Xueguang Meng¹, Zengshuang Chen¹, Yuxin Xie¹, Gang Chen^1,*

The International Conference on Computational & Experimental Engineering and Sciences, Vol.27, No.4, pp. 1-5, 2023, DOI:10.32604/icces.2023.09892

Abstract Many species generally choose highly organized movements to gain more performance advantages rather than alone in the animal world, such as V-formation and line formation in birds. Understanding the aerodynamic characteristics and flow variation of multi-flapping wings in formation flight could be applied to the formation design of new bionic flapping-wing aircraft. In this paper, the effects of unequal individual spacing on the aerodynamic performance and flow mechanism of three-dimensional three-flapping wings flying in tandem formation are investigated numerically at a low Reynolds number. The simulations include small and large spacings, as well as cases with equal and unequal spacings… More >

Zhaolin Chen^1,*, Xiaohui Wei¹, Tianhang Xiao¹, Ning Qin²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.25, No.2, pp. 1-1, 2023, DOI:10.32604/icces.2023.09976

Abstract A computational study has been conducted on various airfoils to simulate flows at low Reynolds numbers 17,000 and 21,000 with Mach number changes from 0.25 to 0.85 to provide understanding and guidance for Mars rotory wing designs. The computational fluid dynamics tool used in this study is a Reynolds-averaged Navier–Stokes solver with a transition model (k-ω SST γ-Reθ). The airfoils investigated in this study include NACA airfoils (4, 5, and 6% camber), UltraThin airfoils, and thin cambered plates (3% camber, but various maximum camber locations). Airfoils were examined for lift and drag performance as well as surface pressure and flow… More >

Mohamed Omri^1,*, Yusuf Al-Turki², Ahmed A. Alghamdi¹, Amrid Amnache³, Luc G. Fréchette³

CMC-Computers, Materials & Continua, Vol.71, No.1, pp. 961-977, 2022, DOI:10.32604/cmc.2022.021406

Abstract In this paper, three-dimensional flows in laminar subsonic cascades at relatively low Reynolds numbers (Re < 2500) are presented, based on numerical calculations. The stator and rotor blade designs are those for a MEMS-based Rankine microturbine power-plant-on-a-chip with 109-micron chord blades. Blade passage calculations in 3D were done for different Reynolds numbers, tip clearances (from 0 to 20%) and incidences (0° to 15°) to determine the impact of aerodynamic conditions on the flow patterns. These conditions are applied to a blade passage for a stationary outer casing. The 3D blade passage without tip clearance indicates the presence of two large… More >

S.-C. Hsiao¹, M.S. Ingber²

CMC-Computers, Materials & Continua, Vol.1, No.1, pp. 51-58, 2004, DOI:10.3970/cmc.2004.001.051

Abstract The lateral migration of nonneutrally-buoyant spherical particles in Poiseuille flow is investigated numerically using the boundary element method. In particular, the steady, Navier-Stokes equations are solved using a classical domain integration method treating the nonlinear terms as pseudo-body forces. The numerical results for the lateral migration velocity are compared with experimental data. The numerical results indicate that the lateral migration velocity does not scale linearly with the Reynolds number. The methodology is extended to include non-Newtonian power-law fluids. The migration velocity is significantly affected for particles suspended in this class of fluids and can actually change direction for large values… More >

Zilong Zhang¹, Yajun Yin², Zheng Zhong^1,3, Hongxiao Zhao¹

CMES-Computer Modeling in Engineering & Sciences, Vol.109-110, No.3, pp. 285-302, 2015, DOI:10.3970/cmes.2015.109.285

Abstract Dragonflies possess the highly corrugated wings which distinguish from the ordinary airfoils. To unlock the secrets of the dramatic flight ability of dragonflies, it will be of great significance to investigate the aerodynamic contribution of the corrugations. In this paper, a group of corrugated airfoils were specially designed based on the geometrical characteristics of a typical dragonfly wing. The two-dimensional Navier-Stokes equations were solved using the finite volume method, and the coefficients of lift and drag of the studied airfoils were calculated and compared with those of a flat airfoil and a NACA0008 airfoil. The obtained numerical results illustrated that… More >

D.N. Srinath¹, Sanjay Mittal¹, Veera Manek²

CMES-Computer Modeling in Engineering & Sciences, Vol.51, No.2, pp. 169-190, 2009, DOI:10.3970/cmes.2009.051.169

Abstract A continuous adjoint method is formulated and implemented for the multi-point shape optimization of airfoils at low Re. The airfoil shape is parametrized with a non-uniform rational B-Spline (NURBS). Optimization studies are carried out for two different objective functions. The first involves an inverse function on the lift coefficient over a range of Re. The objective is to determine a shape that results in a lift coefficient of 0.4 at three values of Re: 10, 100 and 500. The second objective involves a direct function on the lift coefficient over a range of angles of attack,a. The lift coefficient is… More >

S. Chantasiriwan¹

CMES-Computer Modeling in Engineering & Sciences, Vol.15, No.3, pp. 137-146, 2006, DOI:10.3970/cmes.2006.015.137

Abstract The multiquadric collocation method is the collocation method based on radial basis function known as multiquadrics. It has been successfully used to solve several linear and nonlinear problems. Although fluid flow problems are among problems previously solved by this method, there is still an outstanding issue regarding the influence of the free parameter of multiquadrics (or the shape parameter) on the performance of the method. This paper provides additional results of using the multiquadric collocation method to solve the lid-driven cavity flow problem. The method is used to solve the problem in the stream function-vorticity formulation and the velocity-vorticity formulation.… More >

Yongsheng Lian ¹

CMES-Computer Modeling in Engineering & Sciences, Vol.72, No.1, pp. 1-16, 2011, DOI:10.3970/cmes.2011.072.001

Abstract In this paper we simulate the unsteady, incompressible, and laminar flow behavior over a flat plate with round leading and trailing edges. A pressure-Poisson method is used to solve the incompressible Navier-Stokes equations. Both convection and diffusion terms are discretized using a second-order accurate central difference method. A second-order accurate split-step scheme with an Adam's predictor corrector time-stepping method is adopted for the time integration. An overlapping moving grid approach is employed to dynamically update the grid due to the plate motion. The effects of the pitch rate, Reynolds number, location of pitch axis, and computational domain size are investigated.… More >

Ori Levin, Wei Shyy¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.4, pp. 523-536, 2001, DOI:10.3970/cmes.2001.002.523

Abstract Typical low Reynolds number airfoils suffer from reduced lift-to-drag ratio and are prone to flow separation. In order to improve the aerodynamic performance of such airfoils in an unsteady freestream, the concept of passive control is investigated. In this study, a membrane with varying thickness distribution and mechanical properties is attached on the upper surface of a modified Clark-Y airfoil and is free to move upwards and downwards in response to the pressure difference across it. The response surface method is employed to investigate the individual and collective effects of the membrane's prestress, elastic modulus, and thickness distribution on aerodynamic… More >

A. Abbassi^1,2, N. Kechiche¹, H. Ben Aissia¹

FDMP-Fluid Dynamics & Materials Processing, Vol.10, No.3, pp. 319-341, 2014, DOI:10.3970/fdmp.2014.010.319

Abstract Jet transition towards a turbulent state is an interesting topic requiring a detailed analysis of the process leading to the onset and amplification of small flow disturbances. Here we examine experimentally the transition process for an isothermal laminar round free jet at low values of the Reynolds number. Close to the inlet nozzle, the turbulence intensity is assumed to be small enough so that the initial shear layer can be considered laminar and the velocity profile uniform. Experimental data are obtained using a Laser Doppler Anemometry (LDA) technique at various longitudinal and transversal coordinates, (x,y). Spectral analysis of the instantaneous… More >