scholarly journals The aerodynamics of flying snake airfoils in tandem configuration

2021 ◽  
Author(s):  
Farid Jafari ◽  
Daniel Holden ◽  
Roderick LaFoy ◽  
Pavlos P. Vlachos ◽  
John J. Socha
Keyword(s):  
Flow Field ◽  
Field Data ◽  
Strong Dependence ◽  
Separated Flow ◽  
Dorsal Surface ◽  
Ventral Surface ◽  
Aerodynamic Performance ◽  
Cross Sectional ◽  
Tandem Arrangement ◽  
Sectional Shape

Flying snakes flatten their body to form a roughly triangular cross-sectional shape, enabling lift production and horizontal acceleration. While gliding, they also assume an S-shaped posture, which could promote aerodynamic interactions between the fore and the aft body. Such interactions have been studied experimentally; however, very coarse models of the snake's cross-sectional shape were used, and the effects were measured only for the downstream model. In this study, the aerodynamic interactions resulting from the snake's posture were approximated using two-dimensional anatomically accurate airfoils positioned in tandem to mimic the snake's geometry during flight. Load cells were used to measure the lift and drag forces, and flow field data were obtained using digital particle image velocimetry (PIV). The results showed a strong dependence of the aerodynamic performance on the tandem arrangement, with the lift coefficients being generally more influenced than the drag coefficients. Flow field data revealed that the tandem arrangement modified the separated flow and the wake size, and enhanced the lift in cases in which the wake vortices formed closer to the models, producing suction on the dorsal surface. The downforce created by the flow separation from the ventral surface of the models at 0° angle of attack was another significant factor contributing to lift production. A number of cases showing large variations of aerodynamic performance included configurations close to the most probable posture of airborne flying snakes, suggesting that small postural variations could be used to control the glide trajectory.

Research on Sound-Vortex Resonance in Enhancing Performance of an Annular Cascade

2003 ◽  
Author(s):  
Yaxi Qiu ◽  
Jingdong Ge ◽  
Yajun Lu ◽  
Sheng Zhou ◽  
Qiushi Li
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Separated Flow ◽  
Aerodynamic Performance ◽  
Experimental Results ◽  
Acoustic Excitation ◽  
Mechanism Of Interaction ◽  
Shedding Frequency ◽  
Annular Cascade ◽  
Optimal Effect

This paper presents an experimental investigation on the effects of internal acoustic excitation on enhancing performance of an annular cascade. Based on the research on the shedding frequency characteristics of the annular cascade, the mechanism of interaction between the unsteady fluctuation and the separated flow in the annular cascade was systematically investigated by means of unsteady acoustic excitation. The experimental results reveal that the aerodynamic performance of turbomachinery would be improved amazingly if the unsteady interferences in the flow field could be reasonably organized. In experiment, the loss in one cascade passage could be reduced by nearly 30 perents. The optimal effect of the acoustic excitation was studied at different frequencies, intensities and positions of the excitation as well as at different flow incidence angles.

scholarly journals Numerical Study on Wave Induced Flow Field around a Vibrant Monopile Regarding Cross-Sectional Shape

2019 ◽  
Vol 3 (2) ◽  
pp. 1-9 ◽  
Author(s):  
Mohammad Mohammad Beigi Kasvaei ◽  
◽  
Mohammad Hossein Kazeminezhad ◽  
Abbas Yeganeh-Bakhtiary ◽  
◽  
...  
Keyword(s):  
Flow Field ◽  
Numerical Study ◽  
Cross Sectional ◽  
Induced Flow ◽  
Sectional Shape ◽  
Wave Induced

Numerical Simulation of Flow Field Around a Circular-Bladed Butterfly Wind Turbine

2015 ◽  
Author(s):  
Yutaka Hara ◽  
Takahiro Sumi ◽  
Yuhei Matsubara ◽  
Yoshiyuki Yasumoto
Keyword(s):  
Flow Field ◽  
Wind Turbine ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Dynamic Stall ◽  
Speed Ratio ◽  
Half Cycle ◽  
Cross Sectional ◽  
Tip Vortices ◽  
Sectional Shape

Three-dimensional computational fluid dynamics (3D-CFD) was performed to simulate the flow field around an aluminum circular-blade butterfly wind turbine, which is a vertical-axis-type turbine with four circular blades and a diameter of 2.06 m. Under the assumption of a loss factor of 0.8 due to a generator and an AC–DC converter, the CFD results agreed with the experimental results. Although tip vortices were observed at the top and bottom portions of the blades, the vorticity intensity was weaker than that of the straight-blade rotor case. In addition, the cross-sectional shape of the tip vortices seemed to be elliptical for circular blades rather than circular as for straight blades. As the tip speed ratio was less than 2, vortices arising from dynamic stall at maximum-radius portions of blades were observed at the downwind half-cycle as well as the upwind half-cycle. A feature of the vortices shed from a circular blade at the downwind half-cycle was the looped shape.

Scanning electron microscopy of the integument of schistosoma rodhaini

1986 ◽  
Vol 44 ◽  
pp. 132-133
Author(s):  
P. Evers ◽  
C. Schutte ◽  
C. D. Dettman
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Oral Sucker ◽  
Adult Male ◽  
Dorsal Surface ◽  
Ventral Surface ◽  
Sensory Receptors ◽  
East African ◽  
Dorsal Midline ◽  
Scanning Electron

S.rodhaini (Brumpt 1931) is a parasite of East African rodents which may possibly hybridize with the human schistosome S. mansoni. The adult male at maturity measures approximately 3mm long and possesses both oral and ventral suckers and a marked gynaecophoric canal. The oral sucker is surrounded by a ring of sensory receptors with a large number of inwardly-pointing spines set into deep sockets occupying the bulk of the ventral surface of the sucker. Numbers of scattered sensory receptors are found on both dorsal and ventral surfaces of the head (Fig. 1) together with two conspicuous rows of receptors situated symmetrically on each side of the midline. One row extends along the dorsal surface of the head midway between the dorsal midline and the lateral margin.

On the cross-sectional shape of the cellulose crystallites in the tunicate Halocynthia papillosa

1990 ◽  
Vol 48 (3) ◽  
pp. 566-567
Author(s):  
J.-F. Revol ◽  
Y. Van Daele ◽  
F. Gaill
Keyword(s):  
Contrast Imaging ◽  
Animal Kingdom ◽  
Bright Field ◽  
Field Mode ◽  
Cross Sectional ◽  
Ultrathin Sections ◽  
The Cross ◽  
Sectional Shape ◽  
Valonia Ventricosa ◽  
C Nmr

The only form of cellulose which could unequivocally be ascribed to the animal kingdom is the tunicin that occurs in the tests of the tunicates. Recently, high-resolution solid-state l3C NMR revealed that tunicin belongs to the Iβ form of cellulose as opposed to the Iα form found in Valonia and bacterial celluloses. The high perfection of the tunicin crystallites led us to study its crosssectional shape and to compare it with the shape of those in Valonia ventricosa (V.v.), the goal being to relate the cross-section of cellulose crystallites with the two allomorphs Iα and Iβ.In the present work the source of tunicin was the test of the ascidian Halocvnthia papillosa (H.p.). Diffraction contrast imaging in the bright field mode was applied on ultrathin sections of the V.v. cell wall and H.p. test with cellulose crystallites perpendicular to the plane of the sections. The electron microscope, a Philips 400T, was operated at 120 kV in a low intensity beam condition.

Automated 3D measurement of fiber cross section morphology in handsheets

2012 ◽  
Vol 27 (2) ◽  
pp. 264-269 ◽  
Author(s):  
Christian Lorbach ◽  
Ulrich Hirn ◽  
Johannes Kritzinger ◽  
Wolfgang Bauer
Keyword(s):  
Image Analysis ◽  
Cross Section ◽  
Cross Sections ◽  
Image Plane ◽  
3D Measurement ◽  
Cross Sectional ◽  
Fiber Cross Section ◽  
Fiber Wall ◽  
Sectional Shape ◽  
Cross Section Geometry

Abstract We present a method for 3D measurement of fiber cross sectional morphology from handsheets. An automated procedure is used to acquire 3D datasets of fiber cross sectional images using an automated microtome and light microscopy. The fiber cross section geometry is extracted using digital image analysis. Simple sample preparation and highly automated image acquisition and image analysis are providing an efficient tool to analyze large samples. It is demonstrated that if fibers are tilted towards the image plane the images of fiber cross sections are always larger than the true fiber cross section geometry. In our analysis the tilting angles of the fibers to the image plane are measured. The resulting fiber cross sectional images are distorted to compensate the error due to fiber tilt, restoring the true fiber cross sectional shape. We use an approximated correction, the paper provides error estimates of the approximation. Measurement results for fiber wall thickness, fiber coarseness and fiber collapse are presented for one hardwood and one softwood pulp.

Study of Correctly Expanded Sonic Jet with Air Tabs

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Arun Prasad R ◽  
Thanigaiarasu S ◽  
Sembaruthi M ◽  
Rathakrishnan E
Keyword(s):  
Numerical Study ◽  
Cross Sectional ◽  
Potential Core ◽  
Convergent Nozzle ◽  
Jet Mixing ◽  
Pressure Profiles ◽  
Constant Diameter ◽  
Sonic Jet ◽  
Sectional Shape ◽  
Length Reduction

AbstractThe present numerical study is to understand the effect of air tabs located at the exit of a convergent nozzle on the spreading and mixing characteristics of correctly expanded sonic primary jet. Air tabs used in this study are two secondary jets issuing from constant diameter tubes located diametrically opposite at the periphery of the primary nozzle exit, normal to the primary jet. Two air tabs of Mach numbers 1.0 to 1.4, in steps of 0.1 are considered in this study. The mixing modification caused by air tabs are analysed by considering the mixing of uncontrolled (free) primary jet as a reference. Substantial enhancement in jet mixing is achieved with Mach 1.4 air tabs, which results in 80 % potential core length reduction. The total pressure profiles taken on the plane (YZ) normal to the primary jet axis, at various locations along the primary jet centreline revealed the modification of the jet cross sectional shape by air tabs. The stream-wise vortices and bifurcation of the primary jet caused by air tabs are found to be the mechanism behind the enhanced jet mixing.

Experimental investigation and optimization on field shaper structure parameters in magnetic pulse welding

2021 ◽  
pp. 095440542110148
Author(s):  
Yingzi Chen ◽  
Zhiyuan Yang ◽  
Wenxiong Peng ◽  
Huaiqing Zhang
Keyword(s):  
Magnetic Field ◽  
High Speed ◽  
Light Metal ◽  
Magnetic Pulse ◽  
Cross Sectional ◽  
Magnetic Pulse Welding ◽  
Pulse Welding ◽  
Sectional Shape ◽  
Welding System ◽  
The Magnetic Field

Magnetic pulse welding is a high-speed welding technology, which is suitable for welding light metal materials. In the magnetic pulse welding system, the field shaper can increase the service life of the coil and contribute to concentrating the magnetic field in the welding area. Therefore, optimizing the structure of the field shaper can effectively improve the efficiency of the system. This paper analyzed the influence of cross-sectional shape and inner angle of the field shaper on the ability of concentrating magnetic field via COMSOL software. The structural strength of various field shapers was also analyzed in ABAQUS. Simulation results show that the inner edge of the field shaper directly affects the deformation and welding effect of the tube. So, a new shape of field shaper was proposed and the experimental results prove that the new field shaper has better performance than the conventional field shaper.

Blast Wave Shaping by Altering Cross‐Sectional Shape

2021 ◽  
Author(s):  
Kelly Williams ◽  
Martin J. Langenderfer ◽  
Gayla Olbricht ◽  
Catherine E. Johnson
Keyword(s):  
Blast Wave ◽  
Cross Sectional ◽  
Sectional Shape
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