Flow Interaction Near the Tail of a Body of Revolution—Part 2: Iterative Solution for Flow Within and Exterior to Boundary Layer and Wake

1976 ◽  
Vol 98 (3) ◽  
pp. 538-546 ◽  
Author(s):  
A. Nakayama ◽  
V. C. Patel ◽  
L. Landweber
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Potential Flow ◽  
Reasonable Agreement ◽  
Complete Solution ◽  
Iterative Solution ◽  
The Body ◽  
External Potential ◽  
Iterative Technique ◽  
Body Of Revolution

This part deals with the calculation of the flow within the attached boundary layer and the wake of a body of revolution and its interaction with the external potential flow which was treated in Part 1. The iterative technique described in Part 1 is used to obtain a complete solution to the flow in the neighborhood of the tail of the body. The results of the calculations are compared with two sets of experimental data and reasonable agreement is demonstrated.

A Note on the Resistance of Bodies of Revolution and Ship Forms

1974 ◽  
Vol 18 (03) ◽  
pp. 153-168
Author(s):  
N. Matheson ◽  
P. N. Joubert
Keyword(s):  
Boundary Layer ◽  
Reasonable Agreement ◽  
The Body ◽  
Experimental Results ◽  
Body Of Revolution ◽  
Bodies Of Revolution ◽  
Boundary Layer Development ◽  
Layer Development

A simple so-called 'equivalent' body of revolution is proposed for reflex ship forms in an attempt to simplify calculation of the boundary layer over a ship's hull when there is no wavemaking. How­ever, exhaustive testing of one body of revolution did not produce a favorable comparison with re­sults for the corresponding reflex model. Gadd's recently proposed theory was used to calculate the boundary-layer development over the body of revolution. Reasonable agreement was obtained between the calculated and experimental results.

Flow Interaction Near the Tail of a Body of Revolution—Part 1: Flow Exterior to Boundary Layer and Wake

1976 ◽  
Vol 98 (3) ◽  
pp. 531-537 ◽  
Author(s):  
A. Nakayama ◽  
V. C. Patel ◽  
L. Landweber
Keyword(s):  
Boundary Layer ◽  
Integral Equation ◽  
Potential Flow ◽  
Present Method ◽  
Iterative Procedure ◽  
The Body ◽  
Body Of Revolution ◽  
Near Wake ◽  
Momentum Integral ◽  
Good Agreement

An iterative procedure for the calculation of the thick attached turbulent boundary layer near the tail of a body of revolution is presented. The procedure consists of the potential-flow calculation by a method of integral equation of the first kind and the calculation of the development of the boundary layer and the wake using an integral method with the condition that the velocity remains continuous across the edge of the boundary layer and the wake. The additional terms that appear in the momentum integral equation for the thick boundary layer and the near wake are taken into account and the pressure difference between the body surface and the edge of the boundary layer and the wake can be determined. The results obtained by the present method are in good agreement with the experimental data. Part 1 of this paper deals with the potential flow, while Part 2 [1] describes the boundary layer and wake calculations, and the overall iterative procedure and results.

Survey on the Indirect Methods of Potential Flow Used for the Optimization of Airships Profile

2014 ◽  
Vol 554 ◽  
pp. 717-723
Author(s):  
Reza Abbasabadi Hassanzadeh ◽  
Shahab Shariatmadari ◽  
Ali Chegeni ◽  
Seyed Alireza Ghazanfari ◽  
Mahdi Nakisa
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Flow Field ◽  
Drag Coefficient ◽  
Body Surface ◽  
Potential Flow ◽  
The Body ◽  
Indirect Methods ◽  
Singularity Method ◽  
Singularity Distribution

The present study aims to investigate the optimized profile of the body through minimizing the Drag coefficient in certain Reynolds regime. For this purpose, effective aerodynamic computations are required to find the Drag coefficient. Then, the computations should be coupled thorough an optimization process to obtain the optimized profile. The aerodynamic computations include calculating the surrounding potential flow field of an object, calculating the laminar and turbulent boundary layer close to the object, and calculating the Drag coefficient of the object’s body surface. To optimize the profile, indirect methods are used to calculate the potential flow since the object profile is initially amorphous. In addition to the indirect methods, the present study has also used axial singularity method which is more precise and efficient compared to other methods. In this method, the body profile is not optimized directly. Instead, a sink-and-source singularity distribution is used on the axis to model the body profile and calculate the relevant viscose flow field.

Potential and Viscous Parts of the Thrust Deduction and Wake Fraction for an Ellipsoid of Revolution

1960 ◽  
Vol 4 (03) ◽  
pp. 1-16
Author(s):  
Stavros Tsakonas ◽  
Winnifred R. Jacobs
Keyword(s):  
Boundary Layer ◽  
Potential Flow ◽  
Functional Dependence ◽  
Longitudinal Axis ◽  
Layer Growth ◽  
The Body ◽  
Displacement Thickness ◽  
Layer Effect ◽  
Ellipsoid Of Revolution ◽  
Equivalent Sources

Expressions are developed for wake fraction and thrust deduction due to the potential flow and to the boundary-layer effects for a fully-submerged prolate ellipsoid of revolution. The functional dependence of wake fraction and thrust deduction on axial-propeller clearance, body slenderness, after body geometry, and Reynolds number (scale effect) are exhibited for both potential and viscous-flow cases. Closed-form expressions are derived for the potential-flow case by representing the body by a line source-sink distribution and the propeller action by a sink disk. The boundary-layer effect is determined by Lighthill's method of equivalent sources distributed on the surface having strength proportional to the displacement thickness and its derivative. The wake is replaced by a cylinder of diameter equal to twice the displacement thickness at the stern. Although in practice the propeller is usually fully submerged in the wake of the hull, in this case the substitute cylinder has been shown by computation to be no wider than the hub diameter and thus the propeller is operating in a potential field. This consideration is fundamental to the construction of a possible mathematical model having the surface sources mentioned and an equivalent sink on the longitudinal axis whose position is determined on the basis of the velocity distribution in the wake. Computational work is carried out for a modification of the airship Akron. Four different methods, with various degrees of accuracy, are used for the evaluation of the boundary-layer growth in order to ascertain the degree of sensitivity of the thrust deduction and wake fraction to the boundary-layer development.

Laminar-To-Turbulent Transition on a Body of Revolution With an Extended Favorable Pressure Gradient Forebody

1984 ◽  
Vol 106 (2) ◽  
pp. 202-210 ◽  
Author(s):  
R. J. Hansen ◽  
J. G. Hoyt
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
The Body ◽  
Boundary Layer Transition ◽  
Single Element ◽  
Body Of Revolution ◽  
Laminar To Turbulent Transition ◽  
Turbulent Transition ◽  
Roughness Elements ◽  
Favorable Pressure Gradient

An experimental study of the laminar-to-turbulent transition and resulting hydrodynamic forces on a body of revolution with a long, favorable pressure gradient forebody (i.e., where pressure is dropping and the flow accelerating) is reported. Over a substantial range of body velocity and angle of attack the favorable pressure gradient is shown to postpone transition to the point of laminar separation, and this extended laminar region results in a much lower hydrodynamic drag than is characteristic of an all-turbulent body. The intermittency of the boundary layer and the propagation characteristics of turbulent spots in the extended favorable pressure gradient region are quantified by hot film probes mounted flush with the body surface. The sensitivity of the boundary layer transition to three-dimensional surface roughness elements located in tandem (along a streamline) is also quantified. A number of such elements in tandem causes transition at a lower Reynolds number than would a single element of the same size, this effect becoming more pronounced with increasing number of roughness elements and decreasing space between them.

Large-eddy simulation of flow over an axisymmetric body of revolution

2018 ◽  
Vol 853 ◽  
pp. 537-563 ◽  
Author(s):  
Praveen Kumar ◽  
Krishnan Mahesh
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Large Eddy Simulation ◽  
Axisymmetric Body ◽  
The Body ◽  
Computational Domain ◽  
Body Of Revolution ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Self Similar

Wall-resolved large-eddy simulation (LES) is used to simulate flow over an axisymmetric body of revolution at a Reynolds number, $Re=1.1\times 10^{6}$, based on the free-stream velocity and the length of the body. The geometry used in the present work is an idealized submarine hull (DARPA SUBOFF without appendages) at zero angle of pitch and yaw. The computational domain is chosen to avoid confinement effects and capture the wake up to fifteen diameters downstream of the body. The unstructured computational grid is designed to capture the fine near-wall flow structures as well as the wake evolution. LES results show good agreement with the available experimental data. The axisymmetric turbulent boundary layer has higher skin friction and higher radial decay of turbulence away from the wall, compared to a planar turbulent boundary layer under similar conditions. The mean streamwise velocity exhibits self-similarity, but the turbulent intensities are not self-similar over the length of the simulated wake, consistent with previous studies reported in the literature. The axisymmetric wake shifts from high-$Re$ to low-$Re$ equilibrium self-similar solutions, which were only observed for axisymmetric wakes of bluff bodies in the past.

scholarly journals Analysis of the axisymmetrical ionized gas boundary layer adjacent to porous contour of the body of revolution

2016 ◽  
Vol 20 (2) ◽  
pp. 529-540
Author(s):  
Slobodan Savic ◽  
Branko Obrovic ◽  
Nebojsa Hristov
Keyword(s):  
Boundary Layer ◽  
Gas Flow ◽  
Mhd Flow ◽  
The Body ◽  
Generalized Solutions ◽  
Body Of Revolution ◽  
Ionized Gas ◽  
Bodies Of Revolution ◽  
Boundary Layer Equations ◽  
Longitudinal Coordinate

The ionized gas flow in the boundary layer on bodies of revolution with porous contour is studied in this paper. The gas electroconductivity is assumed to be a function of the longitudinal coordinate x. The problem is solved using Saljnikov's version of the general similarity method. This paper is an extension of Saljnikov?s generalized solutions and their application to a particular case of magnetohydrodynamic (MHD) flow. Generalized boundary layer equations have been numerically solved in a four-parametric localized approximation and characteristics of some physical quantities in the boundary layer has been studied.

Uniform asymptotic solutions for potential flow about a slender body of revolution

1975 ◽  
Vol 67 (4) ◽  
pp. 817-827 ◽  
Author(s):  
James Geer
Keyword(s):  
Potential Flow ◽  
The Body ◽  
Slender Body ◽  
Linear Integral Equation ◽  
Body Of Revolution ◽  
Uniform Asymptotic Expansion ◽  
Arbitrary Potential ◽  
Linear Integral ◽  
Special Case ◽  
Slender Body Of Revolution

The general problem of potential flow past a slender body of revolution is considered. The flow incident on the body is described by an arbitrary potential function and hence the results presented here extend those obtained by Handels-man & Keller (1967 α). The part of the potential due to the presence of the body is represented as a superposition of potentials due to point singularities (sources, dipoles and higher-order singularities) distributed along a segment of the axis of the body inside the body. The boundary condition on the body leads to a linear integral equation for the density of the singularities. The complete uniform asymptotic expansion of the solution of this equation, as well as the extent of the distribution, is obtained using the method of Handelsman & Keller. The special case of transverse incident flow is considered in detail. Complete expansions for the dipole moment of the distribution and the virtual mass of the body are obtained. Some general comments on the method of Handelsman & Keller are given, and may be useful to others wishing to use their method.

scholarly journals A study on the size of snow particles in powder-snow avalanches

2001 ◽  
Vol 32 ◽  
pp. 259-262 ◽  
Author(s):  
Marie Clément-Rastello
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
The Body ◽  
Snow Avalanche ◽  
Snow Avalanches ◽  
Typical Size ◽  
Size Of Particles

AbstractIn this work, we study the size of the particles involved in a powder-snow avalanche. To determine this value, we study all the phenomena encountered by the particles before they arrive in the “body” of the avalanche. We study the boundary layer which is at the bottom of the avalanche. We determine, with the help of experimental data, the range of sizes of particles that can be entrained by the avalanche. We then examine the possibility of these particles reaching the top of the boundary layer and thus taking part in the avalanche. Our final result is that the typical size of particles suspended in a powder-snow avalanche is < 200 μm.

A wake source model for bluff body potential flow

1970 ◽  
Vol 40 (3) ◽  
pp. 577-594 ◽  
Author(s):  
G. V. Parkinson ◽  
T. Jandali
Keyword(s):  
Experimental Data ◽  
Pressure Distribution ◽  
Critical Points ◽  
Potential Flow ◽  
Bluff Body ◽  
Pressure Coefficient ◽  
Present Theory ◽  
Source Model ◽  
The Body ◽  
Body Potential

A theory is presented for two-dimensional incompressible potential flow external to a symmetrical bluff body and its wake. The desired flow-separation points are made the critical points of a conformal transformation to a complex plane in which surface sources in the wake create stagnation conditions at the critical points. The stagnation streamlines then transform to tangential separation streamlines in the physical plane, with separation at the desired pressure. The position and strength of the sources are determined by the requirements of separation position and pressure coefficient. The flow inside the separation streamlines is ignored and base pressure is assumed constant at the separation value. Features of the theoretical model include a finite wake width, a pressure distribution on the separation streamlines decreasing asymptotically towards the free stream value at infinity and a simple analytic expression for the pressure distribution on the body. Comparisons of the theory with experimental data and with other theories are presented for the normal plate, the circular cylinder, the 90° wedge, and the elliptical cylinder. Although simpler to apply than the other theories, the present theory produces at least as good agreement with the experimental data.

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