scholarly journals Applying potential-based panel method for steady flow analysis across a wing with finite span

2019 ◽  
Vol 31 ◽  
pp. 125-136
Author(s):  
Konstantin Metodiev
Keyword(s):  
Steady Flow ◽  
Potential Function ◽  
Collocation Point ◽  
Source Code ◽  
Flow Analysis ◽  
Boundary Surface ◽  
Arbitrary Point ◽  
The Body ◽  
Layer Potential ◽  
Submerged Body

In the paper hereby, an incompressible irrotational steady flow across a submerged body with finite dimensions will be studied. For this purpose, it is necessary to solve Laplace’s differential equation about a potential function in order to obtain the conservative velocity vector field. A general solution to the problem utilizing the Green identity implies the double layer potential function at an arbitrary point not belonging to the boundary surface. The potential is expressed by source/sink and doublet singularities distributed over the body surface and a wake attached to the trailing edge. The wake ensures that the Kutta condition is fulfilled. The submerged body geometry is approximated further by quadrilateral panels in order to compute the surface integrals for each panel exactly. To form a linear non-homogenous algebraic system, it is essentially to compute each panel influence to a collocation point of interest. The obtained coefficient matrix is diagonally dominant. The system is solved iteratively by means of the Gauss-Seidel method. The goal is development of a non-proprietary source code in order to work out a solution to the stated problem. The developed source code is authentic. Auxiliary libraries have not been used. Validation case and numerical results are depicted and discussed in the paper.

scholarly journals Combination of an Improved FRF-Based Substructure Synthesis and Power Flow Method with Application to Vehicle Axle Noise Analysis

2008 ◽  
Vol 15 (1) ◽  
pp. 51-60 ◽  
Author(s):  
C.Q. Liu
Keyword(s):  
Power Flow ◽  
Noise Analysis ◽  
Flow Analysis ◽  
Synthesis Method ◽  
The Body ◽  
Vehicle Body ◽  
Total System ◽  
Simple Formulation ◽  
Substructure Synthesis ◽  
Fea Model

In this paper, an improved FRF-based substructure synthesis method combined with power flow analysis is presented and is used for performing a vehicle axle noise analysis. The major transfer paths of axle noise transmitted from chassis to vehicle body are identified and ranked based on power flows transmitted through bushings between the chassis and body. To calculate the power flows, it is necessary to know the reaction forces and the vibrations at the bushing locations on the body side. To this end, the body is represented in terms of experimentally derived frequency response functions (FRF's) at the bushing locations, and the FRF's are coupled with the FEA model of the chassis for performing a total system dynamic analysis. This paper also describes how the FRF's of the vehicle body and the frequency dependent stiffness data of the bushings can be combined together with a simple formulation to better represent the dynamic characteristics of a full vehicle. A classical example is used to illustrates the concept of the method, and the method is then applied to a vehicle axle noise analysis with detailed procedure. The theoretical predictions are compared with experimentally measured results. Good correlation has been obtained.

Generation of steady longitudinal vortices in hypersonic boundary layer

2013 ◽  
Vol 729 ◽  
pp. 702-731 ◽  
Author(s):  
A. I. Ruban ◽  
M. A. Kravtsova
Keyword(s):  
Boundary Layer ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Viscosity Coefficient ◽  
Momentum Equation ◽  
The Body ◽  
Nonlinear Behaviour ◽  
Hypersonic Boundary Layer ◽  
Stagnation Temperature ◽  
Characteristic Distance

AbstractIn this paper we study the three-dimensional perturbations produced in a hypersonic boundary layer by a small wall roughness. The flow analysis is performed under the assumption that the Reynolds number, $R{e}_{0} = {\rho }_{\infty } {V}_{\infty } L/ {\mu }_{0} $, and Mach number, ${M}_{\infty } = {V}_{\infty } / {a}_{\infty } $, are large, but the hypersonic interaction parameter, $\chi = { M}_{\infty }^{2} R{ e}_{0}^{- 1/ 2} $, is small. Here ${V}_{\infty } $, ${\rho }_{\infty } $ and ${a}_{\infty } $ are the flow velocity, gas density and speed of sound in the free stream, ${\mu }_{0} $ is the dynamic viscosity coefficient at the ‘stagnation temperature’, and $L$ is the characteristic distance the boundary layer develops along the body surface before encountering a roughness. We choose the longitudinal and spanwise dimensions of the roughness to be $O({\chi }^{3/ 4} )$ quantities. In this case the flow field around the roughness may be described in the framework of the hypersonic viscous–inviscid interaction theory, also known as the triple-deck model. Our main interest in this paper is the nonlinear behaviour of the perturbations. We study these by means of numerical solution of the triple-deck equations, for which purpose a modification of the ‘skewed shear’ technique suggested by Smith (United Technologies Research Center Tech. Rep. 83-46, 1983) has been used. The technique requires global iterations to adjust the viscous and inviscid parts of the flow. Convergence of such iterations is known to be a major problem in viscous–inviscid calculations. In order to achieve improved stability of the method, both the momentum equation for the viscous part of the flow, and the equations describing the interaction with the flow outside the boundary layer, are treated implicitly in this study. The calculations confirm the fact that in this sort of flow the perturbations are capable of propagating upstream in the boundary layer, resulting in a perturbation field which surrounds the roughness on all sides. We found that the perturbations decay rather fast with the distance from the roughness everywhere except in the wake behind the roughness. We found that if the height of the roughness is small, then the perturbations also decay in the wake, though much more slowly than outside the wake. However, if the roughness height exceeds some critical value, then two symmetric counter-rotating vortices form in the wake. They appear to support themselves and grow as the distance from the roughness increases.

The Structure of Trichocysts in Paramecium Caudatum

1972 ◽  
Vol 11 (3) ◽  
pp. 899-929
Author(s):  
L. H. BANNISTER
Keyword(s):  
Amorphous Matrix ◽  
Boundary Surface ◽  
The Body ◽  
Single Type ◽  
Apical Region ◽  
Paramecium Caudatum ◽  
Lower Phase ◽  
Microscopic Appearance ◽  
Outer Sheath ◽  
Crystalline Matrix

The structure of undischarged and discharged trichocysts has been examined in Paramecium caudatum, and their light-microscopic appearance compared with their fine-structural organization. In living specimens undischarged trichocysts appear to be of a single type with a unimodal variation in length about a mean of 3.7 µm. When fixed for electron microscopy or compressed beneath a coverslip many of the trichocysts expand within the cell, giving rise to a variety of different forms of lower phase density. Ultrastructurally the undischarged trichocyst consists of at least 10 different components: these include a mesh-like sheath surrounding the body of the organelle; an inner and an outer sheath enclosing the tip, the inner sheath being made up of 4 spiralling envelopes with a square net substructure, and the outer sheath being formed of a dense amorphous matrix containing longitudinal microtubules and scattered fine filaments; a boundary surface to the outer sheath; a membranous trichocyst sac the apical region of which is surrounded by a cylinder of microtubules joined to each other with dense material; and lastly, the crystalline matrix of the trichocyst body and tip. This crystalline appearance is apparently related to the presence of a loosely interwoven complex of fine filaments which form a highly regular pattern of unit structures repeating at 16-nm intervals. In extended trichocysts the 60-nm banding pattern of the body is also composed of fine filaments arranged in a different, elongated manner in 2 distinct and alternating patterns which are taken to be 2 views of the same structure. Measurements indicate that when trichocysts extend they elongate by a factor of from 6 to 8. It is proposed that the crystalline pattern of the unextended trichocyst body transforms into the extended form by a simple rearrangement of the constituent filaments accompanied by their elongation. Possible models of the undischarged and discharged states of organization are suggested.

scholarly journals Application of Two Shallow Water Models to Steady Flow Analysis in a Vegetated Agricultural Drainage Canal

2013 ◽  
Vol 19 (2) ◽  
pp. 35-41 ◽  
Author(s):  
Hidekazu Yoshioka ◽  
Nobuhiko Kinjo ◽  
Ayaka Wakazono ◽  
Koichi Unami ◽  
Masayuki Fujihara
Keyword(s):  
Shallow Water ◽  
Steady Flow ◽  
Flow Analysis ◽  
Agricultural Drainage ◽  
Drainage Canal ◽  
Shallow Water Models ◽  
Water Models

A Study of the Transient Pitching Oscillations of a Ship

1959 ◽  
Vol 3 (01) ◽  
pp. 22-30
Author(s):  
Paul Golovato
Keyword(s):  
Vertical Plane ◽  
The Body ◽  
Plane Symmetry ◽  
Moment Equations ◽  
Longitudinal Modes ◽  
Second Order Differential Equations ◽  
Stability Derivatives ◽  
Submerged Body ◽  
Constant Coefficients ◽  
Instantaneous Values

The motions of a deeply submerged body with vertical-plane symmetry, e.g., a submarine, are commonly treated in a manner completely analogous to that used for aircraft motions. The body is assumed to have its lateral and longitudinal modes uncoupled. The small motions are described by a set of force-and-moment equations which are linear, second-order differential equations with constant coefficients. These proportionality constants ("stability derivatives") relate the forces and moments to the instantaneous values of the position, velocity, and acceleration of the body. They are generally experimentally determined in the wind or water tunnel, and the controlled or uncontrolled motions of the craft are predicted based thereon.

A System to Measure Turbulent Lengthscales on Submerged Bodies of Revolution

2017 ◽  
Author(s):  
Christopher J. Chesnakas ◽  
Daniel R. Cadel
Keyword(s):  
Laser Doppler Velocimetry ◽  
Arrival Time ◽  
Noise Removal ◽  
The Body ◽  
Doppler Velocimetry ◽  
Body Of Revolution ◽  
Sampled Data ◽  
Bodies Of Revolution ◽  
Submerged Body ◽  
Cross Correlations

A system has been developed to measure the turbulent lengthscales in the flow about a submerged body of revolution. The system consists of two Laser Doppler Velocimetry (LDV) probes mounted inside the body of revolution with the beams projected outside of the body through conformal windows. The measurement volumes of the two probes can be independently positioned within a plane perpendicular to the body axis. The probes are used to measure velocity time series at various spacings in the flow field. Auto- and cross-correlations are computed for each measurement pair, from which integral lengthscales are then found. Measurements are compared to canonical data from a turbulent free shear jet. In this paper, the system is described and its theory of operation detailed. Methods of computing the velocity correlations from the random-arrival-time LDV measurements are presented, and a new noise-removal scheme for non-uniformly sampled data is introduced. Six methods for calculating the integral lengthscale from autocorrelation data are reviewed, and the results discussed for the present jet data measured with LDV.

Nonlinear Aspects of Subcritical Shallow-Water Flow Past Two-Dimensional Obstructions

1978 ◽  
Vol 22 (04) ◽  
pp. 203-211
Author(s):  
Nils Salvesen ◽  
C. von Kerczek
Keyword(s):  
Free Surface ◽  
Shallow Water ◽  
Flow Problem ◽  
Free Stream ◽  
The Body ◽  
Two Dimensional ◽  
Third Order ◽  
Submerged Body ◽  
The Mean ◽  
The Waves

Some nonlinear aspects of the two-dimensional problem of a submerged body moving with constant speed in otherwise undisturbed water of uniform depth are considered. It is shown that a theory of Benjamin which predicts a uniform rise of the free surface ahead of the body and the lowering of the mean level of the waves behind it agrees well with experimental data. The local steady-flow problem is solved by a numerical method which satisfies the exact free-surface conditions. Third-order perturbation formulas for the downstream free waves are also presented. It is found that in sufficiently shallow water, the wavelength increases with increasing disturbance strength for fixed values of the free-stream-Froude number. This is opposite to the deepwater case where the wavelength decreases with increasing disturbance strength.

Training the Body Politic: Networked Masculinity and the ‘War on Terror’ in Hollywood Film

2016 ◽  
Author(s):  
Adam Knee
Keyword(s):  
Comparative Analysis ◽  
Detailed Analysis ◽  
War On Terror ◽  
Source Code ◽  
Body Politic ◽  
The Body ◽  
James Bond ◽  
Hollywood Film ◽  
Hollywood Films ◽  
Political Perspective

Adam Knee continues this discussion of the action/adventure genre in Chapter Seven, "Training the Body Politic: Networked Masculinity and the 'War on Terror' in Hollywood Film", offering a detailed analysis of the representation of masculinity and agency in two Hollywood films, Unstoppable (2010) and Source Code (2011), which exhibit striking similarities at a range of levels, from their narratives to deeper structures of gendered character function, theme, and geo-political perspective that, he contends, are a manifestation of distinctly post-9/11 American concerns. Like Vincent M. Gaine's chapter on James Bond, Knee analyses both the variations inherent in the genre in the wake of 9/11 and the consistencies of the parameters of American mainstream film, and, more specifically, a developing conceptualization of modes of disciplined masculinity necessitated by the nation’s 'War on Terror' narrative. Knee then concludes with a comparative analysis of a pre-9/11 film and its post-9/11 remake in which these parameters are brought to the fore: the original Paul Verhoeven RoboCop (1987) and RoboCop (2014) directed by José Padilha.

Interaction of rarefaction waves with area reductions in ducts

1983 ◽  
Vol 137 ◽  
pp. 285-305 ◽  
Author(s):  
J. J. Gottlieb ◽  
O. Igra
Keyword(s):  
Steady Flow ◽  
Rarefaction Wave ◽  
Gas Flow ◽  
Flow Analysis ◽  
Inviscid Flow ◽  
Rarefaction Waves ◽  
Area Reduction ◽  
Random Choice Method ◽  
Wave Patterns ◽  
The One

The interaction of a rarefaction wave with a gradual monotonic area reduction of finite length in a duct, which produces transmitted and reflected rarefaction waves and other possible rarefaction and shock waves, was studied both analytically and numerically. A quasi-steady flow analysis which is analytical for an inviscid flow of a perfect gas was used first to determine the domains of and boundaries between four different wave patterns that occur at late times, after all local transient disturbances from the interaction process have subsided. These boundaries and the final constant strengths of the transmitted, reflected and other waves are shown as a function of both the incident rarefaction-wave strength and area-reduction ratio, for the case of diatomic gases and air with a specific-heat ratio of 7/5. The random-choice method was then used to solve numerically the conservation equations governing the one-dimensional non-stationary gas flow for many different combinations of rarefaction-wave strengths and area-reduction ratios. These numerical results show clearly how the transmitted, reflected and other waves develop and evolve with time, until they eventually attain constant strengths, in agreement with quasi-steady flow predictions for the asymptotic wave patterns. Note that in all of this work the gas in the area reduction is initially at rest.

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