Experimental study on the effect of bionic flap parameters on airfoil aerodynamic performance

2021 ◽  
pp. 095440622110001
Author(s):  
Lishu Hao ◽  
Yongwei Gao ◽  
Yunbin Shang
Keyword(s):  
Lift Coefficient ◽  
Separated Flow ◽  
Control Mechanisms ◽  
Flow Conditions ◽  
Theoretical Support ◽  
Attached Flow ◽  
Aeronautical Engineering ◽  
Edge Separation ◽  
Lift Line ◽  
Insight Into

The effects of bionic flap on airfoil performance were experimentally studied to provide theoretical support for the application of the bionic flap in aeronautical engineering. Seven kinds of bionic flaps were used to study the effects of the key flap parameters, including the flap angle, length, shape, and position, at a Reynolds number of Re = 0.8 × 106. At small angle of attacks (AoAs), the drag and pitching moment increased and the lift reduced when using the bionic flap. While at high AoAs, the lift increased and the drag reduced, which improved the airfoil stall characteristics. The configuration of deflection bionic flap had the smallest initial AoA for improving the airfoil stall characteristics in the seven kinds of bionic flaps. More than eight degrees of the effective AoA range for improving lift characteristics could be achieved. The maximum lift coefficient could be increased by 3.9%. Additionally, the control mechanisms of the flap under different flow conditions (attached flow and separated flow) were deeply studied. In the attached flow, the effective camber and thickness of the basic airfoil could be changed by the flap, resulting that the flow around the airfoil was affected, which in turn affected the Cl and the slope of the lift line. In the separated flow, the flap affected the flow around the airfoil by controlling the development of the trailing edge separation vortex. These research results confirmed the aerodynamic mechanisms for the formation of double layered feathers when birds land, and provided insight into application of bionic flaps in aeronautical engineering.

A theoretical investigation of enhanced lift in the presence of thin aerofoil stall

1999 ◽  
Vol 103 (1023) ◽  
pp. 237-244 ◽  
Author(s):  
W. W. H. Yeung ◽  
G. V. Parkinson
Keyword(s):  
Flat Plate ◽  
Flow Model ◽  
Separated Flow ◽  
Leading Edge ◽  
Geometrical Parameters ◽  
Separation Flow ◽  
Attached Flow ◽  
Positive Angle ◽  
Edge Separation ◽  
Potential Flow Model

Abstract A theoretical study is presented for the investigation of a potential-flow model for enhancing lift over a flat-plate aerofoil experiencing thin aerofoil stall. Rather than suppressing the leading-edge separation, flow is assumed to separate tangentially at the leading edge and made to reattach smoothly at the tip of a forward-facing fence joining the plate tangentially on its upper surface to avoid any unnecessary stagnated flow. The length of the fence and its location from the leading edge form two geometrical parameters. At any positive angle of attack, the resulting bounding streamline emanating from the leading edge and terminating at the tip of the fence is simulated by using suitable mathematical singularities subject to boundary conditions such as attaining a finite velocity at each critical point of the conformal mapping involved, and the condition of finite pressure gradient at reattachment, when applicable. Computational results from varying these two geometrical parameters indicate that the lift from each model is enhanced, as compared with the attached flow model around a simple flat plate and the original separated flow model by Kirchhoff.

Calculation of Attached or Partially Separated Flow Around Airfoil Sections

1977 ◽  
Vol 21 (02) ◽  
pp. 69-81
Author(s):  
Jerome H. Milgram
Keyword(s):  
Separated Flow ◽  
Leading Edge ◽  
Perturbation Series ◽  
Unified Theory ◽  
Physical Plane ◽  
Trailing Edge ◽  
Separation Flows ◽  
Attached Flow ◽  
Approach Zero ◽  
Edge Separation

Two-dimensional airfoil theory is developed for incompressible flow, for which most aspects of the solution are found in a "mapped plane." Although the airfoil contour has large slopes in the physical plane when the airfoil has a round leading edge, the slopes in the mapped plane are small and uniformly approach zero as the airfoil thickness and camber ratios are made to approach zero by an affine transformation on the airfoil shape. Because of the small slopes in the mapped plane, a perturbation series is appropriate there. A relatively unified theory is given for attached and partially separated (trailing-edge separation) flows. The results of calculations by this theory are compared with the results of other theories and with measurements. The attached-flow theory is shown to be especially appropriate for thin marine propeller sections with blunted leading edges. Some new data on the pressure distribution across the wake at the trailing edge of an airfoil in partially separated flow are presented.

scholarly journals Selective packaging of mitochondrial proteins into extracellular vesicles prevents the release of mitochondrial DAMPs

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kiran Todkar ◽  
Lilia Chikhi ◽  
Véronique Desjardins ◽  
Firas El-Mortada ◽  
Geneviève Pépin ◽  
...  
Keyword(s):  
Extracellular Vesicles ◽  
Mitochondrial Proteins ◽  
Control Mechanisms ◽  
Mitochondrial Content ◽  
Sorting Nexin ◽  
Inflammatory Conditions ◽  
Selective Targeting ◽  
Molecular Patterns ◽  
Damage Associated Molecular Patterns ◽  
Insight Into

AbstractMost cells constitutively secrete mitochondrial DNA and proteins in extracellular vesicles (EVs). While EVs are small vesicles that transfer material between cells, Mitochondria-Derived Vesicles (MDVs) carry material specifically between mitochondria and other organelles. Mitochondrial content can enhance inflammation under pro-inflammatory conditions, though its role in the absence of inflammation remains elusive. Here, we demonstrate that cells actively prevent the packaging of pro-inflammatory, oxidized mitochondrial proteins that would act as damage-associated molecular patterns (DAMPs) into EVs. Importantly, we find that the distinction between material to be included into EVs and damaged mitochondrial content to be excluded is dependent on selective targeting to one of two distinct MDV pathways. We show that Optic Atrophy 1 (OPA1) and sorting nexin 9 (Snx9)-dependent MDVs are required to target mitochondrial proteins to EVs, while the Parkinson’s disease-related protein Parkin blocks this process by directing damaged mitochondrial content to lysosomes. Our results provide insight into the interplay between mitochondrial quality control mechanisms and mitochondria-driven immune responses.

Three-Dimensional and Rotational Aerodynamics on the NREL Phase VI Wind Turbine Blade

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Alvaro Gonzalez ◽  
Xabier Munduate
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Three Dimensional ◽  
Separated Flow ◽  
Leading Edge ◽  
Wind Turbine Blade ◽  
Trailing Edge ◽  
Rotating Blade ◽  
Nrel Phase Vi ◽  
Edge Separation

This work undertakes an aerodynamic analysis over the parked and the rotating NREL Phase VI wind turbine blade. The experimental sequences from NASA Ames wind tunnel selected for this study respond to the parked blade and the rotating configuration, both for the upwind, two-bladed wind turbine operating at nonyawed conditions. The objective is to bring some light into the nature of the flow field and especially the type of stall behavior observed when 2D aerofoil steady measurements are compared to the parked blade and the latter to the rotating one. From averaged pressure coefficients together with their standard deviation values, trailing and leading edge separated flow regions have been found, with the limitations of the repeatability of the flow encountered on the blade. Results for the parked blade show the progressive delay from tip to root of the trailing edge separation process, with respect to the 2D profile, and also reveal a local region of leading edge separated flow or bubble at the inner, 30% and 47% of the blade. For the rotating blade, results at inboard 30% and 47% stations show a dramatic suppression of the trailing edge separation, and the development of a leading edge separation structure connected with the extra lift.

Performance Enhancement Analysis of a Horizontal Axis Wind Turbine by Vortex Trapping Cavity

2021 ◽  
pp. 1-13
Author(s):  
Khaoula Qaissi ◽  
Omer A Elsayed ◽  
Mustapha Faqir ◽  
Elhachmi Essadiqi
Keyword(s):  
Wind Turbine ◽  
Performance Enhancement ◽  
Lift Coefficient ◽  
Separated Flow ◽  
National Renewable Energy Laboratory ◽  
Wake Region ◽  
High Twist ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds ◽  
Nrel Phase Vi

Abstract A wind turbine blade has the particularity of containing twisted and tapered thick airfoils. The challenge with this configuration is the highly separated flow in the region of high twist. This research presents a numerical investigation of the effectiveness of a Vortex Trapping Cavity (VTC) on the aerodynamics of the National renewable Energy laboratory (NREL) Phase VI wind turbine. First, simulations are conducted on the S809 profile to study the fluid flow compared to the airfoil with the redesigned VTC. Secondly, the blade is simulated with and without VTC to assess its effect on the torque and the flow patterns. The results show that for high angles of incidence at Rec=106, the lift coefficient increases by 10% and the wake region appears smaller for the case with VTC. For wind speeds larger than 10 m/s, the VTC improves the torque by 3.9%. This is due to the separation that takes place in the vicinity of the VTC and leads to trapping early separation eddies inside the cell. These eddies roll up forming a coherent laminar vortex structure, which in turn sheds periodically out of the cell. This phenomenon favourably reshapes excessive flow separation, reenergizes the boundary layer and globally improves blade torque.

Transition Mechanisms in Laminar Separated Flow Under Simulated Low Pressure Turbine Aerofoil Conditions

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Jerrit Dähnert ◽  
Christoph Lyko ◽  
Dieter Peitsch
Keyword(s):  
Reynolds Number ◽  
Separation Bubble ◽  
Separated Flow ◽  
Low Pressure ◽  
Main Flow ◽  
Test Facility ◽  
Flow Conditions ◽  
Laminar Separation ◽  
Free Stream Turbulence ◽  
Low Pressure Turbine

Based on detailed experimental work conducted at a low speed test facility, this paper describes the transition process in the presence of a separation bubble with low Reynolds number, low free-stream turbulence, and steady main flow conditions. A pressure distribution has been created on a long flat plate by means of a contoured wall opposite of the plate, matching the suction side of a modern low-pressure turbine aerofoil. The main flow conditions for four Reynolds numbers, based on suction surface length and nominal exit velocity, were varied from 80,000 to 300,000, which covers the typical range of flight conditions. Velocity profiles and the overall flow field were acquired in the boundary layer at several streamwise locations using hot-wire anemometry. The data given is in the form of contours for velocity, turbulence intensity, and turbulent intermittency. The results highlight the effects of Reynolds number, the mechanisms of separation, transition, and reattachment, which feature laminar separation-long bubble and laminar separation-short bubble modes. For each Reynolds number, the onset of transition, the transition length, and the general characteristics of separated flow are determined. These findings are compared to the measurement results found in the literature. Furthermore, the experimental data is compared with two categories of correlation functions also given in the literature: (1) correlations predicting the onset of transition and (2) correlations predicting the mode of separated flow transition. Moreover, it is shown that the type of instability involved corresponds to the inviscid Kelvin-Helmholtz instability mode at a dominant frequency that is in agreement with the typical ranges occurring in published studies of separated and free-shear layers.

An Investigation of Flow Fields Over Multi-Element Aerofoils

2001 ◽  
Vol 124 (1) ◽  
pp. 154-165 ◽  
Author(s):  
S. R. Maddah ◽  
H. H. Bruun
Keyword(s):  
Flow Field ◽  
Computational Study ◽  
Separated Flow ◽  
Mean Flow ◽  
Model Configuration ◽  
Attached Flow ◽  
The Mean ◽  
Flap Deflection ◽  
Comparative Results ◽  
Lift And Drag

This paper presents results obtained from a combined experimental and computational study of the flow field over a multi-element aerofoil with and without an advanced slat. Detailed measurements of the mean flow and turbulent quantities over a multi-element aerofoil model in a wind tunnel have been carried out using stationary and flying hot-wire (FHW) probes. The model configuration which spans the test section 600mm×600mm, is made of three parts: 1) an advanced (heel-less) slat, 2) a NACA 4412 main aerofoil and 3) a NACA 4415 flap. The chord lengths of the elements were 38, 250 and 83 mm, respectively. The results were obtained at a chord Reynolds number of 3×105 and a free Mach number of less than 0.1. The variations in the flow field are explained with reference to three distinct flow field regimes: attached flow, intermittent separated flow, and separated flow. Initial comparative results are presented for the single main aerofoil and the main aerofoil with a nondeflected flap at angles of attacks of 5, 10, and 15 deg. This is followed by the results for the three-element aerofoil with emphasis on the slat performance at angles of attack α=10, 15, 20, and 25 deg. Results are discussed both for a nondeflected flap δf=0deg and a deflected flap δf=25deg. The measurements presented are combined with other related aerofoil measurements to explain the main interaction of the slat/main aerofoil and main aerofoil/flap both for nondeflected and deflected flap conditions. These results are linked to numerically calculated variations in lift and drag coefficients with angle of attack and flap deflection angle.

Sparse identification of nonlinear unsteady aerodynamics of the oscillating airfoil

2020 ◽  
pp. 095441002095987
Author(s):  
Chong Sun ◽  
Tian Tian ◽  
Xiaocheng Zhu ◽  
Zhaohui Du
Keyword(s):  
Flow Model ◽  
Dynamic Change ◽  
Unsteady Aerodynamics ◽  
Separated Flow ◽  
General System ◽  
Training Data ◽  
Loop Control ◽  
First Order ◽  
Attached Flow ◽  
Unsteady Lift

Reduced-order models are widely used in aerospace engineering. A model for unsteady aerodynamics is desirable for designing the blades of wind turbines. Recently, sparse identification of nonlinear dynamics with control was introduced to identify the parameters of an input-output dynamical system. In this paper, two models for attached flows and one for separated flows are identified through this technique. For the unsteady lift of the attached flow, Model I is a linear model that presents the dynamic change of an unsteady lift to a static lift. Model II was built based on Model I in order to obtain a more general system with closed-loop control. It has a first-order inert element that delays the overall input of the static lift. The Model II results replicate the training data very well and give an accurate prediction of other oscillating cases with different oscillation amplitudes, reduced frequency or mean angle of attack. For the unsteady lift of the separated flow, Model III is identified as a nonlinear model, which also has a first-order inert element. This model captures the nonlinear aerodynamics of the separated flow and replicates the training cases well. In addition, the prediction of Model III has good agreement with the numerical results.

scholarly journals Biofilm formation by group A Streptococcus: a role for the streptococcal regulator of virulence (Srv) and streptococcal cysteine protease (SpeB)

Microbiology ◽  
2009 ◽  
Vol 155 (1) ◽  
pp. 46-52 ◽  
Author(s):  
Christopher D. Doern ◽  
Amity L. Roberts ◽  
Wenzhou Hong ◽  
Jessica Nelson ◽  
Slawomir Lukomski ◽  
...  
Keyword(s):  
Cysteine Protease ◽  
Biofilm Formation ◽  
Group A Streptococcus ◽  
Immunoblot Analysis ◽  
Wild Type ◽  
Flow Conditions ◽  
Group A ◽  
Streptococcus A ◽  
Insight Into ◽  
Western Immunoblot Analysis

Recently, biofilms have become a topic of interest in the study of the human pathogen group A Streptococcus (GAS). In this study, we sought to learn more about the make-up of these structures and gain insight into biofilm regulation. Enzymic studies indicated that biofilm formation by GAS strain MGAS5005 required an extracellular protein and DNA component(s). Previous results indicated that inactivation of the transcriptional regulator Srv in MGAS5005 resulted in a significant decrease in virulence. Here, inactivation of Srv also resulted in a significant decrease in biofilm formation under both static and flow conditions. Given that production of the extracellular cysteine protease SpeB is increased in the srv mutant, we tested the hypothesis that increased levels of active SpeB may be responsible for the reduction in biofilm formation. Western immunoblot analysis indicated that SpeB was absent from MGAS5005 biofilms. Complementation of MGAS5005Δsrv restored the biofilm phenotype and eliminated the overproduction of active SpeB. Inhibition of SpeB with E64 also restored the MGAS5005Δsrv biofilm to wild-type levels.

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