Multidimensional In-Cylinder Flow Calculations and Flow Visualization in a Motored Engine

Multidimensional simulations of coupled intake port/valve and in-cylinder flow structures in a pancake-shape combustion chamber engine are reported. The engine calculations include moving piston, moving intake valve, and valve stem. In order to verify the calculated results, qualitative flow visualization experiments were carried out for the same intake geometry during the induction process using a transient water analog. During the intake process the results of the multidimensional simulation agreed very well with the qualitative flow visualization experiments. An important finding in this study is the generation of a well-defined tumbling flow structure at BDC in the engine. In addition, this tumbling flow is sustained and amplified by the compression process and in turn causes generation of a high turbulence level before TDC. Many interesting features of the in-cylinder flow structures such as tumble, swirl, and global turbulent kinetic energy are discussed.

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The Effect of Intake Valve Angle on In-cylinder Flow during Intake and Compression Process

10.4271/2007-01-4045 ◽

2007 ◽

Cited By ~ 2

Author(s):

Myoungjin Kim ◽

Inyong Ohm

Keyword(s):

Intake Valve ◽

Compression Process ◽

Cylinder Flow ◽

Valve Angle

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CFD In-Cylinder Flow Simulation of an Engine and Flow Visualization

10.4271/950288 ◽

1995 ◽

Author(s):

Hisato Hori ◽

Tadao Ogawa ◽

Toshihiko Kuriyama

Keyword(s):

Flow Visualization ◽

Flow Simulation ◽

Cylinder Flow

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Effect of Corner-Arc on the Flow Structures Around a Square Cylinder

Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fluid Dynamics of Wind Energy; Bubble, Droplet, and Aerosol Dynamics ◽

10.1115/fedsm2018-83367 ◽

2018 ◽

Author(s):

Hariprasad Chakkalaparambil Many ◽

Vishnu Chandar Srinivasan ◽

Ajith Kumar Raghavan

Keyword(s):

Drag Reduction ◽

Oscillation Amplitude ◽

Water Channel ◽

Excitation Frequency ◽

Flow Structures ◽

Square Cylinder ◽

Near Wake ◽

Vortex Size ◽

Vortex Shedding Frequency ◽

Visualization Experiments

In this paper, flow structures around a corner modified square cylinder (side dimension, Bo) are presented and discussed. Cylinders with various corner arcs (circular) were considered (arc radius ‘r’). For various Corner Ratios (CR = r/Bo), values ranging from 0 to 0.5, flow visualization experiments were conducted in a water channel and the results are reported at Re = 2100 (based on Bo). Results presented are for two cases (a) stationary cylinders reporting the values of CD (coefficient of drag), St (Strouhal no.), and D (vortex size) and (b) oscillating cylinders at fe/fs = 1 (fe is the cylinder excitation frequency and fs is the vortex shedding frequency) and a/Bo = 0.8 (a is the cylinder oscillation amplitude). The work is aimed to explore the most effective configuration for drag reduction. Cylinder with corner ratio of 0.2 is proved to be the most effective one among the cases considered in this study with 19.3% drag reduction. As a major highlight, in contrast to the results of the previous studies, current study do not reveal a monotonous decrease of drag with increasing corner modification. Instead, it is shown here that, there is a specific value of CR ratio where the drag is the minimum most. A peculiar type of vortex structure was observed in the cases of stationary cylinders with CR > 0.2, contributing to the increase in drag. In the case of oscillating cylinders, description of one complete cycle for all CR ratios at various time instances are presented. The near-wake structures were observed to be dependent on the CR ratio. Counter intuitively, cylinder oscillation does not bring major difference in vortex size compared to the stationary case.

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A discussion on feeding cooler lubricant to the mesh exit region of a helical gear pair based on flow visualization experiments

International Gear Conference 2014: 26th–28th August 2014, Lyon ◽

10.1533/9781782421955.731 ◽

2014 ◽

pp. 731-740

Author(s):

H. Houjoh ◽

S. Matsumura ◽

S. Ohshima

Keyword(s):

Flow Visualization ◽

Helical Gear ◽

Gear Pair ◽

Exit Region ◽

Visualization Experiments ◽

Helical Gear Pair

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Three-dimensional surfactant-covered flows of thin liquid films on rotating cylinders

Journal of Fluid Mechanics ◽

10.1017/jfm.2018.153 ◽

2018 ◽

Vol 844 ◽

pp. 61-91 ◽

Cited By ~ 4

Author(s):

Weihua Li ◽

Satish Kumar

Keyword(s):

Free Surface ◽

Flow Visualization ◽

Evolution Equations ◽

Thin Liquid Film ◽

Three Dimensional ◽

Axial Direction ◽

Liquid Films ◽

Practical Applications ◽

Rotation Rates ◽

Visualization Experiments

The coating of discrete objects is an important but poorly understood step in the manufacturing of a broad variety of products. An important model problem is the flow of a thin liquid film on a rotating cylinder, where instabilities can arise and compromise coating uniformity. In this work, we use lubrication theory and flow visualization experiments to study the influence of surfactant on these flows. Two coupled evolution equations describing the variation of film thickness and concentration of insoluble surfactant as a function of time, the angular coordinate and the axial coordinate are solved numerically. The results show that surface-tension forces arising from both axial and angular variations in the angular curvature drive flows in the axial direction that tend to smooth out free-surface perturbations and lead to a stable speed window in which axial perturbations do not grow. The presence of surfactant leads to Marangoni stresses that can cause the stable speed window to disappear by driving flow that opposes the stabilizing flow. In addition, Marangoni stresses tend to reduce the spacing between droplets that form at low rotation rates, and reduce the growth rate of rings that form at high rotation rates. Flow visualization experiments yield observations that are qualitatively consistent with predictions from linear stability analysis and the simulation results. The visualizations also indicate that surfactants tend to suppress dripping, slow the development of free-surface perturbations, and reduce the shifting and merging of rings and droplets, allowing more time for solidifying coatings in practical applications.

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A Study of Unsteady Secondary Flow in a Water Flow Axial Turbine Model

Volume 6: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2008-50239 ◽

2008 ◽

Cited By ~ 2

Author(s):

Christian Kasper ◽

Martin G. Rose ◽

Stephan Staudacher ◽

Jochen Gier

Keyword(s):

Flow Visualization ◽

Vortex Breakdown ◽

Water Channel ◽

Leading Edge ◽

Secondary Flows ◽

Stagnation Region ◽

Spiral Vortex ◽

Passage Vortex ◽

High Turbulence ◽

First Time

The influence of secondary flows on the performance of turbines has been investigated in great detail in the last decades. The interaction of vortices with following blade rows has been identified to be one of the loss mechanisms within a turbo-machine. This paper presents for the first time detailed flow visualization photographs of the interaction of the vane passage vortex with the rotor. The appearance vortex breakdown could be identified before and within the rotating passage of the turbine. The measurements were taken in a vertical water channel. Water is used instead of air because the flow visualization can be realised very easily with injected ink. For different relative positions of rotor to stator a series of photographs were taken. With an image editing process the average and the pixel RMS were calculated for each relative position. The pixel RMS is a useful indicator to identify highly turbulent regions in the flow field. The photographs of the vortex breakdown show spots of high pixel RMS which are associated with very high turbulence and therefore can be regarded as sources of loss. Insight is gained into the nature of the passage vortex breakdown mechanisms as follows: first the pressure wave of the rotor stretches the vortex causing a spiral vortex instability, then the vortex interacts with the leading edge as it attempts to cut the vortex. In the stagnation region of the blade a bubble type instability forms, expands and then convects through the rotor. The absolute trajectory of the vortex fluid reveals that it exchanges no work with the rotor.

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Hydrodynamic drag of two frog species: Hymenochirus boettgeri and Rana pipiens

Canadian Journal of Zoology ◽

10.1139/z87-172 ◽

1987 ◽

Vol 65 (5) ◽

pp. 1085-1090 ◽

Cited By ~ 6

Author(s):

Julianna M. Gal ◽

R. W. Blake

Keyword(s):

Flow Visualization ◽

Rana Pipiens ◽

Swimming Performance ◽

The Body ◽

Hydrodynamic Drag ◽

Subtraction Method ◽

Flat Plates ◽

Hind Limbs ◽

Hymenochirus Boettgeri ◽

Visualization Experiments

Drag of the aquatic frog Hymenochirus boettgeri was investigated by a series of drop-tank and flow visualization experiments. The maximum drag coefficient (CD) of the body and hind limbs was 0.24–0.11, for a Reynolds number (Re) of 1500–8000. Results of the flow visualization experiment support the CD values obtained for the body and hind limbs of H. boettgeri. CD similarly measured for Rana pipiens was 0.060–0.050, for a Re range of 16 600 – 40 400. A comparison of CD under dynamically similar conditions suggests that jumping may not compromise swimming performance in these two species. CD for the foot of H. boettgeri was examined by three methods: drop-tank experiments with isolated frog's feet and with isolated acetate model feet, and a subtraction method. CD for the isolated foot was 2.5–1.6 for 100 < Re < 700. Results were similar to those obtained with isolated model feet, where 1.8 > CD > 1.2 for 300 < Re < 1300. The subtraction method gave similar results to those obtained from drop-tank experiments with isolated model and real feet, within the Re range of 300–3000. The results of all three methods and flow visualization experiments support the assumption that animal paddles can be treated as three-dimensional flat plates, oriented normal to the direction of flow.

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