PIV and CFD studies on analyzing intragastric flow phenomena induced by peristalsis using a human gastric flow simulator

2014 ◽  
Vol 5 (8) ◽  
pp. 1839-1847 ◽  
Author(s):  
Hiroyuki Kozu ◽  
Isao Kobayashi ◽  
Marcos A. Neves ◽  
Mitsutoshi Nakajima ◽  
Kunihiko Uemura ◽  
...  
Keyword(s):  
Flow Field ◽  
Gastric Contents ◽  
Flow Phenomena ◽  
Gastric Peristalsis ◽  
Flow Simulator

The intragastric flow phenomena was analyzed using a human gastric flow simulator. The flow-field induced by gastric peristalsis was quantitatively measured in both liquid and liquid-solid gastric contents.

Analysis of Flow Phenomena in Gastric Contents Induced by Human Gastric Peristalsis Using CFD

2010 ◽  
Vol 5 (4) ◽  
pp. 330-336 ◽  
Author(s):  
Hiroyuki Kozu ◽  
Isao Kobayashi ◽  
Mitsutoshi Nakajima ◽  
Kunihiko Uemura ◽  
Seigo Sato ◽  
...  
Keyword(s):  
Gastric Contents ◽  
Flow Phenomena ◽  
Gastric Peristalsis

scholarly journals Aerothermal Investigations of Mixing Flow Phenomena in Case of Radially Inclined Ejection Holes at the Leading Edge

1999 ◽  
Author(s):  
Dieter E. Bohn ◽  
Karsten A. Kusterer
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Blade Surface ◽  
Cooling Fluid ◽  
Flow Phenomena ◽  
Vortex Systems

A leading edge cooling configuration is investigated numerically by application of a 3-D conjugate fluid flow and heat transfer solver, CHT-Flow. The code has been developed at the Institute of Steam and Gas Turbines, Aachen University of Technology. It works on the basis of an implicit finite volume method combined with a multi-block technique. The cooling configuration is an axial turbine blade cascade with leading edge ejection through two rows of cooling holes. The rows are located in the vicinity of the stagnation line, one row is on the suction side, the other row is on the pressure side. The cooling holes have a radial ejection angle of 45°. This configuration has been investigated experimentally by other authors and the results have been documented as a test case for numerical calculations of ejection flow phenomena. The numerical domain includes the internal cooling fluid supply, the radially inclined holes and the complete external flow field of the turbine vane in a high resolution grid. Periodic boundary conditions have been used in the radial direction. Thus, end wall effects have been excluded. The numerical investigations focus on the aerothermal mixing process in the cooling jets and the impact on the temperature distribution on the blade surface. The radial ejection angles lead to a fully three dimensional and asymmetric jet flow field. Within a secondary flow analysis it can be shown that complex vortex systems are formed in the ejection holes and in the cooling fluid jets. The secondary flow fields include asymmetric kidney vortex systems with one dominating vortex on the back side of the jets. The numerical and experimental data show a good agreement concerning the vortex development. The phenomena on the suction side and the pressure side are principally the same. It can be found that the jets are barely touching the blade surface as the dominating vortex transports hot gas under the jets. Thus, the cooling efficiency is reduced.

Visualization of Internal Flow Field of Propeller Fan

2017 ◽  
Author(s):  
Takaya Onishi ◽  
H. Sato ◽  
M. Hayakawa ◽  
Y. Kawata
Keyword(s):  
Flow Field ◽  
High Performance ◽  
Laser Light ◽  
Internal Flow ◽  
Light Sheet ◽  
Tip Vortex ◽  
Laser Light Sheet ◽  
Blade Surface ◽  
Similar Tendency ◽  
Flow Phenomena

Propeller fans are required not only to have high performance but also to be extremely quiet. The internal flow field of ventilation propeller fans is even more complicated because they usually have a very peculiar configuration with protruding blades upstream. Thus, many kinds of internal vortices yield which cause noise and their cause and countermeasures are needed to be clarified. The purposes of this paper are to visualize the internal flow of the propeller fan from the static and rotating frame of reference. The internal flow visualization measured from the static frame gives approximately the scale of the tip vortex. The visualization from the rotating coordinate system yields a better understanding of the flow phenomena occurring at the specific blade. The experiment is implemented by using a small camera mounted on the shaft of the fan and rotated it to capture the behavior of the vortices using a laser light sheet to irradiate the blade surface. Hence, the flow field of the specific blade could be understood to some extent. The visualized results are compared with the CFD results and these results show a similar tendency about the generation point and developing process of the tip vortex. In addition, it is found that the noise measurement result is relevant to the effect of tip vortex from the visualization result.

Performance of a Low Speed Axial Fan Under Distortion: An Experimental Investigation

2020 ◽  
Author(s):  
Sumit Tambe ◽  
Ugaitz Bartolomé Oseguera ◽  
Arvind Gangoli Rao
Keyword(s):  
Flow Field ◽  
Symmetry Plane ◽  
Vortex Pair ◽  
Axial Fan ◽  
Low Speed ◽  
Fan Performance ◽  
Fuel Burn ◽  
Flow Phenomena ◽  
Order Of Magnitude ◽  
Distortion Index

Abstract In the pursuit of reducing the fuel burn, future aircraft configurations will feature several types of improved propulsion systems, e.g. embedded engines with boundary layer ingestion, high-bypass ratio engines with short intakes, etc. Depending on the design and phase of flight, the engine fan will encounter inflow distortion of varying strength, and fan performance will be adversely affected. Therefore, investigation of the flow phenomena causing performance losses in fan and distortion interaction is important. This experimental study shows the effect of varying distortion index on four aspects of fan performance: distortion topology, upstream redistribution, performance curve, and flow unsteadiness. A low speed fan is tested under 60° circumferential distortion of varying strength, generated using distortion screens. The flow field in the upstream redistribution region is measured using PIV (planar and stereo). The fan performance is obtained using total pressure measurements. The noise spectra measured by a microphone are used to quantify the unsteadiness in the flow field. The distortion index (DC60) varies linearly with the grid porosity at constant wall thickness and aspect ratio of the grid cells. However, the distortion topology is significantly different as a stream-wise vortex pair appears in distorted flow at higher DC60. The vortices are stronger at higher DC60, but their order of magnitude is much lower than the circulation corresponding to fan itself. The spinner, distortion index and topology significantly affect the upstream redistribution mechanism. The vortex pair redistributes the flow which results in lower asymmetry in the symmetry plane. With increasing distortion, the performance is reduced and the unsteadiness is increased.

A New Approach to the Experimental Study of Turbomachinery Flow Phenomena

1977 ◽  
Vol 99 (1) ◽  
pp. 97-105 ◽  
Author(s):  
J. P. Gostelow
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Axial Flow ◽  
Centrifugal Pumps ◽  
New Approach ◽  
Static Pressure Distribution ◽  
Compressor Rotor ◽  
Flow Phenomena ◽  
On Line ◽  
Flow Compressor

Measurements of the unsteady flow field over a rotor and within its wake are needed in the development of most turbomachines. The technique advocated is that of data acquisition by on-line computer, using the periodic passing of a blade as a phase reference. The phase-lock averaging process is described as is its use in reducing the noise of raw data traces. Measurements of the unsteady flow over a cascade and of the resulting boundary layer behavior are presented. The approach was used in interpreting the unsteady flow field of an axial-flow compressor rotor and the static pressure distribution over the rotor tip. Finally the application to centrifugal pumps is discussed, enabling the designer to obtain information on the suction pressures and the extent of any separated region.

Analysis of Measurements in Vaned Diffusers of Centrifugal Compressors

1988 ◽  
Vol 110 (1) ◽  
pp. 115-121 ◽  
Author(s):  
W. Stein ◽  
M. Rautenberg
Keyword(s):  
Flow Field ◽  
Flow Structure ◽  
Calculation Method ◽  
Geometric Parameters ◽  
Variable Geometry ◽  
Centrifugal Compressors ◽  
Wide Range ◽  
Performance Curves ◽  
Different Types ◽  
Flow Phenomena

In vaned diffusers of centrifugal compressors many different flow phenomena interfere with one another, and different geometric parameters influence the flow field. Variations of these parameters allow the designer to optimize the diffuser for a certain application or to use a variable geometry for controlling the stage over a wide range. Two vaned diffusers that differ only in their passage widths are investigated using different types of measuring technique, in order to analyze the flow structure and to use it as a verification of a calculation method that allows detailed predictions of flow field parameters inside the diffuser, by taking into account geometric variations. Using this method predictions of the flow field of a variable geometry diffuser are made and are compared with the measured performance curves of the stage.

Unsteady Interaction of Labyrinth Seal Leakage Flow and Downstream Stator Flow in a Shrouded 1.5 Stage Axial Turbine

2005 ◽  
Author(s):  
P. Peters ◽  
J. R. Menter ◽  
H. Pfost ◽  
A. Giboni ◽  
K. Wolter
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Numerical Data ◽  
Labyrinth Seal ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Experimental Program ◽  
Leakage Flow ◽  
Axial Turbine ◽  
Flow Phenomena

This paper presents the results of experimental and numerical investigations into the flow in a 1.5-stage low-speed axial turbine with shrouded rotor blades and a straight through labyrinth seal. The paper focuses on the time dependent influence of the leakage flow on the downstream stator flow field. The experimental program consists of time accurate measurements of the three-dimensional properties of the flow through ten different measurement planes in the stator passage. The measurements were carried out using pneumatic five-hole probes and three dimensional hot-wire probes at the design operating point of the turbine. The measurement planes extend from the shroud to the casing. The complex three-dimensional flow field is mapped in great detail by 4,800 measurement points and 20 time steps per blade passing period. The time-accurate experimental data of the ten measurement planes was compared with the results of unsteady, numerical simulations of the turbine flow. The 3D-Navier-Stokes Solver CFX-TASCflow was used. The experimental and numerical results correspond well and allow detailed analysis of the flow phenomena. Additionally numerical data behind the rotor is used to connect the entry of the leakage flow with the flow phenomena in the downstream stator passage and behind it. The leakage flow causes strong fluctuations of the flow in the downstream stator. Above all, the high number of measurement points reveals both the secondary flow phenomena and the vortex structures within the blade passage. The time-dependence of both the position and the intensity of the vortices influenced by the leakage flow is shown. The paper shows that even at realistic clearance heights the leakage flow influences considerable parts of the downstream stator and gives rise to negative incidence and flow separation. Thus, labyrinth seal leakage flow should be taken properly into account in the design or optimization process of turbines.

Effects of the Steady Wake-Tip Clearance Vortex Interaction in a Compressor Cascade: Part II — Numerical Investigations

2014 ◽  
Author(s):  
Peter Busse ◽  
Andreas Krug ◽  
Konrad Vogeler
Keyword(s):  
Steady State ◽  
Flow Field ◽  
Initial Conditions ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Vortex Interaction ◽  
Compressor Cascade ◽  
Flow Phenomena ◽  
Tip Clearance Vortex ◽  
The Impact

An important aspect of the aerodynamic flow field in the tip region of axial compressor rotors is the unsteady interaction between the tip clearance vortex and the incoming stator wakes. In order to gain an improved understanding of the mechanics involved, systematic studies need to be performed. As a first step towards the characterisation of the dynamic effects caused by the relative movement of the blade rows, the impact of a stationary wake-induced inlet disturbance on a linear compressor cascade with tip clearance will be analyzed. The wakes were generated by a fixed grid of cylindrical bars with variable pitch being placed at discrete pitchwise positions. Part II of this two-part paper focuses on the numerical studies conducted with the scientific flow solver TRACE. Selected measurements, which are discussed in detail in the first part of this paper, are compared with steady state RANS simulation data to determine the validity of the computational model. For this purpose, the flow field obtained in the passage (PIV), at the cascade exit (five-hole probes) and the endwall pressure distributions were used. The presented numerical results show potentials and limitations of the steady state CFD for the prediction of the investigated flow phenomena. The computations provide the initial conditions for future unsteady calculations, and enable a separate depiction of potential effects of steady and unsteady wake-tip clearance vortex interaction.

Physics of Tip Clearance Flow in Turbomachinery (Keynote Paper)

2002 ◽  
Author(s):  
Masahiro Inoue ◽  
Masato Furukawa
Keyword(s):  
Flow Field ◽  
Physical Interpretation ◽  
Vortex Core ◽  
Vortical Structure ◽  
Three Dimensional ◽  
Axial Flow ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Flow Phenomena

In a recent advanced aerodynamic design of turbomachinery, the physical interpretation of three-dimensional flow field obtained by a numerical simulation is important for iterative modifications of the blade or impeller geometry. This paper describes an approach to the physical interpretation of the tip clearance flow in turbomachinery. First, typical flow phenomena of the tip clearance flow are outlined for axial and radial compressors, pumps and turbines to help comprehensive understanding of the tip clearance flow. Then, a vortex-core identification method which enables to extract the vortical structure from the complicated flow field is introduced, since elucidation of the vortical structure is essential to the physical interpretation of the tip clearance flow. By use of the vortex-core identification, some interesting phenomena of the tip clearance flows are interpreted, especially focussing on axial flow compressors.

Sign in / Sign up

Export Citation Format

Share Document