Year: 1984 Language: english Author: J .A. Sparenberg Genre: Textbook Format: PDF Quality: eBook Pages count: 293 Description: This is a treatment of a number of aspects of the theory of hydrodynamic propulsion. It has been written with in mind technical propulsion systems generally based on lift producing profiles. We assume the fluid, which is admitted in conventional hydrodynamics, to be incompressible. Further we assume the occurring Reynolds numbers to be sufficiently high such that the inertia forces dominate by far the viscous forces, therefore we take the fluid to be inviscid. Of course it must be realized that viscosity plays an important part in a number of phenomena displayed in real flows, such as flow separation at the nose of a profile and the entrainment of fluid by a ship's hull. Another approximation which will be used in general is that the problems are linearized. In other words it is assumed that the induced disturbance velocities are sufficiently small, such that their squares can be neglected with respect to these velocities themselves. Hence it is necessary to evaluate the domain of validity of the results with respect to these two a priori assumptions. Anyhow it seems advisable to have first a good understanding of the linearized non-viscous theory before embarking on complicated theories which describe more or less realistic situations. For elaborations of the theory to realistic situations we will refer to current literature. In low Reynolds number flow, singular external forces and moments are very useful. It is one of the objectives of this book to promote the use of external force fields also in the case of incompressible and inviscid fluids as an expedient to generate velocity fields. Although in most text books external force fields appear in the equations of motion, usually it is assumed that they have an impulsive character or that they are the gradient of a potential function. In the latter case they have lost, in relation to incompressible fluids the ability of inducing velocities, they only change the pressure field. An interesting feature of non conservative external force fields is that they can generate vorticity in an inviscid fluid. By this we have no need in a discussion about the origin of vorticity, to make use of a slight viscosity which afterwards is abandoned again. Using external force fields the concepts of for instance pressure dipole and actuator disk, arise in a natural way from the integration of the equations of motion.
Вы не можете начинать темы Вы не можете отвечать на сообщения Вы не можете редактировать свои сообщения Вы не можете удалять свои сообщения Вы не можете голосовать в опросах Вы не можете прикреплять файлы к сообщениям Вы не можете скачивать файлы
Elements of hydrodynamic propulsion
Language: english
Author: J .A. Sparenberg
Genre: Textbook
Format: PDF
Quality: eBook
Pages count: 293
Description: This is a treatment of a number of aspects of the theory of hydrodynamic
propulsion. It has been written with in mind technical propulsion
systems generally based on lift producing profiles.
We assume the fluid, which is admitted in conventional hydrodynamics,
to be incompressible. Further we assume the occurring Reynolds
numbers to be sufficiently high such that the inertia forces dominate by
far the viscous forces, therefore we take the fluid to be inviscid. Of course
it must be realized that viscosity plays an important part in a number of
phenomena displayed in real flows, such as flow separation at the nose of
a profile and the entrainment of fluid by a ship's hull. Another approximation
which will be used in general is that the problems are
linearized. In other words it is assumed that the induced disturbance
velocities are sufficiently small, such that their squares can be neglected
with respect to these velocities themselves. Hence it is necessary to
evaluate the domain of validity of the results with respect to these two a
priori assumptions. Anyhow it seems advisable to have first a good
understanding of the linearized non-viscous theory before embarking on
complicated theories which describe more or less realistic situations. For
elaborations of the theory to realistic situations we will refer to current
literature.
In low Reynolds number flow, singular external forces and moments
are very useful. It is one of the objectives of this book to promote the use
of external force fields also in the case of incompressible and inviscid
fluids as an expedient to generate velocity fields. Although in most text
books external force fields appear in the equations of motion, usually it is
assumed that they have an impulsive character or that they are the
gradient of a potential function. In the latter case they have lost, in
relation to incompressible fluids the ability of inducing velocities, they
only change the pressure field. An interesting feature of non conservative
external force fields is that they can generate vorticity in an inviscid fluid.
By this we have no need in a discussion about the origin of vorticity, to
make use of a slight viscosity which afterwards is abandoned again.
Using external force fields the concepts of for instance pressure dipole
and actuator disk, arise in a natural way from the integration of the
equations of motion.
Contents
Screenshots
Elements of hydrodynamic propulsion.pdf
Скачать [7 KB]
Поделиться