Simulation of dynamic stall using direct-forcing immersed boundary method at low Reynolds number

2018 ◽  
Vol 90 (5) ◽  
pp. 869-876 ◽  
Author(s):  
Nima Vaziri ◽  
Ming-Jyh Chern ◽  
Tzyy-Leng Horng
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Oscillation Amplitude ◽  
Dynamic Stall ◽  
Immersed Boundary ◽  
Ray Casting ◽  
Content Type ◽  
Reduced Frequency ◽  
Direct Forcing ◽  
Low Reynolds

Purpose The purpose of this study is simulation of dynamic stall behavior around the Eppler 387 airfoil in the low Reynolds number flow with a direct-forcing immersed boundary (DFIB) numerical model. Design/methodology/approach A ray-casting method is used to define the airfoil geometry. The governing continuity and Navier–Stokes momentum equations and boundary conditions are solved using the DFIB method. Findings The purposed method is validated against numerical results from alternative schemes and experimental data on static and oscillating airfoil. A base flow regime and different vortices patterns are observed, in accordance with other previously published investigations. Also, the effects of the reduced frequency, the pitch oscillation amplitude and the Reynolds number are studied. The results show that the reduced frequency has a major effect on the flow field and the force coefficients of the airfoil. On the other hand, the Reynolds number of the flow has a little effect on the dynamic stall characteristics of the airfoil at least in the laminar range. Practical implications It is demonstrated that the DFIB model provides an accurate representation of dynamic stall phenomenon. Originality/value The results show that the dynamic stall behavior around the Eppler 387 is different than the general dynamic stall behavior understanding in the shedding phase.

scholarly journals Numerical Simulation of a Pitching Airfoil Under Dynamic Stall of Low Reynolds Number Flow

2019 ◽  
Author(s):  
Mojtaba Honarmand ◽  
Mohammad Hassan Djavareshkian ◽  
Behzad Forouzi Feshalami ◽  
Esmaeil Esmaeilifar
Keyword(s):  
Reynolds Number ◽  
Stokes Equations ◽  
Aerodynamic Force ◽  
Low Reynolds Number ◽  
Oscillation Amplitude ◽  
Dynamic Stall ◽  
Aerodynamic Forces ◽  
Naca0012 Airfoil ◽  
Reduced Frequency ◽  
Low Reynolds

In this research, viscous, unsteady and turbulent fluid flow is simulated numerically around a pitching NACA0012 airfoil in the dynamic stall area. The Navier-Stokes equations are discretized based on the finite volume method and are solved by the PIMPLE algorithm in the open source software, namely OpenFOAM. The SST k - ω model is used as the turbulence model for Low Reynolds Number flows in the order of 105. A homogenous dynamic mesh is used to reduce cell skewness of mesh to prevent non-physical oscillations in aerodynamic forces unlike previous studies. In this paper, the effects of Reynolds number, reduced frequency, oscillation amplitude and airfoil thickness on aerodynamic force coefficients and dynamic stall delay are investigated. These parameters have a significant impact on the maximum lift, drag, the ratio of aerodynamic forces and the location of dynamic stall. The most important parameters that affect the maximum lift to drag coefficient ratio and cause dynamic stall delaying are airfoil thickness and reduced frequency, respectively.

Simulation of dielectric barrier discharge actuator at low Reynolds number

2020 ◽  
Vol 92 (4) ◽  
pp. 571-578
Author(s):  
Nima Vaziri ◽  
Ming-Jyh Chern ◽  
Tzyy-Leng Horng ◽  
Syamsuri Syamsuri
Keyword(s):  
Reynolds Number ◽  
Dielectric Barrier Discharge ◽  
Barrier Discharge ◽  
Low Reynolds Number ◽  
Lift Coefficient ◽  
Immersed Boundary ◽  
Ray Casting ◽  
Dielectric Barrier ◽  
Content Type ◽  
Low Reynolds

Purpose The purpose of this study is to the modeling of the dielectric barrier discharge (DBD) actuator on the Eppler 387 (E387) airfoil in low Reynolds number conditions. Design/methodology/approach A validated direct-forcing immersed boundary method is used to solve the governing equations. A linear electric field model is used to simulate the DBD actuator. A ray-casting technique is used to define the geometry. Findings The purposed model is validated against the former studies. Next, the drag and lift coefficients in the static stall of the E387 airfoil are investigated. Results show that when the DBD actuator is on, both of the coefficients are increased. The effects of the location, applied voltage and applied frequency are also studied and find that the leading-edge actuator with higher voltage and frequency has better improvement in the forces. Finally, the dynamic stall of the E387 with the DBD actuator is considered. The simulation shows that generally when the DBD is on, the lift coefficient in the pitch-up section has lower values and in the pitch-down has higher values than the DBD off mode. Practical implications It is demonstrated that using the DBD actuator on E387 in the low Reynolds number condition can increase the lift and drag forces. Therefore, the application of the airfoil must be considered. Originality/value The results show that sometimes the DBD actuator has different effects on E387 airfoil in low Reynolds number mode than the general understanding of this tool.

Numerical investigations on dynamic stall of low Reynolds number flow around oscillating airfoils

2010 ◽  
Vol 39 (9) ◽  
pp. 1529-1541 ◽  
Author(s):  
Shengyi Wang ◽  
Derek B. Ingham ◽  
Lin Ma ◽  
Mohamed Pourkashanian ◽  
Zhi Tao
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Dynamic Stall ◽  
Numerical Investigations ◽  
Low Reynolds Number Flow ◽  
Reynolds Number Flow ◽  
Number Flow ◽  
Low Reynolds

Turbulence modeling of deep dynamic stall at relatively low Reynolds number

2012 ◽  
Vol 33 ◽  
pp. 191-209 ◽  
Author(s):  
Shengyi Wang ◽  
Derek B. Ingham ◽  
Lin Ma ◽  
Mohamed Pourkashanian ◽  
Zhi Tao
Keyword(s):  
Reynolds Number ◽  
Turbulence Modeling ◽  
Low Reynolds Number ◽  
Dynamic Stall ◽  
Low Reynolds

Shallow and deep dynamic stall for flapping low Reynolds number airfoils

2009 ◽  
Vol 46 (5) ◽  
pp. 883-901 ◽  
Author(s):  
Michael V. Ol ◽  
Luis Bernal ◽  
Chang-Kwon Kang ◽  
Wei Shyy
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Dynamic Stall ◽  
Low Reynolds

Experimental Dynamic Stall study on a low Reynolds number airfoil

2015 ◽  
Author(s):  
Santiago Algozino ◽  
Julio Marañon Di Leo ◽  
Juan Delnero ◽  
Guillermo Capittini
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Dynamic Stall ◽  
Low Reynolds ◽  
Low Reynolds Number Airfoil

A note on the flow coefficients of capillary tube and small orifice restrictors exposed to very low Reynolds number flow

2005 ◽  
Vol 57 (3) ◽  
pp. 116-120 ◽  
Author(s):  
Suat Canbazoğlu ◽  
Fazıl Canbulut
Keyword(s):  
Reynolds Number ◽  
Unsteady Flow ◽  
Capillary Tube ◽  
Low Reynolds Number ◽  
Reynolds Numbers ◽  
Hydraulic Control ◽  
Capillary Tubes ◽  
Content Type ◽  
Control Devices ◽  
Low Reynolds

PurposeThe main objective of this study was to obtain the flow restricting capacity by determining their flow coefficients and to investigate the unsteady flow with low Reynolds number in the flow‐restricting devices such as orifices and capillary tubes having small diameters.Design/methodology/approachThere is an enormous literature on the flow of Newtonian fluids through capillaries and orifices particularly in many application fields of the mechanical and chemical engineering. But most of the experimental results in literature are given for steady flows at moderate and high Reynolds numbers (Re>500). In this study, the unsteady flow at low Reynolds number (10<Re<650) through flow‐restricting devices such as orifices and capillary tubes having very small diameters between 0.35 and 0.70 mm were experimentally investigated.FindingsThe capillary tubes have much more capillarity property with respect to equal diameter orifices. Increasing the ratio of capillary tube length to tube diameter and decreasing the ratio of orifice diameter to pipe diameter before orifice increase the throttling or restricting property of the orifices and the capillary tubes. The orifices can be preferred to the capillary tubes having the same diameter at the same system pressure for the hydraulic systems or circuits requiring small velocity variations. The capillary tubes provide higher pressure losses and they can be also used as hydraulic accumulators in hydraulic control devices to attenuate flow‐induced vibrations because of their large pressure coefficients. An important feature of the results obtained for capillary tubes and small orifices is that as the d/D for orifices increases and the L/d reduces for capillary tubes, higher values C are obtained and the transition from viscous to inertia‐controlled flow appears to take place at lower Reynolds numbers. This may be explained by the fact that for small orifices with high d/D ratios and for capillary tubes with small L/d ratios, the losses due to viscous shear are small. Another important feature of the results is that the least variations in C for small orifices and the higher variations in C for capillary tubes occur when the d/D and L/d ratios are smallest. This has favourable implications in hydraulic control devices since a constant value for the C may be assumed even at relatively low values of Re.Originality/valueTo the authors' knowledge, there is not enough information in the literature about the flow coefficients of unsteady flows through capillary tubes and small orifices at low Reynolds numbers. This paper fulfils this gap.

Numerical Study of Aerodynamic Forces of Two Airfoils in Tandem Configuration at Low Reynolds Number

2021 ◽  
Author(s):  
N. Hosseini ◽  
M. Tadjfar ◽  
A. Abba
Keyword(s):  
Reynolds Number ◽  
Numerical Study ◽  
Low Reynolds Number ◽  
Aerodynamic Forces ◽  
Tandem Configuration ◽  
Pitching Airfoil ◽  
Reduced Frequency ◽  
Low Reynolds ◽  
Lift And Drag ◽  
Two Parameters

Abstract For a tandem airfoil configuration, an airfoil is placed in the wake of an upstream airfoil. This interaction affects the aerodynamic forces of the airfoils, especially the downstream one. In the present study a tandem configuration consists of an upstream pitching airfoil and a downstream stationary airfoil is investigated. This study aims to investigate the role of reduced frequency and pitch amplitude of the upstream airfoil’s motion on lift and drag coefficients of two airfoils. These two parameters play an important role in the formation of vortices. The investigation is done for Selig-Donovan 7003 (SD7003) airfoils at low Reynolds number of 30,000 using a computational fluid dynamics. Incompressible URANS equations were employed for solving the flow field. It was found that for a fixed reduced frequency of 0.5 thrust is produced on the hindfoil for a part of cycle for different pitch amplitudes from light to deep stall while for a fixed pitch amplitude at different reduced frequencies high level of thrust or drag can be produced. The reason is related to the type and intensity of vortex-blade interaction.

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