrie
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Bleed-induced distortion in axial compressors
Journal of Turbomachinery, 2015Co-Authors: Grimshaw Sam, Pullan Graham, Walker TAbstract:In this paper, the influence of nonuniform bleed extraction on the stability of an axial flow compressor is quantified. Nonuniformity can be caused by several geometric factors (for example, Plenum Chamber size or number of off-take ducts), and a range of configurations is examined experimentally in a single stage compressor. It is shown that nonuniform bleed leads to a circumferential distribution of flow coefficient and swirl angle at inlet to the downstream stage. The resultant distribution of rotor incidence causes stall to occur at a higher flow coefficient than if the same total bleed rate had been extracted uniformly around the circumference. A connection is made between the analysis of nonuniform bleed extraction and the familiar DCθ criterion used to characterize inlet total pressure distortion. The loss of operating range caused by the nonuniform inlet flow correlates with the peak sector-averaged bleed nonuniformity for all the bleed configurations tested.This is a metadata record relating to an article that cannot be shared due to publisher copyright
