Simulation of Fluttering and Autorotation Motion of Vertically Hinged Flat Plate

2015 ◽  
Author(s):  
Ali Bakhshandeh Rostami ◽  
Antonio Carlos Fernandes
Keyword(s):  
Reynolds Number ◽  
Flat Plate ◽  
Dimensional Analysis ◽  
Time Domain ◽  
Rotational Motion ◽  
Small Amplitude ◽  
Transition Point ◽  
Vertical Axis ◽  
The Body ◽  
Rotating Plate

This paper is dedicated to the simulation of fluttering (oscillatory) and tumbling (rotational) phenomenon that may occur during the flow induced rotation in the water or air current. Fluttering is the oscillation of body about an axis and the tumbling, better called here as autorotation, is a name given to the case when the body turns continuously around the axis. This work describes the simulation of these phenomena by a nonlinear time domain code on freely rotating plate about a fixed vertical axis. The dimensional analysis proves that the rotational motion induced by flow is governed essentially by the dimensionless moment of inertia (I*) and Reynolds number. For Reynolds number less than 15000, plate experiences small amplitude fluttering motion that is independent of I*. It is shown that by increasing I* the fluttering bifurcates to autorotation, with a transition point that is approximately independent of Reynolds number and is such that I*=0.083.

Flow Induced Fluttering and Autorotation of a Hinged Vertical Flat Plate

2012 ◽  
Author(s):  
Antonio Carlos Fernandes ◽  
Sina Mirzaei Sefat
Keyword(s):  
Reynolds Number ◽  
Initial Conditions ◽  
Vertical Axis ◽  
Moment Of Inertia ◽  
Chaotic Oscillations ◽  
Uniform Current ◽  
The Stability ◽  
Rotation Motion ◽  
Rotating Plate ◽  
Vertical Flat Plate

This paper addresses the investigations on fluttering and autorotation motions which may occur in the interaction of uniform current and freely rotating plate about a fixed vertical axis. The autorotation is a name given to the case that the plate turns continuously about the vertical axis and the fluttering motion is the periodic or chaotic oscillations of the plate around the vertical axis. According to the dimensional analysis the motion in flow induced rotation motion is governed essentially by dimensionless moment of inertia, Reynolds number and initial conditions. Certain combinations define the stability boundaries between fluttering and autorotation. Hence, a bifurcation diagram was prepared by the experiments to classify different states observed the small fluttering, fluttering and autorotation based on different Reynolds number and dimensionless moment of inertia.

A Closed Formula for the Drag of a Flat Plate with Transition in the Absence of a Pressure Gradient

1960 ◽  
Vol 64 (589) ◽  
pp. 38-39 ◽  
Author(s):  
A. R. Collar
Keyword(s):  
Reynolds Number ◽  
Pressure Gradient ◽  
Flat Plate ◽  
Transition Point ◽  
Free Stream ◽  
Analytical Form ◽  
Stream Velocity ◽  
Closed Formula ◽  
Friction Drag ◽  
Do So

Most University students of fluid mechanics are familiar with the problem of the evaluation of the skin friction drag of a flat plate in the absence of a pressure gradient: transition is specified, usually by the free stream velocity and the transition point, or directly by the transition Reynolds number. The solution is normally obtained numerically: so far as the writer is aware, the processes used have not been written down in closed analytical form, though to do so presents no difficulty.

scholarly journals Rotational Maneuvers of Copepod Nauplii at Low Reynolds Number

Fluids ◽  
2020 ◽  
Vol 5 (2) ◽  
pp. 78
Author(s):  
Kacie T. M. Niimoto ◽  
Kyleigh J. Kuball ◽  
Lauren N. Block ◽  
Petra H. Lenz ◽  
Daisuke Takagi
Keyword(s):  
Reynolds Number ◽  
Rotational Motion ◽  
High Speed ◽  
The Body ◽  
Three Dimensions ◽  
Linear Path ◽  
Physical Mechanisms ◽  
High Speed Video ◽  
Video Observations ◽  
Principal Axes

Copepods are agile microcrustaceans that are capable of maneuvering freely in water. However, the physical mechanisms driving their rotational motion are not entirely clear in small larvae (nauplii). Here we report high-speed video observations of copepod nauplii performing acrobatic feats with three pairs of appendages. Our results show rotations about three principal axes of the body: yaw, roll, and pitch. The yaw rotation turns the body to one side and results in a circular swimming path. The roll rotation consists of the body spiraling around a nearly linear path, similar to an aileron roll of an airplane. We interpret the yaw and roll rotations to be facilitated by appendage pronation or supination. The pitch rotation consists of flipping on the spot in a maneuver that resembles a backflip somersault. The pitch rotation involved tail bending and was not observed in the earliest stages of nauplii. The maneuvering strategies adopted by plankton may inspire the design of microscopic robots, equipped with suitable controls for reorienting autonomously in three dimensions.

Experimental Investigation of Flow Induced Rotation of Hinged Plates With Shapes to Avoid Fluttering

2011 ◽  
Author(s):  
Antonio Carlos Fernandes ◽  
Sina Mirzaei Sefat ◽  
Fabio Moreira Coelho ◽  
Amanda Silva Albuquerque
Keyword(s):  
Experimental Investigation ◽  
Flat Plate ◽  
Flow Velocity ◽  
Natural Frequency ◽  
Dimensional Analysis ◽  
Vertical Axis ◽  
Incoming Flow ◽  
Stabilizing Effect ◽  
Plate Width ◽  
Angle Of Rotation

This paper addresses the flow induced rotation phenomena of plates hinged to allow flow induced rotating about their vertical axis. Different transversal shape configurations are studied. The aim of this study is to simplify the fluttering problem that may occur with falling objects in water during installation of offshore devices. The investigation intent is to propose an optimized configuration for stabilizing the fluttering motion of pendulous installation method of manifolds. The experiments and dimensional analysis confirmed that natural frequency is linearly proportional to the incoming flow velocity and inversely proportional to the flat plate width, and also the equivalent harmonic angle of rotation for small oscillation angles is approximately constant in different velocities. Experiments show that the bluffer plates (plate with two stabilizers and plate with stabilizers and nose), by increasing of period of rotation and also decreasing of equivalent harmonic angle of rotation have stabilizing effect in the fluttering motion of falling objects.

A New “Number” for Aircraft with Power-Augmented Circulation

1965 ◽  
Vol 69 (650) ◽  
pp. 137-137
Author(s):  
C. F. Toms
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Dimensional Analysis ◽  
Relative Motion ◽  
The Body ◽  
Several Variables ◽  
Function Of Several Variables

The Familiar process of dimensional analysis for aerodynamics equates a force to a function of several variables liable to affect it, in terms of the dimensions M, L, T, and yields the numbers known as the Reynolds number and the Mach number of the flow. These numbers are generally regarded as useful and sufficient means of denoting the regimes of flow in conventional circumstances, where the force developed on a body results solely from the relative motion between the body and a mass of fluid.

scholarly journals Single-Photon Detection Module Based on Large-Area Silicon Photomultipliers for Time-Domain Diffuse Optics

Instruments ◽  
2021 ◽  
Vol 5 (2) ◽  
pp. 18
Author(s):  
Fabio Acerbi ◽  
Anurag Behera ◽  
Alberto Dalla Mora ◽  
Laura Di Sieno ◽  
Alberto Gola
Keyword(s):  
Time Resolution ◽  
Time Domain ◽  
Single Photon ◽  
Building Blocks ◽  
The Body ◽  
Single Photon Detection ◽  
Silicon Photomultipliers ◽  
Photon Detection ◽  
Instrument Response Function ◽  
Diffuse Optics

Silicon photomultipliers (SiPM) are pixelated single-photon detectors combining high sensitivity, good time resolution and high dynamic range. They are emerging in many fields, such as time-domain diffuse optics (TD-DO). This is a promising technique in neurology, oncology, and quality assessment of food, wood, and pharmaceuticals. SiPMs can have very large areas and can significantly increase the sensitivity of TD-DO in tissue investigation. However, such improvement is currently limited by the high detector noise and the worsening of SiPM single-photon time resolution due to the large parasitic capacitances. To overcome such limitation, in this paper, we present two single-photon detection modules, based on 6 × 6 mm2 and 10 × 10 mm2 SiPMs, housed in vacuum-sealed TO packages, cooled to −15 °C and −36 °C, respectively. They integrate front-end amplifiers and temperature controllers, being very useful instruments for TD-DO and other biological and physical applications. The signal extraction from the SiPM was improved. The noise is reduced by more than two orders of magnitude compared to the room temperature level. The full suitability of the proposed detectors for TD-DO measurements is outside the scope of this work, but preliminary tests were performed analyzing the shape and the stability of the Instrument Response Function. The proposed modules are thus fundamental building blocks to push the TD-DO towards deeper investigations inside the body.

scholarly journals Movement of a finite body in channel flow

2016 ◽  
Vol 472 (2191) ◽  
pp. 20160164 ◽  
Author(s):  
Frank T. Smith ◽  
Edward R. Johnson
Keyword(s):  
Reynolds Number ◽  
Channel Flow ◽  
Flow Instability ◽  
Flow Direction ◽  
Finite Size ◽  
The Body ◽  
Thin Body ◽  
Shear Stresses ◽  
Unsteady Interaction ◽  
High Reynolds

A body of finite size is moving freely inside, and interacting with, a channel flow. The description of this unsteady interaction for a comparatively dense thin body moving slowly relative to flow at medium-to-high Reynolds number shows that an inviscid core problem with vorticity determines much, but not all, of the dominant response. It is found that the lift induced on a body of length comparable to the channel width leads to differences in flow direction upstream and downstream on the body scale which are smoothed out axially over a longer viscous length scale; the latter directly affects the change in flow directions. The change is such that in any symmetric incident flow the ratio of slopes is found to be cos ⁡ ( π / 7 ) , i.e. approximately 0.900969, independently of Reynolds number, wall shear stresses and velocity profile. The two axial scales determine the evolution of the body and the flow, always yielding instability. This unusual evolution and linear or nonlinear instability mechanism arise outside the conventional range of flow instability and are influenced substantially by the lateral positioning, length and axial velocity of the body.

Analysis of the First Order and Slowly Varying Motions of an Axisymmetric Floating Body in Bichromatic Waves

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
João Pessoa ◽  
Nuno Fonseca ◽  
C. Guedes Soares
Keyword(s):  
Vertical Cylinder ◽  
Vertical Axis ◽  
Second Order ◽  
The Body ◽  
Floating Body ◽  
Drift Motion ◽  
First Order ◽  
Motion Responses ◽  
Simple Geometry ◽  
Good Agreement

The paper presents an experimental and numerical investigation on the motions of a floating body of simple geometry subjected to harmonic and biharmonic waves. The experiments were carried out in three different water depths representing shallow and deep water. The body is axisymmetric about the vertical axis, like a vertical cylinder with a rounded bottom, and it is kept in place with a soft mooring system. The experimental results include the first order motion responses, the steady drift motion offset in regular waves and the slowly varying motions due to second order interaction in biharmonic waves. The hydrodynamic problem is solved numerically with a second order boundary element method. The results show a good agreement of the numerical calculations with the experiments.

Plumpness Analysis of Indicator Diagram for Vehicle Damper

2013 ◽  
Vol 415 ◽  
pp. 582-585
Author(s):  
Xing Xu ◽  
Zhen Cui ◽  
Jin Chao Zhang
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Dynamic Load ◽  
Performance Indicators ◽  
Load Distribution ◽  
The Body ◽  
Quantitative Index ◽  
Indicator Diagram ◽  
Vehicle Demand ◽  
Mathematical Relationships

According to the indicator diagram of damper, the indicator diagram plumpness was proposed as a quantitative index, and its mathematical relationships with the sprung mass acceleration, suspension dynamic travel and tire dynamic load were built. Moreover, the influence of the total area on suspension characteristics was analyzed in time domain and frequency domain. The results show that, the increase of the indicator diagram plumpness can effectively restrain the variation of suspension dynamic travel and tire dynamic load, meanwhile, the body acceleration will be enlarged. Excessive indicator diagram plumpness also affects the dynamic tire load distribution in frequency domain, and it will decrease the driving security. Therefore, it should be reasonably selected from the performance indicators, which is based on the requirement of vehicle demand in the design process.

scholarly journals The Profile Drag of Yawed Wings of Infinite Span

1951 ◽  
Vol 3 (3) ◽  
pp. 211-229 ◽  
Author(s):  
A.D. Young ◽  
T.B. Booth
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Drag Coefficient ◽  
Experimental Evidence ◽  
Flat Plate ◽  
Transition Point ◽  
Reynolds Numbers ◽  
External Pressure ◽  
Basic Assumptions ◽  
Angle Of Yaw

SummaryA method is developed for calculating the profile drag of a yawed wing of infinite span, based on the assumption that the form of the spanwise distribution of velocity in the boundary layer, whether laminar or turbulent, is insensitive to the chordwise pressure distribution. The form is assumed to be the same as that accepted for the boundary layer on an unyawed plate with zero external pressure gradient. Experimental evidence indicates that these assumptions are reasonable in this context. The method is applied to a flat plate and the N.A.C.A. 64-012 section at zero incidence for a range of Reynolds numbers between 106 and 108, angles of yaw up to 45°, and a range of transition point positions. It is shown that the drag coefficients of a flat plate varies with yaw as cos½ Λ (where Λ is the angle of yaw) if the boundary layer is completely laminar, and it varies as if the boundary layer is completely turbulent. The drag coefficient of the N.A.C.A. 64-012 section, however, varies closely as cos½ Λ for transition point positions between 0 and 0.5 c. Further calculations on wing sections of other shapes and thicknesses and more detailed experimental checks of the basic assumptions at higher Reynolds numbers are desirable.

Sign in / Sign up

Export Citation Format

Share Document