Jacob Kazakia

Lehigh University · Department of Mechanical Engineering and Mechanics

Practicing Mechanical engineers desire to advance their careers and job satisfaction by pursuing distance graduate degree programs, mainly towards Master’s degrees. The start up stage of such studies is problematic among engineers who stayed away from formal education for a period of years. The structure of the Graduate Program in Mechanical Engine...

Pressure measurements in flows of highly viscous and elastic fluids are of practical importance in many manufacturing processes. Problems may arise during such pressure measurements, since high fluid viscosity and elasticity result in excessive dynamic response time of the pressure measuring systems as well as in some distortion. This is true for s...

Labyrinth seals are commonly found in turbines and compressors. Their objective is to control gas leakage from high pressure regions to low pressure regions. The correct prediction and control of this leakage is crucial for the efficient and economic operation of turbomachinery. In this paper we present approaches for obtaining the above prediction...

Labyrinth seals are commonly found in turbines and compressors. Their objective is to control gas leakage from high pressure regions to low pressure regions. The correct prediction and control of this leakage is crucial for the efficient and economic operation of turbomachinery. In this paper we present approaches for obtaining the above prediction...

Pressure measurements in flows of highly viscous and elastic fluids are of practical importance in polymer processing and rheology systems. Special problems arise during such pressure measurements. High fluid viscosity results in excessive dynamic response time (rise time) of the pressure measuring systems. This is true for systems that consist of...

An asymptotic analysis of the equations describing supersonic turbulent flow over an adiabatic wall is carried out for high Reynolds numbers, Re, and mainstream Mach numbers, M e=O(1). A general expression for the adiabatic-wall temperature is derived. The asymptotic theory constrains the types of turbulence models that are suitable to represent th...

The leakage flow rate through a sequence of labyrinth seal cavities, and the associated pressure and the circumferential velocity distributions are calculated for seals used in turbomachinery. Computational Fluid Dynamics is used to justify the use of bulk cavity variables, and to analyze the details of the flow in a single cavity under steady stat...

An asymptotic analysis of the compressible turbulent boundary-layer equations is carried out for large Reynolds numbers and mainstream Mach numbers of O(1). A self-consistent two-layer asymptotic structure is described wherein the time-mean velocity and total enthalpy are logarithmic within the overlap zone but in terms of the Howarth–Dorodnitsyn v...

With increasing mainstream Mach number, viscous dissipation becomes a progressively important influence in high-speed compressible turbulent boundary layers. An asymptotic analysis is carried out for high Reynolds numbers and Mach numbers of order 1, and it is shown that viscous dissipation gives rise to important terms in the solution of the total...

The development of embedded functions to represent the mean velocity and total enthalpy distributions in the wall layer of a supersonic turbulent boundary layer is considered. The asymptotic scaling laws (in the limit of large Reynolds number) for high speed compressible flows are obtained to facilitate eventual implementation of the embedded funct...

We describe an algorithm for the determination of a sequence of n orthogonal transformations which transform a n × n, trace free, real symmetric matrix into a matrix whose diagonal elements are all zero. Explicit results for the 3 × 3 case are given.

The use of controlled sound, generated by unidirectional secondary sources, in cancelling primary noise of low frequency in long ducts is investigated. It is shown that for broadband primary noise, say four octaves, the simple arrangement of two secondary speakers used in many experimental studies is not efficient. This inefficiency manifests itsel...

The transfer mechanism of momentum from the boundaries into the interior of a viscoelastic fluid is examined in the case when the boundary consists of two parallel plates.Special emphasis is given to the case of a Maxwellian fluid. It is seen that an increase in the azimuthal angular velocity at the boundaries progresses into the interior of the li...

Results obtained in previous papers on the flow of an incompressible non-Newtonian fluid, satisfying the second-order Rivlin—Ericksen constitutive equation, in the annular region between infinite circular cylinders with parallel axes, which results from the longitudinal steady motion of the inner cylinder, or the existence of a longitudinal pressur...

An incompressible viscoelastic fluid is contained between parallel rigid plates which at some instant of time are subjected to a translational velocity which is then held constant. The dependence on time of the resulting flow field in the fluid is calculated. Similar calculations are carried out when the fluid is contained in an infinitely long cir...

The effect is discussed of a superposed longitudinal sinusoidal vibration on the flow, under a constant pressure gradient, of a slightly non-Newtonian fluid in a straight pipe of non-circular cross-section. It is found that a flow in transverse planes is produced. This is the superposition of steady and sinusoidal flows. The stream-function corresp...

Summary An incompressible, isotropic, non-Newtonian fluid undergoes plane Poiseuille flow between two parallel plates, or through a pipe of circular cross-section, as a result of a uniform time-independent pressure gradient. The effect is studied of superposed vibrations of the boundaries, which are not necessarily purely sinusoidal, on the mean ra...

It has been noted (see, for example, [1]) that in turbulent flow of a Newtonian fluid in a straight pipe with circular cross-section, under a constant pressure gradient, the rate of discharge is not proportional to the pressure gradient as it is for laminar flow. Also, the distribution of the time-averaged velocity over a cross-section of the tube...

It has been observed by Mena 1) that when a polymer solution flows through a tube of circular cross-section under a constant pressure gradient, the rate of discharge is increased if the tube is subjected to a longitudinal sinusoidal vibration. It is shown in the present paper how this effect can be predicted on the basis of two different assumption...

This study discusses the evolution of long gravity waves on shear flows. Although the paper is concerned mainly with finite amplitude neutrally stable flows which contain a critical level, a new representation is given for the unstable mode solutions of the linearized equations. From these solutions it appears that focusing instabilities, usually a...

Results obtained in a previous paper byBallal andRivlin on the forces associated with the slow flow of an incompressible non-Newtonian fluid, contained in the annular region between two infinite eccentric rotating cylinders, are applied to the calculation of the forces associated with the planetary motion of the inner cylinder about the axis of the...

Theorems are derived, within the framework of the second-order Rivlin-Ericksen theory, relating to the superposition of longitudinal flows on plane flows in an incompressible isotropic viscoelastic fluid. Also, some theorems are obtained concerning the effects of inertia on the solution of plane flow problems in such viscoelastic fluids.

In a previous paper, Ballal and Rivlin (1) have considered the steady flow in a mass of incompressible viscoelastic fluid, contained in the annular region between two circular cylinders with parallel axes, which results from the rotation with constant angular velocities of one or both of the cylinders about their respective axes. The flow was assum...

The early phases of propagation of a large amplitude electromagnetic disturbance in a nonlinear dielectric slab embedded between two linear media are investigated by the method of characteristics. This disturbance is triggered by the arrival of an electromagnetic shock wave at one of the interfaces. Reflection and transmission of an arbitrary signa...

This paper continues the investigation of large amplitude waves in bounded media started by Cekirge & Varley (1973). It describes the early stages of the deformation produced in an elastic slab contained between two parallel, plane interfaces when the normal traction at one of them changes discontinuously. During the subsequent deformation energy i...

Representations are derived that describe the interactions of the waves that are reflected from both perfectly rigid and perfectly free interfaces during the arrival of a centred wave with any wave travelling in the opposite direction. These are used to analyse the early stages of the deformation produced when the traction at the loaded boundary co...