scholarly journals Quasi-Steady versus Navier–Stokes Solutions of Flapping Wing Aerodynamics

Fluids ◽  
2018 ◽  
Vol 3 (4) ◽  
pp. 81 ◽  
Author(s):  
Jeremy Pohly ◽  
James Salmon ◽  
James Bluman ◽  
Kabilan Nedunchezian ◽  
Chang-kwon Kang
Keyword(s):  
Stokes Equations ◽  
Aerodynamic Force ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Fruit Fly ◽  
Flapping Wing ◽  
Navier Stokes ◽  
Pitching Motion ◽  
Navier Stokes Equations ◽  
Wing Motion

Various tools have been developed to model the aerodynamics of flapping wings. In particular, quasi-steady models, which are considerably faster and easier to solve than the Navier–Stokes equations, are often utilized in the study of flight dynamics of flapping wing flyers. However, the accuracy of the quasi-steady models has not been properly documented. The objective of this study is to assess the accuracy of a quasi-steady model by comparing the resulting aerodynamic forces against three-dimensional (3D) Navier–Stokes solutions. The same wing motion is prescribed at a fruit fly scale. The pitching amplitude, axis, and duration are varied. Comparison of the aerodynamic force coefficients suggests that the quasi-steady model shows significant discrepancies under extreme pitching motions, i.e., the pitching motion is large, quick, and occurs about the leading or trailing edge. The differences are as large as 1.7 in the cycle-averaged lift coefficient. The quasi-steady model performs well when the kinematics are mild, i.e., the pitching motion is small, long, and occurs near the mid-chord with a small difference in the lift coefficient of 0.01. Our analysis suggests that the main source for the error is the inaccuracy of the rotational lift term and the inability to model the wing-wake interaction in the quasi-steady model.

Aerodynamics of a two-dimensional flapping wing hovering in proximity of ground

2019 ◽  
Vol 233 (12) ◽  
pp. 4316-4332 ◽  
Author(s):  
Yunlong Zheng ◽  
Qiulin Qu ◽  
Peiqing Liu ◽  
Yunpeng Qin ◽  
Ramesh K Agarwal
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Aerodynamic Force ◽  
Ground Effect ◽  
Flapping Wing ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Navier Stokes Equations ◽  
Lift Mechanism ◽  
The Difference

The difference in aerodynamic forces of a two-dimensional flapping wing hovering in unbounded flow field and ground effect is studied. The unsteady laminar Navier–Stokes equations are solved by the finite volume method to simulate the flow field around the wing. In the unbounded flow field, the correspondence between the aerodynamic force, pressure distribution on wing, and typical vortex structures is established, and then the high-lift mechanism of the flapping wing is further explained. In the ground effect, based on the lift variation, the dimensionless height H/ C ( H is the height of the wing above ground and C is the chord length of the wing) can be divided into transition and ground effect regimes. In the transition regime ( H/ C > 2.5), the lift decreases with the decreasing height, and the ground indirectly impacts the vortices near wing by changing the shed vortices in space. In the ground effect regime ( H/ C < 2.5), the lift increases with the decreasing height, and the ground directly impacts the vortices near the wing.

Numerical Investigation of Self-Driven Fan Performance With Tip-Jet

2017 ◽  
Author(s):  
Lei Li ◽  
GuoPing Huang ◽  
Jie Chen ◽  
JinChun Wang
Keyword(s):  
Stokes Equations ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Suction Surface ◽  
Navier Stokes Equations ◽  
Momentum Coefficient ◽  
Aerodynamic Properties ◽  
Flow Phenomena ◽  
Cfd Method

Tip-jet rotor system has unique potential value in the area of vertical take-off and landing (VTOL) or short take-off and landing (STOL) concept aircraft. The main objective of the current work is to investigate the aerodynamic properties of a self-driven fan with tip-jet (SDF_TJ) in hover by numerical experiments. In order to obtain the detailed flow phenomena of SDF_TJ, CFD method is performed, which is conducted by solving three-dimensional Reynolds-averaged Navier-Stokes equations using the shear stress transport turbulence model. For the purpose of investigation, the analysis of SDF_TJ performances with different nozzle configurations have been carried out. Current results indicate the conformal tip-jet not only provide the reaction torque, but also augment the fan lift via entraining the main flow above the suction surface of blade. The rotation speed of fan is mainly determined by bleed air parameters and nozzle area, so as to torque self-balance. The total torque produced by jets contains rotor required torque and penalty torque induced by Coriolis force. The blade lift coefficient and the ratio with jet momentum coefficient are influenced by the distance from the nozzle downstream edge to blade trailing. As the lift of SDF_TJ is larger than the thrust generated by jets alone, which could benefit the take-off and landing capability of VTOL concept aircraft.

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.

Simulation of Unsteady Flow Around a Cylinder

2015 ◽  
Vol 3 (2) ◽  
pp. 28-49
Author(s):  
Ridha Alwan Ahmed
Keyword(s):  
Stokes Equations ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Mean Value ◽  
Navier Stokes ◽  
Cylinder Surface ◽  
Navier Stokes Equations ◽  
Flow Around A Cylinder ◽  
Numerical Grid ◽  
Good Agreement

       In this paper, the phenomena of vortex shedding from the circular cylinder surface has been studied at several Reynolds Numbers (40≤Re≤ 300).The 2D, unsteady, incompressible, Laminar flow, continuity and Navier Stokes equations have been solved numerically by using CFD Package FLUENT. In this package PISO algorithm is used in the pressure-velocity coupling.        The numerical grid is generated by using Gambit program. The velocity and pressure fields are obtained upstream and downstream of the cylinder at each time and it is also calculated the mean value of drag coefficient and value of lift coefficient .The results showed that the flow is strongly unsteady and unsymmetrical at Re>60. The results have been compared with the available experiments and a good agreement has been found between them

scholarly journals Dynamics of Single Droplet Splashing on Liquid Film by Coupling FVM with VOF

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 841
Author(s):  
Yuzhen Jin ◽  
Huang Zhou ◽  
Linhang Zhu ◽  
Zeqing Li
Keyword(s):  
Liquid Film ◽  
Weber Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Single Droplet ◽  
Navier Stokes Equations ◽  
Volume Method ◽  
The Relationship

A three-dimensional numerical study of a single droplet splashing vertically on a liquid film is presented. The numerical method is based on the finite volume method (FVM) of Navier–Stokes equations coupled with the volume of fluid (VOF) method, and the adaptive local mesh refinement technology is adopted. It enables the liquid–gas interface to be tracked more accurately, and to be less computationally expensive. The relationship between the diameter of the free rim, the height of the crown with different numbers of collision Weber, and the thickness of the liquid film is explored. The results indicate that the crown height increases as the Weber number increases, and the diameter of the crown rim is inversely proportional to the collision Weber number. It can also be concluded that the dimensionless height of the crown decreases with the increase in the thickness of the dimensionless liquid film, which has little effect on the diameter of the crown rim during its growth.

The inlet flow structure of a conceptual open-nose supersonic drone

2021 ◽  
pp. 095441002098304
Author(s):  
Eiman B Saheby ◽  
Xing Shen ◽  
Anthony P Hays ◽  
Zhang Jun
Keyword(s):  
Flow Structure ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Computational Fluid Dynamic Simulation ◽  
Navier Stokes ◽  
Ansys Fluent ◽  
Navier Stokes Equations ◽  
Aerodynamic Efficiency ◽  
Performance Effects

This study describes the aerodynamic efficiency of a forebody–inlet configuration and computational investigation of a drone system, capable of sustainable supersonic cruising at Mach 1.60. Because the whole drone configuration is formed around the induction system and the design is highly interrelated to the flow structure of forebody and inlet efficiency, analysis of this section and understanding its flow pattern is necessary before any progress in design phases. The compression surface is designed analytically using oblique shock patterns, which results in a low drag forebody. To study the concept, two inlet–forebody geometries are considered for Computational Fluid Dynamic simulation using ANSYS Fluent code. The supersonic and subsonic performance, effects of angle of attack, sideslip, and duct geometries on the propulsive efficiency of the concept are studied by solving the three-dimensional Navier–Stokes equations in structured cell domains. Comparing the results with the available data from other sources indicates that the aerodynamic efficiency of the concept is acceptable at supersonic and transonic regimes.

scholarly journals A Code for Simulating Heat Transfer in Turbulent Channel Flow

Mathematics ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 756
Author(s):  
Federico Lluesma-Rodríguez ◽  
Francisco Álcantara-Ávila ◽  
María Jezabel Pérez-Quiles ◽  
Sergio Hoyas
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Turbulent Channel Flow ◽  
Passive Scalar ◽  
Direct Numerical Simulations ◽  
Time Dependent ◽  
Navier Stokes ◽  
Thermal Flow ◽  
Navier Stokes Equations

One numerical method was designed to solve the time-dependent, three-dimensional, incompressible Navier–Stokes equations in turbulent thermal channel flows. Its originality lies in the use of several well-known methods to discretize the problem and its parallel nature. Vorticy-Laplacian of velocity formulation has been used, so pressure has been removed from the system. Heat is modeled as a passive scalar. Any other quantity modeled as passive scalar can be very easily studied, including several of them at the same time. These methods have been successfully used for extensive direct numerical simulations of passive thermal flow for several boundary conditions.

scholarly journals Implicit Weighted ENO Schemes for the Three-Dimensional Incompressible Navier–Stokes Equations

1998 ◽  
Vol 146 (1) ◽  
pp. 464-487 ◽  
Author(s):  
Jaw-Yen Yang ◽  
Shih-Chang Yang ◽  
Yih-Nan Chen ◽  
Chiang-An Hsu
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Eno Schemes ◽  
Weighted Eno
Sign in / Sign up

Export Citation Format

Share Document