Experimental Studies of Supersonic Steam Flow in the Flat Nozzle Blade Cascade at Different Initial Steam Conditions

2014 ◽  
Author(s):  
Vladimir Gribin ◽  
Aleksandr Tishchenko ◽  
Ilya Gavrilov ◽  
Victor Tishchenko ◽  
Sergey Khomyakov ◽  
...  
Keyword(s):  
Shock Waves ◽  
Visual Information ◽  
Initial Conditions ◽  
Experimental Studies ◽  
Steam Flow ◽  
Wave System ◽  
Frequency Spectra ◽  
Blade Cascade ◽  
Object Of Study ◽  
Nozzle Blade

The results of experimental studies of supersonic steam flow downstream the flat turbine nozzle blade cascade has been considered. The investigations were carried out in a broad range of steam initial conditions (superheated, dry saturated) and isentropic Mach (M1t) number downstream the object of study. The schlieren method was used to obtain the visual information about shock waves structure. The flow parameters oscillations were measured by pressure transducers situated at different locations downstream the object of study. It is shown that the occurrence of condensing shock at conditions of superheated steam upstream the nozzle blade cascade leads to the sufficient unsteadiness of shock waves system. This is due to the complex relationship between the boundary layer and a shock wave system. With changing of initial steam conditions the rearrangement of static pressure frequency spectra is observed.

Features of liquid phase movement in the inter-blade channel of nozzle blade cascade

2017 ◽  
Vol 232 (5) ◽  
pp. 452-460 ◽  
Author(s):  
Vladimir Gribin ◽  
Ilya Gavrilov ◽  
Aleksandr Tishchenko ◽  
Victor Tishchenko ◽  
Vitaliy Popov ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Laser Diagnostics ◽  
Experimental Studies ◽  
Correlation Method ◽  
Leading Edge ◽  
Steam Flow ◽  
Wet Steam ◽  
Blade Cascade ◽  
Wet Steam Flow ◽  
Nozzle Blade

The experimental results of wet steam flow in the blade channel of flat nozzle blade cascade have been considered in the paper. The aim of this work is to study the motion of liquid droplets inside the inter-blade channel. Experimental studies were performed on installation circuit of wet steam. In order to obtain velocity fields of droplets in investigated channel, the laser diagnostics system was used. It carries out the cross-correlation method—particle tracking velocimetry. Numerical simulation of wet steam flow in studied channel was performed. According to the obtained data, the main features of the droplets motion in the blade channel have been revealed. Basic droplets streams and the sources of their appearance have been determined. The process of deposition and breakdown of the droplets on the surface of the blades have been studied. It is shown that reflected region of droplets (“fountain”) is formed around the leading edge. The experimental data were compared with the results of numerical simulation of the droplets motion in the flat nozzle blade cascade.

A New View on Grasping

Motor Control ◽  
1999 ◽  
Vol 3 (3) ◽  
pp. 237-271 ◽  
Author(s):  
Jeroen B.J. Smeets ◽  
Eli Brenner
Keyword(s):  
Surface Roughness ◽  
Visual Information ◽  
Experimental Studies ◽  
Movement Speed ◽  
Object Size ◽  
Extensive Review ◽  
Minimum Jerk ◽  
Alternative Description ◽  
Position And Orientation ◽  
Shape And Size

Reaching out for an object is often described as consisting of two components that are based on different visual information. Information about the object's position and orientation guides the hand to the object, while information about the object's shape and size determines how the fingers move relative to the thumb to grasp it. We propose an alternative description, which consists of determining suitable positions on the object—on the basis of its shape, surface roughness, and so on—and then moving one's thumb and fingers more or less independently to these positions. We modeled this description using a minimum-jerk approach, whereby the finger and thumb approach their respective target positions approximately orthogonally to the surface. Our model predicts how experimental variables such as object size, movement speed, fragility, and required accuracy will influence the timing and size of the maximum aperture of the hand. An extensive review of experimental studies on grasping showed that the predicted influences correspond to human behavior.

Entrainment and growth of vortical disturbances in the channel-entrance region

2021 ◽  
Vol 927 ◽  
Author(s):  
Pierre Ricco ◽  
Claudia Alvarenga
Keyword(s):  
Initial Conditions ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Analytical Description ◽  
Reynolds Numbers ◽  
Boundary Region ◽  
Shear Layers ◽  
Base Flow ◽  
Open Boundary ◽  
Classical Stability

The entrainment of free-stream unsteady three-dimensional vortical disturbances in the entry region of a channel is studied via matched asymptotic expansions and by numerical means. The interest is in flows at Reynolds numbers where experimental studies have documented the occurrence of intense transient growth, despite the flow being stable according to classical stability analysis. The analytical description of the vortical perturbations at the channel mouth reveals how the oncoming disturbances penetrate into the wall-attached shear layers and amplify downstream. The effects of the channel confinement, the streamwise pressure gradient and the viscous/inviscid interplay between the oncoming disturbances and the boundary-layer perturbations are discussed. The composite perturbation velocity profiles are employed as initial conditions for the unsteady boundary-region perturbation equations. At a short distance from the channel mouth, the disturbance flow is mostly confined within the shear layers and assumes the form of streamwise-elongated streaks, while farther downstream the viscous disturbances permeate the whole channel although the base flow is still mostly inviscid in the core. Symmetrical disturbances exhibit a more significant growth than anti-symmetrical disturbances, the latter maintaining a nearly constant amplitude for several channel heights downstream before growing transiently, a unique feature not reported in open boundary layers. The disturbances are more intense as the frequency decreases or the bulk Reynolds number increases. We compute the spanwise wavelengths that cause the most intense downstream growth and the threshold wall-normal wavelengths below which the perturbations are damped through viscous dissipation.

Medium-Carbon Free-Cutting Steel

2019 ◽  
Vol 946 ◽  
pp. 47-52
Author(s):  
A.V. Ryabov
Keyword(s):  
Boron Nitride ◽  
Experimental Studies ◽  
Aluminium Oxide ◽  
Spherical Shape ◽  
Complex Compounds ◽  
Aluminium Nitride ◽  
Cutting Steel ◽  
Metallic Inclusions ◽  
Object Of Study ◽  
Inclusions In Steel

The paper presents theoretical and experimental studies of the formation processes of boron nitride, aluminium nitride, aluminium oxide and manganese sulphide inclusions in a free-cutting steel. Fact Sage software was used to model the behaviour of non-metallic inclusions. Formation temperatures and the amount of key inclusions in steel were calculated. Formation order of inclusions is as follows: aluminium oxide > boron nitride > manganese sulphide > aluminium nitride. The object of study was the A45AR grade steel in 1.1–1.2 kg ingots. It was melted in an induction furnace, and aluminium, nitrided ferrosilicon and ferroboron were added after deoxidation before tapping. Quality estimation included chemical composition, macro-and microstructure, the character and shape of non-metallic inclusions. The finished metal contained fine and uniformly distributed inclusions of boron nitride. Qualitative and quantitative analysis of boron nitrides distribution in metal matrix showed that they were present both as individual and complex compounds, mostly of spherical shape. The size of BN inclusions varied from 0.18 to 6.52 μm. The amount of boron added to steel did not affect the size of MnS non-metallic inclusions.

scholarly journals Physiologic blood flow is turbulent

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Khalid M. Saqr ◽  
Simon Tupin ◽  
Sherif Rashad ◽  
Toshiki Endo ◽  
Kuniyasu Niizuma ◽  
...  
Keyword(s):  
Blood Flow ◽  
Stokes Equation ◽  
Initial Conditions ◽  
Hydrodynamic Instability ◽  
Transition To Turbulence ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Frequency Spectra ◽  
Hydrodynamic Stability Theory

Abstract Contemporary paradigm of peripheral and intracranial vascular hemodynamics considers physiologic blood flow to be laminar. Transition to turbulence is considered as a driving factor for numerous diseases such as atherosclerosis, stenosis and aneurysm. Recently, turbulent flow patterns were detected in intracranial aneurysm at Reynolds number below 400 both in vitro and in silico. Blood flow is multiharmonic with considerable frequency spectra and its transition to turbulence cannot be characterized by the current transition theory of monoharmonic pulsatile flow. Thus, we decided to explore the origins of such long-standing assumption of physiologic blood flow laminarity. Here, we hypothesize that the inherited dynamics of blood flow in main arteries dictate the existence of turbulence in physiologic conditions. To illustrate our hypothesis, we have used methods and tools from chaos theory, hydrodynamic stability theory and fluid dynamics to explore the existence of turbulence in physiologic blood flow. Our investigation shows that blood flow, both as described by the Navier–Stokes equation and in vivo, exhibits three major characteristics of turbulence. Womersley’s exact solution of the Navier–Stokes equation has been used with the flow waveforms from HaeMod database, to offer reproducible evidence for our findings, as well as evidence from Doppler ultrasound measurements from healthy volunteers who are some of the authors. We evidently show that physiologic blood flow is: (1) sensitive to initial conditions, (2) in global hydrodynamic instability and (3) undergoes kinetic energy cascade of non-Kolmogorov type. We propose a novel modification of the theory of vascular hemodynamics that calls for rethinking the hemodynamic–biologic links that govern physiologic and pathologic processes.

Do the bulk solitary strain waves decay?

2008 ◽  
Vol 222 (10) ◽  
pp. 1975-1980 ◽  
Author(s):  
A M Samsonov ◽  
G V Dreiden ◽  
I V Semenova
Keyword(s):  
Shock Waves ◽  
Experimental Studies ◽  
Linear Strain ◽  
Shape Transformation ◽  
Bulk Strain ◽  
Strain Waves ◽  
Wave Guides ◽  
Short Run ◽  
Elastic Loading ◽  
Linearly Elastic Materials

Non-linearly elastic materials may provide generation of strain solitons, even under short-run and reversible (elastic) loading. Theoretical and experimental studies have been performed to prove the existence of long bulk strain solitary waves produced by a laser-induced shock wave in non-linearly elastic isotropic wave guides. Propagation of the bulk solitary density waves is studied in lengthy (over 0.5 m long) elastic wave guides, which have strong dispersion and are made of polymers with remarkable decay of any of the linear or shock waves at short distances. New experiments in lengthy bars confirm that the bulk solitons do not reveal any considerable decay and shape transformation, while linear or shock waves disappear at much shorter distance completely. Decrement values are estimated first for elastic non-linear strain waves decay in polymeric bars.

Validation of Finite Element Lower Extremity Model Using Drop Tower Testing

2013 ◽  
Author(s):  
Robbin Bertucci ◽  
R. Prabhu ◽  
M. F. Horstemeyer ◽  
James Sheng ◽  
Jun Liao ◽  
...  
Keyword(s):  
Finite Element ◽  
Shock Waves ◽  
Lower Extremity ◽  
Cause Of Death ◽  
Direct Contact ◽  
Computational Analysis ◽  
Experimental Studies ◽  
Lower Extremities ◽  
Drop Tower ◽  
Made In

Explosions are the leading cause of death on the battlefield [1]. These explosives, such as bombs and mines, generate shock waves which stimulate large accelerations and deformations. The resulting loads pose serious threats to military and civilians if not sufficiently evaluated and protected. The use of anti-vehicle landmines has become extremely common. Due to lower extremities being in direct contact with the floor of vehicles, the lower extremities are commonly injured during explosions [2]. These injuries can be seriously fatal. Although experimental studies have been performed to advance these understandings [2], limited progress has been made in computational analysis of shock waves on the lower extremity.

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