The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Peiqing Liu - One of the best experts on this subject based on the ideXlab platform.
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near field Wingtip vortex characteristics of a Rectangular Wing in ground effect
54th AIAA Aerospace Sciences Meeting, 2016Co-Authors: Ramesh K Agarwal, Liewei Huang, Peiqing LiuAbstract:The aerodynamics and near-field Wingtip vortex characteristics of a Rectangular Wing with NACA4412 section in ground effect (GE) are studied in this paper. The steady compressible Reynolds-Averaged Navier-Stokes (RANS) equations with the SpalartAllmaras (SA) turbulence model are discretized using the finite volume method. Based on the pressure and lift variations in GE, a 3D Rectangular Wing can be divided into two parts along the span-wise direction: the quasi-2D inner part of the Wing (away from Wing tip) in which the lift increases monotonously, and the second part near the Wingtip in which the lift decreases. In GE, the Wingtip vortex moves outward along the span-wise direction due to the ground mirror effect, and rebounds in the vertical direction due to the induction from the secondary vortex generated from the ground boundary layer. In GE, the strength of the near-field Wingtip vortex along the flow direction depends not only on the initial vortex strength and the shear layer developing from the trailing edge of the Wing, but also due to the generation of secondary vortex in the ground boundary layer, and the interaction between the Wingtip vortex and the secondary vortex.
Youxin Zheng - One of the best experts on this subject based on the ideXlab platform.
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near field of the tip vortex behind an oscillating Rectangular Wing
AIAA Journal, 1998Co-Authors: B R Ramaprian, Youxin ZhengAbstract:were performed in a low-speed wind tunnel at a Reynolds number of 1 :8 £ 10 5 . The Wing had a semiaspect ratio of 2. It was oscillated at a frequency of 1 Hz and an amplitude of 5 deg around a mean incidence of 10 deg. The instantaneous LDV data were used to obtain information on the distribution of phase-locked velocity and vorticity components across the vortex, as well as the phase-locked circulation associated with the evolving vortex. The data indicate that the average trajectory of the oscillating vortex in the near e eld is very nearly the same as for a stationary Wing at the mean incidence. The length and circulation scales, as well as the maximum circulation carried by the vortex e ow under the conditions studied, are modulated in a signie cantly nonquasisteady manner. Nevertheless, beyond about 0.7 chordlength, the normalized circulation distribution across most of the inner part of the vortex exhibits, at all times, the same universal behavior as the vortex behind a stationary Wing.
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measurements in rollup region of the tip vortex from a Rectangular Wing
AIAA Journal, 1997Co-Authors: B R Ramaprian, Youxin ZhengAbstract:The evolving three-dimensional flowfield of the tip vortex in the near wake of a Rectangular Wing at incidence was studied in detail, using three-component laser Doppler velocimetry. The flow quantities measured were the three components of the instantaneous velocity. These data were used to obtain the distributions of velocity, vorticity, and circulation across the vortex at several axial locations in the flow for several angles of incidence. The data have been used to understand the process of rollup of the shear layer into the vortex in the near wake, as well as its kinematic structure. The data indicate that the rollup takes place quite quickly and the inner part of the three-dimensional vortex becomes nearly axisymmetric within a distance of about two chord lengths downstream of the trailing edge. Even though the vortex behavior in the near wake is, in general, strongly dependent on the initial conditions, the vortex trajectory appears to be described reasonably well by the overall Wing lift and the freestream velocity. Also, even in the near wake, circumferentially averaged mean flow properties in the inner part of the nearly axisymmetric vortex begin to exhibit a universal structure characteristic of conceptual asymptotic trailing vortices
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an experimental study of Wing tip vortex in the near wake of a Rectangular Wing
1993Co-Authors: Youxin Zheng, B R RamaprianAbstract:Abstract : An experimental study of the tip vortex behind a NACA 0015 Rectangular Wing of aspect ratio 4 was carried out to understand the structure and evolution of the vortex in the near-wake region. The results of these experimental studies are presented in this report. These measurements were made nonintrusively using three-component laser-Doppler velocimetry (LDV). The experiments were carried out at a Reynolds number of about 180,000 in a low- speed wind tunnel. Two cases were studied, namely, (1) stationary Wing and (2) Wing oscillating in pitch sinusoidally about its quarter-chord axis. The flow properties measured were the three components of the instantaneous velocity. These data were processed to obtain time-mean and phase-locked flow properties such as velocity, vorticity and turbulence. The data were obtained at several locations at 0.15 - 3.0 chord lengths downstream from the trailing edge. The typical distributions of mean velocity, vorticity, circulation and turbulent intensity in the near wake are presented and discussed for the stationary Wing. In the case of the oscillating Wing, the phase-locked velocity, vorticity and turbulence data show details of the evolution of the unsteady tip vortex downstream from the trailing edge. The results also show that the flow is strongly non-quasi-steady at the oscillation frequency studied. The results are fully archived on tape and are available to any interested reader. These can be used as database in the development of wake models for the finite Wing, and in studies of three-dimensional Wing aerodynamics.
B R Ramaprian - One of the best experts on this subject based on the ideXlab platform.
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near field of the tip vortex behind an oscillating Rectangular Wing
AIAA Journal, 1998Co-Authors: B R Ramaprian, Youxin ZhengAbstract:were performed in a low-speed wind tunnel at a Reynolds number of 1 :8 £ 10 5 . The Wing had a semiaspect ratio of 2. It was oscillated at a frequency of 1 Hz and an amplitude of 5 deg around a mean incidence of 10 deg. The instantaneous LDV data were used to obtain information on the distribution of phase-locked velocity and vorticity components across the vortex, as well as the phase-locked circulation associated with the evolving vortex. The data indicate that the average trajectory of the oscillating vortex in the near e eld is very nearly the same as for a stationary Wing at the mean incidence. The length and circulation scales, as well as the maximum circulation carried by the vortex e ow under the conditions studied, are modulated in a signie cantly nonquasisteady manner. Nevertheless, beyond about 0.7 chordlength, the normalized circulation distribution across most of the inner part of the vortex exhibits, at all times, the same universal behavior as the vortex behind a stationary Wing.
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measurements in rollup region of the tip vortex from a Rectangular Wing
AIAA Journal, 1997Co-Authors: B R Ramaprian, Youxin ZhengAbstract:The evolving three-dimensional flowfield of the tip vortex in the near wake of a Rectangular Wing at incidence was studied in detail, using three-component laser Doppler velocimetry. The flow quantities measured were the three components of the instantaneous velocity. These data were used to obtain the distributions of velocity, vorticity, and circulation across the vortex at several axial locations in the flow for several angles of incidence. The data have been used to understand the process of rollup of the shear layer into the vortex in the near wake, as well as its kinematic structure. The data indicate that the rollup takes place quite quickly and the inner part of the three-dimensional vortex becomes nearly axisymmetric within a distance of about two chord lengths downstream of the trailing edge. Even though the vortex behavior in the near wake is, in general, strongly dependent on the initial conditions, the vortex trajectory appears to be described reasonably well by the overall Wing lift and the freestream velocity. Also, even in the near wake, circumferentially averaged mean flow properties in the inner part of the nearly axisymmetric vortex begin to exhibit a universal structure characteristic of conceptual asymptotic trailing vortices
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an experimental study of Wing tip vortex in the near wake of a Rectangular Wing
1993Co-Authors: Youxin Zheng, B R RamaprianAbstract:Abstract : An experimental study of the tip vortex behind a NACA 0015 Rectangular Wing of aspect ratio 4 was carried out to understand the structure and evolution of the vortex in the near-wake region. The results of these experimental studies are presented in this report. These measurements were made nonintrusively using three-component laser-Doppler velocimetry (LDV). The experiments were carried out at a Reynolds number of about 180,000 in a low- speed wind tunnel. Two cases were studied, namely, (1) stationary Wing and (2) Wing oscillating in pitch sinusoidally about its quarter-chord axis. The flow properties measured were the three components of the instantaneous velocity. These data were processed to obtain time-mean and phase-locked flow properties such as velocity, vorticity and turbulence. The data were obtained at several locations at 0.15 - 3.0 chord lengths downstream from the trailing edge. The typical distributions of mean velocity, vorticity, circulation and turbulent intensity in the near wake are presented and discussed for the stationary Wing. In the case of the oscillating Wing, the phase-locked velocity, vorticity and turbulence data show details of the evolution of the unsteady tip vortex downstream from the trailing edge. The results also show that the flow is strongly non-quasi-steady at the oscillation frequency studied. The results are fully archived on tape and are available to any interested reader. These can be used as database in the development of wake models for the finite Wing, and in studies of three-dimensional Wing aerodynamics.
Ramesh K Agarwal - One of the best experts on this subject based on the ideXlab platform.
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near field Wingtip vortex characteristics of a Rectangular Wing in ground effect
54th AIAA Aerospace Sciences Meeting, 2016Co-Authors: Ramesh K Agarwal, Liewei Huang, Peiqing LiuAbstract:The aerodynamics and near-field Wingtip vortex characteristics of a Rectangular Wing with NACA4412 section in ground effect (GE) are studied in this paper. The steady compressible Reynolds-Averaged Navier-Stokes (RANS) equations with the SpalartAllmaras (SA) turbulence model are discretized using the finite volume method. Based on the pressure and lift variations in GE, a 3D Rectangular Wing can be divided into two parts along the span-wise direction: the quasi-2D inner part of the Wing (away from Wing tip) in which the lift increases monotonously, and the second part near the Wingtip in which the lift decreases. In GE, the Wingtip vortex moves outward along the span-wise direction due to the ground mirror effect, and rebounds in the vertical direction due to the induction from the secondary vortex generated from the ground boundary layer. In GE, the strength of the near-field Wingtip vortex along the flow direction depends not only on the initial vortex strength and the shear layer developing from the trailing edge of the Wing, but also due to the generation of secondary vortex in the ground boundary layer, and the interaction between the Wingtip vortex and the secondary vortex.
Youqing Wang - One of the best experts on this subject based on the ideXlab platform.
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numerical investigation of a finned tube heat exchanger with novel longitudinal vortex generators
Applied Thermal Engineering, 2015Co-Authors: Wenjin Wang, Yang Bao, Youqing WangAbstract:Abstract A novel longitudinal vortex generator (LVG), which is comprised of a modified Rectangular Wing and an accessory trapezoidal Wing, was proposed. The performance of finned-tube heat exchanger with a single row of novel combined Winglet pairs (NCWPs) was analyzed. Numerical simulation shows that compared with Rectangular Winglet pair (RWP), the NCWP generates main vortex with larger centric intensity. Furthermore, the accessory vortex has a lower core and flows into the back of tubes compressing wake regions' size behind tubes due to the influence of accessory Wing. It can disturb the developing of boundary layers on the bottom fin and enhance effectively the heat transfer of the wake region behind the tube. Therefore, the performance of heat transfer for finned-tube heat exchanger is significantly enhanced by NCWP with a moderate pressure drop penalty. Compared with the heat exchanger without LVGs, the heat transfer for finned-tube heat exchanger with NCWPs is improved by 1.8–24.2%, with a pressure penalty increase of 1.3–29.1%. In addition, theory analysis and numerical simulation well agree with the experiment results, indicating the reliability of the research.
