scholarly journals RESEARCH AND MODELING OF FLUID MOTION IN THE CASE WHEN THE VOLUME OF THE FLUID DOES NOT CHANGE AND IN THE CASE WHEN THE VOLUME CHANGES

2020 ◽  
Vol 70 (2) ◽  
pp. 149-154
Author(s):  
S.A. Abdymanapov ◽  
◽  
L.G. Kassenova ◽  
Keyword(s):  
Mathematical Model ◽  
Incompressible Fluid ◽  
Incompressible Liquid ◽  
Continuous Medium ◽  
Fluid Motion ◽  
Volume Changes ◽  
Friction Forces ◽  
Tangential Forces ◽  
Pressure Changes ◽  
Compression Resistance

A liquid is a physical body that has the property of fluidity, so it does not have its own shape and takes the form of a vessel that it fills. Liquids are divided into two types: drip and gaseous. Droplet liquids are characterized by high compression resistance (almost complete incompressibility) and low resistance to tensile and tangential forces, due to the insignificance of the coupling forces and friction forces between the liquid particles. An incompressible fluid is a mathematical model of a continuous medium whose density is preserved when the pressure changes. When defining an incompressible liquid, it is assumed that it retains the basic properties of the liquid, in particular, to change shape at a constant volume. The article presents the experiments demonstrating two types of incompressible fluid are presented. The first type is the motion of fluid not changing its volume due to elastic deformation. The second type is the formation of vortices during the expansion of the fluid that has received additional kinetic energy. Formulas for calculating and modeling vortices are proposed.

Pressure Changes Induced by Whole Body Acceleration Shocks

1991 ◽  
Vol 113 (1) ◽  
pp. 27-29 ◽  
Author(s):  
E. Belardinelli ◽  
M. Ursino ◽  
G. Fabbri ◽  
A. Cevese ◽  
F. Schena
Keyword(s):  
Mathematical Model ◽  
Carotid Artery ◽  
Normal Pressure ◽  
Compressed Air ◽  
Whole Body ◽  
Body Acceleration ◽  
Vascular Bed ◽  
Pressure Changes ◽  
The Mathematical Model

In the present paper pressure changes induced by sudden body acceleration are studied “in vivo” on the dog and compared to the results obtainable with a recently developed mathematical model. A dog was fixed to a movable table, which was accelerated by a compressed air piston for less than 1 s. Acceleration was varied by changing the air pressure in the piston. Pressure was measured during the experiment at different points along the vascular bed. However, only data obtained in the carotid artery and abdominal aorta are presented here. The results demonstrated that impulse body accelerations cause significant pressure peaks in the vessel examined (about + 25 mmHg in the carotid artery with body acceleration of g/2). Moreover, pressure changes are rapidly damped, with a time constant of about 0.1s. From the present results it may be concluded that, according to the prediction of the mathematical model, body accelerations such as those occurring in normal life can induce pressure changes well beyond the normal pressure value.

scholarly journals A MATHEMATICAL MODEL OF NONSTATIONARY MOTION OF A VISCOELASTIC FLUID IN ROLLER BEARINGS

2019 ◽  
Vol 81 (4) ◽  
pp. 501-512
Author(s):  
I.A. Zhurba Eremeeva ◽  
D. Scerrato ◽  
C. Cardillo ◽  
A. Tran
Keyword(s):  
Mathematical Model ◽  
Viscoelastic Fluid ◽  
Viscoelastic Properties ◽  
Fluid Model ◽  
Maxwell Fluid ◽  
Initial Boundary ◽  
Deborah Number ◽  
Nonstationary Motion ◽  
Friction Forces ◽  
Roller Bearings

Nowadays, the emergence of new lubricants requires an enhancement of the rheological models and methods used for solution of corresponding initial boundary-value problems. In particular, models that take into account viscoelastic properties are of great interest. In the present paper we consider the mathematical model of nonstationary motion of a viscoelastic fluid in roller bearings. We used the Maxwell fluid model for the modeling of fluid properties. The viscoelastic properties are exhibited by many lubricants that use polymer additives. In addition, viscoelastic properties can be essential at high fluid speeds. Also, viscoelastic properties can be significant in the case of thin gaps. Maxwell's model is one of the most common models of viscoelastic materials. It combines the relative simplicity of constitutive equations with the ability to describe a stress relaxation. In addition, viscoelastic fluids also allow us to describe some effects that are missing in the case of viscous fluid. An example it is worth to mention the Weissenberg effect and a number of others. In particular, such effects can be used to increase the efficiency of the film carrier in the sliding bearings. Here we introduced characteristic assumptions on the form of the flow, allowing to significantly simplify the solution of the problem. We consider so-called self-similar solutions, which allows us to get a solution in an analytical form. As a result these assumptions, the formulae for pressure and friction forces are derived. Their dependency on time and Deborah number is analyzed. The limiting values of the flow characteristics were obtained. The latter can be used for steady state of the flow regime. Differences from the case of Newtonian fluid are discussed. It is shown that viscoelastic properties are most evident at the initial stage of flow, when the effects of non-stationarity are most important.

On the correctness of a phenomenological model of equilibrium phase transitions in a deformable elastic medium

1992 ◽  
Vol 3 (2) ◽  
pp. 181-191
Author(s):  
A. M. Meirmanov ◽  
N. V. Shemetov
Keyword(s):  
Mathematical Model ◽  
Continuous Medium ◽  
Equilibrium Phase ◽  
Elastic Solid ◽  
Complementary Energy ◽  
Structure Of Solutions ◽  
Two Phase ◽  
Pure Phase ◽  
The Mathematical Model ◽  
Uniqueness Of A Solution

In this paper we investigate the mathematical model of the equilibrium of a finite volume in ℝn (n = 1,2, 3) of a two-phase continuous medium, under the assumption that each pure phase is an isotropic elastic solid. The main results in this paper are:(i) the existence and uniqueness of a solution of this mathematical model;(ii) a discussion of the stress-strain law associated with the free energy of this two-phase continuous medium, which is multiple-valued due to the non-smoothness of the Gibbs potential (complementary energy);(iii) a description of the structure of solutions in plane strain.

Changes in intestinal volume with hemorrhage

1960 ◽  
Vol 199 (3) ◽  
pp. 589-592 ◽  
Author(s):  
Paul C. Johnson
Keyword(s):  
Small Intestine ◽  
Blood Volume ◽  
Sympathetic Nerve Activity ◽  
Venous Pressure ◽  
Volume Changes ◽  
Local Pressure ◽  
Local Reduction ◽  
Pressure Changes ◽  
Sympathetic Discharge ◽  
Intestinal Weight

The purpose of these experiments was to study the changes in intestinal volume occurring with hemorrhage, utilizing a gravimetric technique which permitted a study of small segments of the intestine. It had been observed previously that intestinal weight often increased in the upper small intestine during hemorrhage, while in the lower small intestine it usually decreased. In studying the latter effect it was found that sympathetic nerve activity and reduction of venous pressure were both important in decreasing intestinal volume. Changes in tonus and local reduction in arterial pressure did not appear to be important. The increase in volume with hemorrhage appeared due to epinephrine discharge from the adrenal medulla since it was eliminated by adrenalectomy. Local pressure changes and alteration of tonus were eliminated as causal factors. It appears that systemic hypotension induces sympathetic discharge which in turn may cause either an increase or a decrease in intestinal blood volume. Sympathetic discharge over the vasoconstrictor fibers reduces blood volume while adrenal medullary secretion increases it. The observed response is apparently a resultant of these two antagonistic effects.

Effective Linear Friction Welding Machine Redesign through Process Analysis

2014 ◽  
Vol 622-623 ◽  
pp. 484-491
Author(s):  
Gianluca Buffa ◽  
Marco Cammalleri ◽  
Davide Campanella ◽  
Livan Fratini ◽  
Achilles Vairis
Keyword(s):  
Friction Welding ◽  
High Frequency ◽  
Process Analysis ◽  
High Frequency Oscillation ◽  
Linear Friction Welding ◽  
Friction Forces ◽  
Linear Friction ◽  
Tangential Forces ◽  
Process Measurements ◽  
Solid State Joining

Linear friction welding is a solid-state joining process developed for non-axisymmetric components in which the joining of the specimens is obtained through reciprocating motion and pressure. In the process, the friction forces work due to the high frequency oscillation and the pressure between the specimens is converted in thermal energy. In order to design an effective machine, relevant issues derive from the high frequency and the large inertial forces involved in the process. In this study, the authors describe the redesign of a preexisting prototypal machine for LFW processes. A machine redesign is needed when welding high resistant materials, i.e. steels or titanium alloys, with high frequencies, up to 72 Hz. The sensors equipping the machine allows in process measurements of key process variables as temperatures of the specimens, tangential forces, accelerations and speeds. At the same time through the acquired data, the main weaknesses of the machine can be highlighted allowing for effective redesign.

Measurement of Force and Displacement for the Tribological Analysis of MEMS

2005 ◽  
Author(s):  
Joshua S. Wiehn ◽  
Michael T. Dugger ◽  
Thomas E. Buchheit
Keyword(s):  
Friction And Wear ◽  
Microelectromechanical Systems ◽  
Mems Devices ◽  
Force Output ◽  
Electrostatic Actuators ◽  
Friction Forces ◽  
Tangential Forces ◽  
Tribological Analysis ◽  
Output Characteristics ◽  
Force Calibration

The tribological interfaces in microelectromechanical systems (MEMS) pose a significant hurdle in the advancement of MEMS. In order to gain a better understanding of these tribological interfaces, meaningful friction and wear measurements of MEMS devices must be made at loads and speeds relevant to MEMS operation. Devices containing isolated tribological contacts from which quantitative friction forces can be extracted have been developed. Since independent in-plane measurement of forces are not available for structures that are on the order of microns thick, the normal and tangential forces between structures are typically estimated based on the calculation of the force output of electrostatic actuators, and the force required to bend compliant suspensions. We will discuss the uncertainties associated with the measurement of applied and friction forces in MEMS tribometers, and metrology needs for improved tribological analysis of dynamic microsystems. We will also present a method of independent force calibration in these devices, and compare measured output characteristics with those predicted from mechanics and electrostatics.

Effect of sinusoidal forcing of ventilatory volume on avian breathing frequency

1985 ◽  
Vol 59 (3) ◽  
pp. 991-1000 ◽  
Author(s):  
G. O. Ballam ◽  
T. L. Clanton ◽  
R. P. Kaminski ◽  
A. L. Kunz
Keyword(s):  
Pressure Transducer ◽  
Threshold Model ◽  
Constant Flow ◽  
Breathing Frequency ◽  
Volume Changes ◽  
Passive Pressure ◽  
Beat Pattern ◽  
Force Volume ◽  
Pressure Changes ◽  
Ventilatory Volume

Awake chickens were unidirectionally ventilated at 3.6 l . min-1 with 3.2–4.8% CO2 in air. The air sacs on each side were made confluent and implanted with exit tubes connected to the following three devices: 1) a system of constant-flow generators which remove air at exactly the same rate that it entered the trachea, allowing no port for spontaneous volume changes; 2) a sinusoidal pump to force volume changes in the chicken; and 3) a pressure transducer to record air sac pressure, which reflected the sum of two pressure components, the passive pressure changes created by the pump and the active pressure changes due to breathing efforts. Over a range of pump frequencies, the amplitude of measured air sac pressure changes varied inversely with frequency. Above and below this range, pressure showed a beat pattern, indicating a difference in the frequencies of the two pressure components. Within the range lacking a beat pattern, breathing movements and the pump stroke had the same frequency. This range was greater at increased stroke volume. Breathing efforts worked with the pump at the high end of the range and against the pump at the low end. These findings show further evidence of the presence of a response to volume forcing and fit a previously described volume threshold model.

On the Approximated Expression of the Axial Perturbation Velocities in the Actuator Disc Theory

1967 ◽  
Vol 71 (683) ◽  
pp. 799-800
Author(s):  
G. Bussi
Keyword(s):  
Mathematical Model ◽  
Equilibrium Solution ◽  
Velocity Potential ◽  
Equations Of Motion ◽  
Fluid Motion ◽  
Real Problem ◽  
Complex Flow ◽  
Perturbation Velocity ◽  
Actuator Disc ◽  
Radial Equilibrium

Fluid motion in an annulus is described, in the absence of radial velocity, by the simple radial equilibrium equation. This equation is used to describe the flow in an axial turbomachine some distance ahead and behind the rows of blades, where radial displacements have already decayed.In the neighbourhood of and between the blades the fluid motion is far more complex than the flow in the radial equilibrium condition. Most of the difficulties of the real problem can be overcome by introducing the actuator disc mathematical model. The actuator disc divides the complex flow field into two simpler fields, each free from blades, i.e. a simple annulus. The equations of motion in each field are easily linearised by posing some particular restrictions concerning the velocity profiles and by conceiving the velocity as the sum of the radial equilibrium solution and of small perturbed quantities. These are radial and axial perturbation velocities vanishing far from the actuator disc, and are given by a perturbation velocity potential.

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