Unsteady Numerical Analysis of Flow Across 2D Cylinder

2010 ◽  
Author(s):  
Yaling Peng ◽  
Zhiguo Zhang ◽  
Fangliang Wu ◽  
Dakui Feng
Keyword(s):  
Strouhal Number ◽  
Excellent Agreement ◽  
Incidence Angle ◽  
Flow Direction ◽  
Incident Angle ◽  
Numerical Results ◽  
Published Data ◽  
Angle Of Incidence ◽  
Square Cylinder ◽  
Navier Stokes Equation

2-D computational analyses were conducted for unsteady viscous flow across cylinders of different geometries and different incident angle. Circular, square and elliptic (both at 0° and 90° angles of incidence) cylinders were examined. The calculations were performed by solving the unsteady 2-D Navier-Stokes equation at Re = 100. The calculated results produce drag and lift coefficients, as well as Strouhal number in excellent agreement with published data. Calculations for unsteady, incompressible 2D flow around a square cylinder at incidence angle of 0° and 45° and for Reynolds number = 100 were carried out. Cycle independence and grid independence results were obtained for the Strouhal number. The results were in excellent agreement with the available experimental and numerical results. Numerical results show that the Strouhal number increases with fluid angle of incidence on the cylinder. The wake behind the cylinder is wider and more violent for a square cylinder at 45° incidence compared to a square at 0° this is due to the increase in the characteristic length in the flow direction. The Strouhal number is highest for elliptic geometry among all cylinders in this research. For the geometries elliptic at 0° at Re = 100, there is not vortex shedding behind the cylinder. This is due to dominance of inertia forces over viscous forces. The present study was carried out for a 2-D single cylinder at fixed location inside a channel for unidirectional velocity. To get more accurate results computation on 3-D geometry should be carried out.

Investigation of the Flow and Heat Transfer around Cylinders at Low Re

2010 ◽  
Vol 156-157 ◽  
pp. 1630-1634
Author(s):  
Lei Yue ◽  
Zhi Guo Zhang ◽  
Da Kui Feng ◽  
Ashvinikumar V. Mudaliar
Keyword(s):  
Heat Transfer ◽  
Strouhal Number ◽  
Excellent Agreement ◽  
Stokes Equations ◽  
Flow Direction ◽  
Incident Angle ◽  
Numerical Results ◽  
Published Data ◽  
Square Cylinder ◽  
Flow And Heat Transfer

2-D computational analyses were conducted for unsteady viscous flow and heat transfer across cylinders of different geometries and different incident angle. Circular, square (both at 0° and 90° angles of incidence) and elliptic cylinders were examined. The calculations were performed by solving the unsteady 2-D Navier-Stokes equations at Re = 100. The calculated results produce drag and lift coefficients, as well as Strouhal number in excellent agreement with published data. Calculations for unsteady, incompressible 2-D flow around a square cylinder at incidence angle of 0° and 45° and for Reynolds number = 100 were carried out. Cycle independence and grid independence results were obtained for the Strouhal number. The results were in excellent agreement with the available experimental and numerical results. Numerical results show that the Strouhal number increases with fluid angle of incidence on the cylinder. The wake behind the cylinder is wider and more violent for a square cylinder at 45° incidence compared to a square at 0° this is due to the increase in the characteristic length in the flow direction. The present studywas carried out for a 2-D single cylinder at fixed location inside a channel for unidirectional velocity. To get more accurate results computation on 3-D geometry should be carried out.

scholarly journals The asymptotic iteration method for the angular spheroidal eigenvalues with arbitrary complex size parameter c

2006 ◽  
Vol 84 (2) ◽  
pp. 121-129 ◽  
Author(s):  
T Barakat ◽  
K Abodayeh ◽  
B Abdallah ◽  
O M Al-Dossary
Keyword(s):  
Excellent Agreement ◽  
Iteration Method ◽  
Full Range ◽  
Numerical Results ◽  
Asymptotic Iteration Method ◽  
Published Data ◽  
Size Parameter ◽  
Arbitrary Complex ◽  
Parameter Values

The asymptotic iteration method is applied to calculate the angular spheroidal eigenvalues [Formula: see text] (c) with arbitrary complex size parameter c. It is shown that the numerical results obtained for [Formula: see text] (c) are all in excellent agreement with the available published data over the full range of parameter values [Formula: see text] m, and c. Some representative values of [Formula: see text] (c) for large real c are also given.PACS No.: 02.70.–c.

Wake Formation for an Oscillating Small-Incidence-Angle Cylinder Pair in Cross-Flow

2011 ◽  
Author(s):  
Mir M. Hayder
Keyword(s):  
Incidence Angle ◽  
Flow Direction ◽  
Incident Angle ◽  
Cross Flow ◽  
Wake Flow ◽  
Circular Cylinders ◽  
Mean Flow ◽  
Small Incidence ◽  
The Mean ◽  
Wake Formation

The wake region of a pair of equal-diameter staggered circular cylinders in cross-flow is investigated experimentally for Reynolds numbers, based on the mean flow velocity, U, and the cylinder diameter, D, within the range 540 ≤ Re ≤ 755. The centre-to-centre pitch ratio and stagger angle of the cylinders at their mean position are P/D = 2.0 and α = 16°, respectively. In an earlier study, wake formation of a small-incident-angle cylinder pair was investigated for forced oscillation (transverse to the flow direction) of the upstream cylinder only. The present study is aimed to reveal the modification of the wake when the oscillation is shifted from the upstream to downstream cylinder or vice versa. Results with cylinder excitation frequencies in the range 0.07 ≤ feD/U ≤ 1.10 are reported. It is observed that for both upstream and downstream cylinder oscillations with frequency feD/U ≤ 0.10 the wake flow patterns remain essentially the same as those of the corresponding static cases. However, for frequency feD/U > 0.10 the wake undergoes considerable modification vis-a`-vis when the cylinders are stationary, and the flow pattern within the wake is strongly dependent on feD/U value. As also observed in the previous study, there are distinct regions of synchronization between the dominant wake periodicities and the cylinder oscillation over the whole range of feD/U. These synchronizations involve sub- and super-harmonics as well as fundamental synchronizations and are the result of the formation of two rows of vortices, one on either side of the combined wake of the cylinder pair. The manner in which the wake responds to the cylinder oscillation depends strongly on whether it is the upstream or downstream cylinder which is oscillating. Flow-visualization images suggests that the synchronizations on the mean-flow side of the downstream cylinder occur from the outer vortices shed by the downstream cylinder, and those on the mean-flow side of the upstream cylinder occur from the vortices formed by the interaction of the two gap shear layers and the outer shear layer separated from the upstream cylinder.

Flow-Induced Vibrations of a Square Cylinder With Combined Translational and Rotational Oscillations

2016 ◽  
Author(s):  
T. P. Miyanawala ◽  
Mengzhao Guan ◽  
Rajeev K. Jaiman
Keyword(s):  
Incidence Angle ◽  
Translational Motion ◽  
Published Data ◽  
Square Cylinder ◽  
Flow Induced Vibration ◽  
Flow Induced Vibrations ◽  
3D Effects ◽  
Motion Parameters ◽  
Lock In ◽  
Rotational Oscillations

In this work, we investigate the combined translation and rotational flow-induced vibration (FIV) of elastically mounted square cylinder in a free-stream at zero incidence angle. We employ a partitioned iterative scheme to solve coupled fluid-rigid body interaction using unstructured grid. The fluid-solid coupled solver and the mesh is verified by investigating pure translational motion cases at zero incidence against published data for a laminar flow past a square cylinder. Further analysis revealed that the increase of mass ratio shifts the lock-in to higher reduced velocity region. The influence of of the torsional motion parameters is analyzed for a pure rotational case. The combined 3-DOF motion is next considered while keeping the above two analyses as reference. It was evident that, even small yaw vibrations adds circulation to the flow and thus increases the vortex intensity. This phenomenon is identified to be responsible for the differences of motion parameters between the isolated DOF cases and combined 3DOF cases. Finally, for the completeness of the study, the influence of 3D effects is estimated for the same geometry and also a high Re case is presented.

scholarly journals Polarization-Sensitive and Wide Incidence Angle-Insensitive Fabry–Perot Optical Cavity Bounded by Two Metal Grating Layers

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5382
Author(s):  
Jehwan Hwang ◽  
Zahyun Ku ◽  
Jiyeon Jeon ◽  
Yeongho Kim ◽  
Deok-Kee Kim ◽  
...  
Keyword(s):  
Incidence Angle ◽  
Incident Angle ◽  
Incident Light ◽  
Extinction Ratio ◽  
Cavity Resonance ◽  
Angle Of Incidence ◽  
Metal Grating ◽  
Imaging Array ◽  
Fabry Perot ◽  
Polarimetric Imaging

Infrared (IR) polarimetric imaging has attracted attention as a promising technology in many fields. Generally, superpixels consisting of linear polarizer elements at different angles plus IR imaging array are used to obtain the polarized target signature by using the detected polarization-sensitive intensities. However, the spatial arrangement of superpixels across the imaging array may lead to an incorrect polarimetric signature of a target, due to the range of angles from which the incident radiation can be collected by the detector. In this article, we demonstrate the effect of the incident angle on the polarization performance of an alternative structure where a dielectric layer is inserted between the nanoimprinted subwavelength grating layers. The well-designed spacer creates the Fabry–Perot cavity resonance, and thereby, the intensity of transverse-magnetic I-polarized light transmitted through two metal grating layers is increased as compared with a single-layer metal grating, whereas transverse-electric (TE)-transmitted light intensity is decreased. TM-transmittance and polarization extinction ratio (PER) of normally incident light of wavelength 4.5 μm are obtained with 0.49 and 132, respectively, as the performance of the stacked subwavelength gratings. The relative change of the PERs for nanoimprint-lithographically fabricated double-layer grating samples that are less than 6% at an angle of incidence up to 25°, as compared to the normal incidence. Our work can pave the way for practical and efficient polarization-sensitive elements, which are useful for many IR polarimetric imaging applications.

Numerical study of the rounded corners effect on flow past a square cylinder

2015 ◽  
Vol 25 (4) ◽  
pp. 686-702 ◽  
Author(s):  
Sajjad Miran ◽  
Chang Hyun Sohn
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Strouhal Number ◽  
Lift Coefficient ◽  
Numerical Results ◽  
The Body ◽  
Square Cylinder ◽  
Content Type ◽  
Flow Past ◽  
Corner Radius

Purpose – The purpose of this paper is to numerically investigate the influence of corner radius on flow past a square cylinder at a Reynolds number 500. Design/methodology/approach – Six models were studied, for R/D=0 (square cylinder), 0.1, 0.2, 0.3, 0.4, and 0.5 (circular cylinder), where R is the corner radius and D is the characteristic dimension of the body. The transient two-dimensional (2D) laminar and large eddy simulations (LES) models were employed using finite volume code. The Strouhal number, mean drag coefficient (CD), and root mean square (RMS) value of lift coefficient (CL,RMS), for different R/D values, were computed and compared with experimental and other numerical results. Findings – The computational results showed good agreement with previously published results for a Reynolds number, Re=500. It was found that the corner effect on a square cylinder greatly influences the flow characteristics around the cylinder. Results indicate that, as the corner radius ratio, R/D, increases, the Strouhal number increases rapidly for R/D=0-0.2, and then gradually rises between R/D=0.2 and 0.5. The minimum values of the mean drag coefficient and the RMS value of lift coefficient were found around R/D=0.2, which is verified by the time averaged streamwise velocity deficit profile. Originality/value – On the basis of the numerical results, it is concluded that rounded corners on a square cylinder are useful in reducing the drag and lift forces generated behind a cylinder. Finally, it is suggested that with a rounded corner ratio of around R/D=0.2, the drag and oscillation of the cylinder can be greatly reduced, as compared to circular and square cylinders.

Numerical and Experimental Studies of Liquid Sloshing in Rectangular Tanks Using a Particle Method

2008 ◽  
Author(s):  
M. M. Gao ◽  
C. G. Koh ◽  
C. Luo
Keyword(s):  
Experimental Studies ◽  
Three Dimensional ◽  
Particle Method ◽  
Wave Theory ◽  
Particle Number Density ◽  
Numerical Results ◽  
Published Data ◽  
Navier Stokes Equation ◽  
Shake Table Tests ◽  
Inclined Angle

The sloshing waves in rectangular tanks are studied experimentally and numerically based on the fully nonlinear wave theory. A moving-particle semi-implicit (MPS) method belonging to the category of the particle method is utilized to solve the Navier-Stokes equation that is the governing equation of the incompressible fluids. The motion of each particle is calculated through interactions with neighboring particles covered with the kernel function. The governing equations are solved by Lagrangian approach and no grid is needed in the computation. The incompressibility is satisfied by keeping the particle number density constant. When the tank undergoes two-dimensional motion, the numerical results obtained are found to be in good agreement with other published data as well as our experimental results obtained by shake-table tests. Experiments with rectangular tanks have been conducted to validate the numerical results, for which favorable agreement is shown. Results will also be presented for the study which is currently extended to three dimensional sloshing by exciting the tank at an inclined angle.

scholarly journals A Convenient Way to Determine the Optimum Angle of Incidence of Fizeau Interferometer

2021 ◽  
Vol 11 (22) ◽  
pp. 10678
Author(s):  
Bowen Du ◽  
Yuquan Zheng ◽  
Chao Lin ◽  
Hang Zhang
Keyword(s):  
Incidence Angle ◽  
Incident Angle ◽  
Wedge Angle ◽  
Normal Incidence ◽  
Angle Of Incidence ◽  
Fizeau Interferometer ◽  
Optimal Angle ◽  
Suppression Effect ◽  
Estimation Formula ◽  
Modified Method

In a Fizeau interferometer, off-axis illumination will lead to fringe optimization. Primarily due to the unique structure of our interferometer, we first analyze the influence of the optical properties of the parallel plate as a part of the interferometer on the optimal incident angle. Generally, the incident angle determination is mainly based on the graphing method proposed by Langenbeck and the estimation formula proposed by Kajava. However, Langenbeck’s method is cumbersome, and the error of Kajava’s estimation formula is large. Based on the predecessors, this paper proposes a modified method of determining the optimal angle of incidence and further derives more accurate optimal angle expressions than Kajava’s. By simply substituting the wedge angle of the wedge cavity and the reflectivity of the cavity, the optimum incidence angle can be obtained immediately. Thus, it eliminates the tedious and complex process of finding the optimum incident angle by graphing method and makes the formula method the simplest method to find the optimum incident angle. Finally, the comparison of the interference intensity at the optimum incidence angle calculated by the improved method and normal incidence is given. It is found that the beam has a good suppression effect on the sub-peak when it is incident at the optimum incident angle calculated by the method in this paper.

Ricochet of High Speed Aluminium Projectiles From a Steel Plate

2016 ◽  
Author(s):  
Bakhtier Farouk ◽  
Steven B. Segletes
Keyword(s):  
High Speed ◽  
Steel Plate ◽  
Numerical Study ◽  
Incident Angle ◽  
Target Material ◽  
Numerical Results ◽  
Angle Of Incidence ◽  
Velocity Effect ◽  
Impact Angles ◽  
The Impact

A ricochet is a rebound, bounce or skip off a surface, particularly in the case of a projectile (a bullet). Many ricochets are accidental and while the force of the deflection decelerates the projectile, it can still be energetic and almost as lethal as before the deflection. The likelihood of ricochet is dependent on many factors, including projectile shape, projectile material, spin, velocity (and distance), target material and the angle of incidence. A numerical study on aluminum projectiles ricocheting off a steel plate is presented in this paper. The numerical package LS-DYNA is used to model the process of the impact of aluminum projectile on a steel plate. The simulations are carried out for a given range of projectile velocity (250 m/s to 1500 m/s) with varying impact angles. From the numerical results the ricochet angle and the ricochet velocity is predicted in terms of the incident angle and the incident velocity. The impact velocity effect on the ricochet phenomenon is studied. The numerical results are compared with available analytical solutions of the ricochet problem available in the literature.

Electron Channeling Patterns

1977 ◽  
Vol 35 ◽  
pp. 12-13
Author(s):  
David C. Joy
Keyword(s):  
Electron Diffraction ◽  
Incidence Angle ◽  
Photographic Plate ◽  
Diffraction Effect ◽  
Angle Of Incidence ◽  
Bulk Single Crystal ◽  
Time Resolved ◽  
Electron Channeling ◽  
Spatially Resolved ◽  
Large Bulk

Electron channeling patterns (ECP) were first found by Coates (1967) while observing a large bulk, single crystal of silicon in a scanning electron microscope. The geometric pattern visible was shown to be produced as a result of the changes in the angle of incidence, between the beam and the specimen surface normal, which occur when the sample is examined at low magnification (Booker, Shaw, Whelan and Hirsch 1967).A conventional electron diffraction pattern consists of an angularly resolved intensity distribution in space which may be directly viewed on a fluorescent screen or recorded on a photographic plate. An ECP, on the other hand, is produced as the result of changes in the signal collected by a suitable electron detector as the incidence angle is varied. If an integrating detector is used, or if the beam traverses the surface at a fixed angle, then no channeling contrast will be observed. The ECP is thus a time resolved electron diffraction effect. It can therefore be related to spatially resolved diffraction phenomena by an application of the concepts of reciprocity (Cowley 1969).

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