Optical Measurement and Data Reduction for Definitely Unsteady Flow Pattern

1994 ◽  
pp. 109-120
Keyword(s):  
Unsteady Flow ◽  
Flow Pattern ◽  
Data Reduction ◽  
Optical Measurement

A Note on the Estimation of Average Pressures from Instantaneous Velocities in Unsteady Flow

1967 ◽  
Vol 71 (678) ◽  
pp. 440-440
Author(s):  
C. J. Wood
Keyword(s):  
Unsteady Flow ◽  
Boundary Layers ◽  
Data Reduction ◽  
Bluff Body ◽  
Wake Vortex ◽  
Two Dimensional ◽  
Experimental Check ◽  
Velocity Measurements ◽  
Periodic Disturbance ◽  
Oncoming Stream

In a recent paper, the author described some experiments in which the average base pressure on a two-dimensional bluff body was estimated from a random sample of instantaneous velocity measurements taken in the irrotational flow outside the separating boundary layers at the trailing edge. Although the oncoming stream was steady, the flow near the model was subject to a periodic disturbance emanating from the wake vortex street. An experimental check showed that the pressure estimates obtained by using the steady Bernouilli equation were reasonably accurate. This note points out that the method of data reduction used in ref. 1 is not an approximation; it is exact.

560 An attempt to clarify the unsteady flow pattern and near wall stress field in the realistic cerebral aneurysm model by the PIV

2007 ◽  
Vol 2007.56 (0) ◽  
pp. 269-270
Author(s):  
Kouji Nagata ◽  
Shinichi Ito ◽  
Yasuhiko Sakai ◽  
Haruo Isoda ◽  
Takashi Kosugi ◽  
...  
Keyword(s):  
Stress Field ◽  
Unsteady Flow ◽  
Flow Pattern ◽  
Cerebral Aneurysm ◽  
Wall Stress ◽  
Aneurysm Model ◽  
Near Wall

Influence of an Adaptive Blade System on Unsteady Flow Conditions in a 2D Compressor Cascade

2017 ◽  
Author(s):  
Julija Peter ◽  
David Konstantin Tilcher ◽  
Robert Meyer ◽  
Paul Uwe Thamsen
Keyword(s):  
Phase Shift ◽  
Flow Field ◽  
Unsteady Flow ◽  
High Speed ◽  
Optical Measurement ◽  
Water Channel ◽  
Tip Clearance ◽  
Flow Conditions ◽  
Compressor Cascade ◽  
Flow Angle

The flow field inside a compressor is characterized by highly unsteady flow effects. Consequently, the performance of a compressor is significantly influenced by the complex flow field. Especially at off-design conditions, flow separation and tip clearance flow cause vortex structures and thus increased losses. The objective of this paper is to give an insight into the effect mechanism of the movable stator vanes as an adaptive system to affect unsteady flow conditions. The experiments were conducted in a stator cascade in a water channel at a Reynolds number of Re = 500 000. Inlet guide vanes with movable flaps were used to simulate the periodic variation of the inlet flow angle. As parameters, the mean stagger angle of the stator cascade as well as the phase shift between the sinusoidal movement of the stator and the inlet guide cascade were varied. By using the optical measurement technique High-Speed Particle Image Velocimetry (HS-PIV), the flow fields upstream and downstream of the stator cascade were captured. Overall, the results revealed that the loss coefficient is strongly dependent on the phase shift between the inlet guide cascade and the stator cascade. Using certain phase shifts, a reduction in losses of up to 20% was achieved by the movable stator cascade.

Study on Liquid Pipeline Water Hammer and Protective Device with Gas Concentration

2012 ◽  
Vol 616-618 ◽  
pp. 774-777 ◽  
Author(s):  
Qi Wei Yong ◽  
Ming Jiang ◽  
Yan Tang
Keyword(s):  
Unsteady Flow ◽  
Flow Pattern ◽  
Water Hammer ◽  
Sudden Increase ◽  
Protective Device ◽  
Utility Model ◽  
Gas Concentration ◽  
Cavity Collapse ◽  
New Type ◽  
National Patent

When pressure is low enough in pipeline the transported liquid vaporizes, and air can be let into the pipeline for various of reasons. After the pipeline is shut down, the air/vapor will gather and cavitation occurs. The existence of cavity in liquid pipeline is harmful when restarting the pipeline because the downstream equipments may not work properly. When the cavity collapse, the unsteady flow pattern in pipeline may be intensified due to the sudden increase of pressure and temperature, which may cause serious accidents. Analysis and calculation for the hydraulic status in gas concentrated liquid pipeline are presented in this paper using the rigid liquid column theory. A new type of protective device which automatically let in and release gas is designed by the author. The device is awarded the national patent of utility model.

scholarly journals Role of Acoustic Streaming in Formation of Unsteady Flow in Billet Sump during Ultrasonic DC Casting of Aluminum Alloys

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3532 ◽  
Author(s):  
Sergey Komarov ◽  
Takuya Yamamoto
Keyword(s):  
Temperature Distribution ◽  
Unsteady Flow ◽  
Mushy Zone ◽  
Flow Pattern ◽  
Acoustic Streaming ◽  
Ultrasound Irradiation ◽  
Numerical Code ◽  
Melt Flow ◽  
Hot Top ◽  
Dc Casting

The present work investigated melt flow pattern and temperature distribution in the sump of aluminum billets produced in a hot-top equipped direct chilling (DC) caster conventionally and with ultrasonic irradiation. The main emphasis was placed on clarifying the effects of acoustic streaming and hot-top unit type. Acoustic streaming characteristics were investigated first by using the earlier developed numerical model and water model experiments. Then, the acoustic streaming model was applied to develop a numerical code capable of simulating unsteady flow phenomena in the sump during the DC casting process. The results revealed that the introduction of ultrasonic vibrations into the melt in the hot-top unit had little or no effect on the temperature distribution and sump profile, but had a considerable effect on the melt flow pattern in the sump. Our results showed that ultrasound irradiation makes the flow velocity faster and produces a lot of relatively small eddies in the sump bulk and near the mushy zone. The latter causes frequently repeated thinning of the mushy zone layer. The numerical predictions were verified against measurements performed on a pilot DC caster producing 203 mm billets of Al-17%Si alloy. The verification revealed approximately the same sump depth and shape as those in the numerical simulations, and confirms the frequent and large fluctuations of the melt temperature during ultrasound irradiation. However, the measured temperature distribution in the sump significantly differed from that predicted numerically. This suggests that the present mathematical model should be further improved, particularly in terms of more accurate descriptions of boundary conditions and mushy zone characteristics.

scholarly journals Flow Structure Around Marginal Bank with Different Slopes Under the Action of Unsteady Flow

2018 ◽  
Author(s):  
Pingyi Wang ◽  
Ye Tian ◽  
Genting Guo ◽  
Meili Wang
Keyword(s):  
Unsteady Flow ◽  
Flow Pattern ◽  
Water Flow ◽  
Flow Structure ◽  
Fluid Motion ◽  
Maximum Flow ◽  
Water Area ◽  
Steep Slope ◽  
Surface Distribution ◽  
Average Flow Velocity

Unsteady flow is the most common and complicated form of fluid motion in nature. This paper takes the beaches of key waterways in the middle and lower reaches of the Yangtze River as the research object, analyzes the water surface distribution and average flow velocity distribution near the beach, and analyzes the differences. The relationship between the flow pattern of the steep slope and the water flow pattern of the entire survey area and the steep slope of the beach and its nearby water flow structure. The water flow near the beach is divided into four major blocks: the swelling water area, the falling water area, the backwater area and the maximum flow rate area. The water flow structure characteristics and the cause of each block are analyzed.

Experimental and Numerical Analysis of Pressure Pulsation in Francis Turbine

2008 ◽  
Author(s):  
Yexiang Xiao ◽  
Zhengwei Wang ◽  
Zongguo Yan ◽  
Yongyao Luo ◽  
Ruofu Xiao ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Flow Pattern ◽  
Pressure Fluctuation ◽  
Pressure Pulsation ◽  
Draft Tube ◽  
Flow Distribution ◽  
Internal Flow ◽  
Operating Conditions ◽  
Francis Turbine ◽  
Spiral Case

The pressure fluctuation taking place at the whole passage of a prototype Francis hydraulic turbine is studied by carrying out both experimental and numerical simulation. Unsteady wall pressure measurements at six different typical operating conditions are performs to thoroughly investigate pressure fields in the spiral case and straight draft tube dynamically. 3-D unsteady turbulent simulations are performed and compared to the experimental data. The computed flow domain includes the spiral case, stay vanes, guide vanes, rotating runner and the draft tube. The characteristic of unsteady flow and the pressure pulsation as well as their relationships are discussed in this paper, which also analyzed the correlation between the unsteady flow pattern and the pressure fluctuation at different parts of the turbine. In order to optimize the internal flow distribution in Francis turbines at partial loads, this paper presents some preliminary methods to control the unsteady flow pattern.

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