Flow Induced Rotation of a Flat Plate Subjected in Uniform Current Based on the Streamline Theory

2011 ◽  
Author(s):  
Sina Mirzaei Sefat ◽  
Antonio Carlos Fernandes
Keyword(s):  
Flat Plate ◽  
Natural Frequency ◽  
Moment Coefficient ◽  
Trailing Edges ◽  
Free Streamlines ◽  
Two Dimensional Flow ◽  
Sharp Edges ◽  
Uniform Current ◽  
Flow Configurations ◽  
The Moment

This work describes the behavior of a vertical flat plate free to rotate in uniform current. The intention of this research is to study the fluttering problem that may occur with falling objects in water such as a manifold during the pendulous installation method (PIM). The free streamline theory is applied here to investigate the steady, two-dimensional flow at a given angle of attack past a flat plate with a fully developed wake. The leading and trailing edges of the plate are assumed to be sharp and the flow configurations are such that the free streamlines separate from the plate at these sharp edges, the thickness of the flat plate is assumed to be of zero. The Roshko’s model will be used to approximate the wake far downstream. The moment coefficient formulation has been calculated for different angles of attack yielding good accuracy with experimental results. This includes the existence of a natural frequency for small amplitude oscillations. The free-streamline theory confirms that the natural frequency is linearly proportional to the incoming flow velocity.

The Research on Natural Characteristic and Eigensensitivity of Ravingneaux Compound Planetary Gear Sets

2013 ◽  
Vol 446-447 ◽  
pp. 590-596
Author(s):  
Bo Qian ◽  
Shi Jing Wu
Keyword(s):  
Natural Frequency ◽  
Planetary Gear ◽  
Torsional Stiffness ◽  
Ring Gear ◽  
Vibration Model ◽  
Planetary Gear Sets ◽  
Planet Gear ◽  
Natural Characteristic ◽  
Gear Ring ◽  
The Moment

The dynamic model of Ravingneaux compound planetary gear sets has been built. Then the Natural frequency and vibration model have been solved in the Ravingneaux compound planetary gear sets. The eigensensitivity to parameters have been researched based on the dynamical model. The varying trend of natural frequency according to the varying of parameters have been researched, which include gear mass (sun gear, ring gear , or planet gear), the moment of inertia of gears, the support stiffness , the torsional stiffness.

scholarly journals Experimental Investigation of the Ground Effect of WIG Craft—NEW1 Model

Proceedings ◽  
2020 ◽  
Vol 39 (1) ◽  
pp. 17
Author(s):  
Sakornsin ◽  
Thipyopas ◽  
Atipan
Keyword(s):  
Lift Coefficient ◽  
Ground Surface ◽  
Ground Effect ◽  
Aerodynamic Characteristics ◽  
Scale Model ◽  
Negative Slope ◽  
Stream Velocity ◽  
Longitudinal Stability ◽  
Moment Coefficient ◽  
The Moment

Navy Experimental Wing-in-Ground-Effect (WIG) craft namely as NEW1, is the first version of 2-seated WIG craft which has been designed and developed by Royal Thai Navy since 2017. This experimental research is a part of the NEW1 project which aims to investigate the aerodynamic characteristics and aspects of the flow passing through the WIG craft model when in ground effect. In the experiment, the WIG craft—NEW1 of 1:15 scale model is tested in a close circuit wind tunnel of 1 m × 1 m test section at Kasetsart University. The tests are conducted at the free stream velocity of 40 m/s or Reynolds number of 280,000, at angles of attack ranging from −9° to 21°, and at the wing to ground distances ranging from 5.0 C to 0.3 C. The measurement of 6-DoF of forces and moments and pressure distributions on the ground surface underneath the WIG craft model are made during the tests. The results show that the ground has significant effects on the aerodynamic characteristics of the WIG craft model when the wing to ground distance is less than its mean chord. It was found that when the model move from 5.0 C (out of ground effect) to 0.3 C, the lift coefficient increases up to 15.7%, the drag coefficient decreases up to 5.6%, and the lift to drag ratio increases 33.4%. The proximity of the model to the ground also affects the longitudinal stability of the model. The moment coefficient curves against angle of attack has negative slope for both in and out of ground effect indicating favorable longitudinal stability. However, it was found that the aerodynamic center move further aft toward the trailing edge when the model move closer to the ground.

Influence of the pressure relief door area and aspect ratio on discharge and force characteristics

2019 ◽  
Vol 92 (2) ◽  
pp. 107-116
Author(s):  
Shiyu Feng ◽  
Chenchen Wang ◽  
Xiaotian Peng ◽  
Yan Yan ◽  
Yang Deng ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Discharge Coefficient ◽  
Geometric Parameters ◽  
Pressure Relief ◽  
Thrust Coefficient ◽  
Content Type ◽  
Moment Coefficient ◽  
The Moment ◽  
Compartment Pressures ◽  
Force Characteristics

Purpose The purpose of this paper is to analyze the effects of the PRD geometric parameters, including the area and aspect ratio, on the discharge and force characteristics of pressure relief process under various plenum compartment pressures and Mach numbers. Design/methodology/approach Under various plenum compartment pressures and Mach numbers, the effect of the area and aspect ratio on the discharge and force characteristics of the PRD are numerically investigated via a three-dimensional steady Reynolds-averaged Navier–Stokes equations solver based on structured grid technology. Findings When the aspect ratio remains constant, the discharge coefficient CD, thrust coefficient CT and moment coefficient CM are not affected by the PRD. When the area is constant, the aspect ratio dramatically impacts the discharge and force characteristics because the aspect ratio increases, the discharge coefficient CD of the PRD decreases, and the thrust coefficient CT and the moment coefficient CM both increase. When the aspect ratio is 2, the discharge coefficient CD decreases by 14.7 per cent, the thrust coefficient CT increases by 10-15 per cent, and the moment coefficient CM increases by 10-23 per cent compared with when the aspect ratio is 1. Practical implications This study provides detailed data and conclusions for nacelle PRD researchers and actual engineering applications. Originality/value On the basis of considering the influence of operating conditions on the discharge and force characteristics of the nacelle PRD, the impact of geometric parameters, including the area and aspect ratio on the discharge and force characteristics is comprehensively considered.

Plate Shape Effect on the Performance of the Vertical Axis Auto Rotation Current Turbine (VAACT)

2014 ◽  
Author(s):  
Ali Bakhshandeh Rostami ◽  
Antonio Carlos Fernandes
Keyword(s):  
Flat Plate ◽  
High Efficiency ◽  
Vertical Axis ◽  
Speed Ratio ◽  
Shape Effect ◽  
Tip Speed Ratio ◽  
Upper Limit ◽  
Plate Shape ◽  
Uniform Current ◽  
Current Turbine

The present paper explores experimentally the performance of two types of hinged plates which rotate about vertical axis when submitted to uniform current. A flat plate configuration and also a flapped plate (say, S shape) configuration have been investigated. The Vertical axis Auto rotation Current Turbine (VAACT) is one degree of freedom system (free to rotate in yaw direction). It is shown that a high efficiency for S shape type can be obtained of the order of 30 percent while flat blade type reaches approximately to 7 percent. Upper limit of tip speed ratio for flat blade type has been expanded approximately 0.9 whereas S shape approaches 1.3.

A Study on Calculation Method of Natural Frequency for Rubber Damped Torsional Vibration Absorbers

2014 ◽  
Author(s):  
Wen-Bin Shangguan ◽  
Yumin Wei ◽  
Subhash Rakheja ◽  
Xu Zhao ◽  
Jun-wei Rong ◽  
...  
Keyword(s):  
Fractional Derivative ◽  
Natural Frequency ◽  
Dynamic Performance ◽  
Model Parameters ◽  
Dynamic Shear ◽  
Shear Properties ◽  
Rubber Ring ◽  
Constructive Models ◽  
Dynamic Performances ◽  
The Moment

The natural frequency is the key performance parameters of a rubber materials damper, and it is determined by the static and dynamic shear properties of the rubber materials (rubber ring) and the moment of inertia of the inertia ring. The rubber ring is usually in compression state, and its static and dynamic shear properties are dependent on its sizes, compression ratio and chemical ingredients. A special fixture is designed and used for measuring static and dynamic shear performance of a rubber ring under different compression ratios in the study. To characterize the shear static and dynamic performances of rubbers, three constructive models (Kelvin-Voigt, the Maxwell and the fractional derivative constitutive model) are presented and the method for obtaining the model parameters in the fractional derivative constructive models are developed using the measured dynamic performance of a rubber shear specimen. The natural frequency of a rubber materials damper is calculated using the fractional derivative to characterize the rubber ring of the damper, and the calculated frequencies are compared with the measurements.

Wind-tunnel tests of a tilt-rotor aircraft

2011 ◽  
Vol 115 (1167) ◽  
pp. 315-322 ◽  
Author(s):  
G. Gibertini ◽  
F. Auteri ◽  
G. Campanardi ◽  
C. Macchi ◽  
A. Zanotti ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Aircraft Design ◽  
Longitudinal Axis ◽  
Scale Model ◽  
Nonlinear Behaviour ◽  
Moment Coefficient ◽  
High Incidence ◽  
Aerodynamic Test ◽  
The Moment ◽  
Very High

Abstract A wide aerodynamic test campaign has been carried out on the tiltrotor aircraft ERICA at the Large Wind Tunnel of Politecnico di Milano by means of a modular 1:8 scale model in order to produce a dataset necessary to better understand the aerodynamic behaviour of the aircraft and to state its definitive design. The target of the tests was the measurement of the aerodynamic forces and moments in several different configurations and different attitudes. The test program included some conditions at very high incidence and sideslip angles that typically belong to the helicopter-mode flight envelope and measurements of forces on the tail and on the tilting wings. A large amount of data has been collected that will be very useful to refine the aircraft design. In general the aircraft aerodynamics do not present any critical problems, but further optimisation is still possible. From the viewpoint of drag in the cruise configuration, the sponsons of the landing gear seem to be worth some further design refinement since they are responsible for a 20% drag increase with respect to the pure fuselage configuration. On the contrary, the wing fairing has proved to work well when the aircraft longitudinal axis is aligned with the wind, providing just a slight drag increase. Two other interesting aspects are the quite nonlinear behaviour of the side force for the intermediate sideslip angles as well as the noticeable hysteresis in the moment coefficient at very high incidence angles.

The slow transverse motion of a flat plate through a non-diffusive stratified fluid

1971 ◽  
Vol 47 (1) ◽  
pp. 171-181 ◽  
Author(s):  
G. S. Janowitz
Keyword(s):  
Viscous Fluid ◽  
Shear Layer ◽  
Flat Plate ◽  
Kinematic Viscosity ◽  
Vertical Plate ◽  
The Body ◽  
Vertical Shear ◽  
Transverse Motion ◽  
Two Dimensional ◽  
Two Dimensional Flow

We consider the two-dimensional flow produced by the slow horizontal motion of a vertical plate of height 2b through a vertically stratified (ρ = ρ0(1 - βz)) non-diffusive viscous fluid. Our results are valid when U2 [Lt ] Ub/ν [Lt ] 1, where U is the speed of the plate and ν the kinematic viscosity of the fluid. Upstream of the body we find a blocking column of length 10−2b4/(Uν/βg. This column is composed of cells of closed streamlines. The convergence of these cells near the tips of the plate leads to alternate jets. The plate itself is embedded in a vertical shear layer of thickness (Uν/βg)1/3. In the upstream portion of this layer the vertical velocities are of order U and in the downstream portion of order Ub/(Uν/βg)1/3 ([Gt ] U). The flow is uniform and undisturbed downstream of this layer.

scholarly journals IX. Mathematical contributions to the theory of evolution.—XIX. Second supplement to a memoir on skew variation

1916 ◽  
Vol 216 (538-548) ◽  
pp. 429-457 ◽  
Keyword(s):  
Standard Deviation ◽  
Homogeneous Material ◽  
Fourth Moment ◽  
Frequency Distributions ◽  
Theory Of Evolution ◽  
Theoretical Frequency ◽  
Moment Coefficient ◽  
The Mean ◽  
The Moment ◽  
True Values

In a memoir presented to the Royal Society in 1894, I dealt with skew variation in homogeneous material. The object of that memoir was to obtain a series of curves such that one or other of them would agree with any observational or theoretical frequency curve of positive ordinates to the following extent :—(i) The areas should be equal; (ii) the mean abscissa or centroid vertical should be the same for the two curves; (iii) the standard deviation (or, what amounts to the same thing, the second moment coefficient) about this centroid vertical should be the same, and (iv) to (v) the third and fourth moment coefficients should also be the same. If μ s be the s th moment coefficient about the mean vertical, N the area, x ¯ be the mean abscissa, σ = √ μ 2 the standard deviation, β 1 = μ 3 2 / μ 2 3 , β 4 = μ 4 / μ 2 2 , then the equality for the two curves of N, x ¯ , σ, β 1 and β 2 leads almost invariably in the case of frequency to excellency of fit. Indeed, badness of fit generally arises from either heterogeniety, or the difficulty in certain cases of accurately determining from the data provided the true values of the moment coefficients, e. g ., especially in J- and U-shaped frequency distributions, or distributions without high contact at the terminals ; here the usual method of correcting the raw moments for sub-ranges of record fails. Having found a curve which corresponded to the skew binomial in the same manner as the normal curve of errors to the symmetrical binomial with finite index, it occurred to me that a development of the process applied to the hypergeometrical series would achieve the result I was in search of, i. e ., a curve whose constants would be determined by the observational values of N, x ¯ , σ, β 1 and β 2 .

A Schwarz-Christoffel Method for Generating Two-Dimensional Flow Grids

1985 ◽  
Vol 107 (3) ◽  
pp. 330-337 ◽  
Author(s):  
K. P. Sridhar ◽  
R. T. Davis
Keyword(s):  
Internal Flow ◽  
Mesh Size ◽  
Simple Expression ◽  
Two Dimensional ◽  
Two Dimensional Flow ◽  
Mesh Spacing ◽  
Flow Configurations ◽  
External Flows ◽  
Christoffel Transformation ◽  
High Degree

A new coordinate generation technique, developed by Davis for external flows, is extended to allow for accurate grid generation for a variety of complex internal flow configurations. The approach is based on numerical integration of the Schwarz-Christoffel transformation for polygonal surfaces. It is shown to be second-order accurate with mesh size due to analytic treatment of boundary singularities. The method is flexible enough to allow for treatment of severe internal geometries, for a high degree of control of mesh spacing, and for generation of either orthogonal or nonorthogonal grids. In addition, this technique directly provides the two-dimensional incompressible potential flow solution for internal flows, as well as a simple expression for calculating the grid metric coefficients. Sample cases include symmetric and asymmetric channel, diffuser, and cascade flows.

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