On the significance of unsteady effects in the aerodynamic performance of flying animals

1993 ◽  
pp. 401-419 ◽  
Author(s):  
G. Spedding
Keyword(s):  
Aerodynamic Performance ◽  
Unsteady Effects

Unsteady Effects of Blade Row Interaction on Flow Field and Aerodynamic Performance of a Transonic Centrifugal Compressor Impeller

2021 ◽  
Author(s):  
Kazutoyo Yamada ◽  
Kosuke Kubo ◽  
Kenichiro Iwakiri ◽  
Yoshihiro Ishikawa ◽  
Hirotaka Higashimori
Keyword(s):  
Steady State ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Aerodynamic Performance ◽  
Vaned Diffuser ◽  
Tip Leakage ◽  
Transonic Centrifugal Compressor ◽  
Compressor Performance ◽  
Unsteady Effects ◽  
Rans Analysis

Abstract This paper discusses the unsteady effects associated with the impeller/diffuser interaction on the internal flow field and aerodynamic performance of a centrifugal compressor. In centrifugal compressors with a vaned diffuser, the flow field is inherently unsteady due to the influence of interaction between the impeller and the diffuser, and the unsteadiness of the flow field can often have a great influence on the aerodynamic performance of the compressor. Especially in high-load compressors, it is considered that large unsteady effects are produced on the compressor performance with a strong flow unsteadiness. The unsteady effect on aerodynamic performance of the compressor has not been fully revealed yet, and sometimes the steady-state RANS simulation finds it difficult to predict the compressor performance. In this study, numerical simulations have been conducted for a transonic centrifugal compressor with a vaned diffuser. The unsteady effects were clarified by comparing the numerical results between a single-passage steady-state RANS analysis and a full-annulus unsteady RANS analysis. The comparison of simulation results showed the difference in entropy generation in the impeller. The impingement of diffuser shock wave with the impeller pressure surface brought about a cyclic increase in the blade loading near the impeller trailing edge. Accordingly, with increasing tip leakage flow rate, a second tip leakage vortex was newly generated in the aft part of the impeller, which resulted in additional unsteady loss generation inside the impeller.

Flapping wings in line formation flight: a computational analysis

2014 ◽  
Vol 118 (1203) ◽  
pp. 485-501 ◽  
Author(s):  
M. Ghommem ◽  
V. M. Calo
Keyword(s):  
Power Consumption ◽  
Aerodynamic Performance ◽  
Formation Flight ◽  
Flapping Wings ◽  
Line Formation ◽  
Lattice Method ◽  
Flow Solver ◽  
Vortex Lattice Method ◽  
Bird Evolution ◽  
Unsteady Effects

AbstractThe current understanding of the aerodynamics of birds in formation flights is mostly based on field observations. The interpretation of these observations is usually made using simplified aerodynamic models. Here, we investigate the aerodynamic aspects of formation flights. We use a potential flow solver based on the unsteady vortex lattice method (UVLM) to simulate the flow over flapping wings flying in grouping arrangements and in proximity of each other. UVLM has the capability to capture unsteady effects associated with the wake. We demonstrate the importance of properly capturing these effects to assess aerodynamic performance of flapping wings in formation flight. Simulations show that flying in line formation at adequate spacing enables significant increase in the lift and thrust and reduces power consumption. This is mainly due to the interaction between the trailing birds and the previously-shed wake vorticity from the leading bird. Moreover, enlarging the group of birds flying in formation further improves the aerodynamic performance for each bird in the flock. Therefore, birds get significant benefit of such organised patterns to minimise power consumption while traveling over long distances without stop and feeding. This justifies formation flight as being beneficial for bird evolution without regard to potential social benefits, such as, visual and communication factors for group protection and predator evasion.

Effects of stator splitter blades on aerodynamic performance of a single-stage transonic axial compressor

2020 ◽  
Vol 14 (4) ◽  
pp. 7369-7378
Author(s):  
Ky-Quang Pham ◽  
Xuan-Truong Le ◽  
Cong-Truong Dinh
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Aerodynamic Performance ◽  
Numerical Results ◽  
Single Stage ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Operating Stability ◽  
Length Coverage

Splitter blades located between stator blades in a single-stage axial compressor were proposed and investigated in this work to find their effects on aerodynamic performance and operating stability. Aerodynamic performance of the compressor was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations using the k-e turbulence model with a scalable wall function. The numerical results for the typical performance parameters without stator splitter blades were validated in comparison with experimental data. The numerical results of a parametric study using four geometric parameters (chord length, coverage angle, height and position) of the stator splitter blades showed that the operational stability of the single-stage axial compressor enhances remarkably using the stator splitter blades. The splitters were effective in suppressing flow separation in the stator domain of the compressor at near-stall condition which affects considerably the aerodynamic performance of the compressor.

Numerical Study of the Roughness Influence on NACA 63-430 Profile Aerodynamic Performance

2016 ◽  
Vol 10 (4) ◽  
pp. 231
Author(s):  
Abdekarim Tebbal ◽  
Fethi Saidi ◽  
Boualem Noureddine ◽  
Bachir Imine ◽  
Benameur Hamoudi
Keyword(s):  
Numerical Study ◽  
Aerodynamic Performance

Aerodynamic Performance of a Helicopter Rotor Hovering in Close Proximity to the Obstacles with Penetration Boundary Condition

2016 ◽  
Vol 64 (1) ◽  
pp. 65-70
Author(s):  
Naohiro IBOSHI ◽  
Noriaki ITOGA ◽  
Yasuhide YAMANAKA ◽  
Abdul KADIR, ◽  
Yuzaburou HAYASHI ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Aerodynamic Performance ◽  
Helicopter Rotor ◽  
Close Proximity
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