An Experimental Study and Analysis of Turbulent Film Tilted Pad Bearings

1974 ◽  
Vol 96 (1) ◽  
pp. 168-173 ◽  
Author(s):  
R. A. Burton ◽  
H. J. Carper ◽  
Y. C. Hsu
Keyword(s):  
Experimental Study ◽  
Turbulent Flow ◽  
Large Scale ◽  
Velocity Profiles ◽  
Working Fluid ◽  
Pressure Distributions ◽  
Aspect Ratios

Velocity profiles and pressure distributions are reported for turbulent flow under tilted pads in a large scale bearing model (6-ft shaft size, with air as the working fluid). Results are extended analytically to other bearing sizes and aspect ratios.

scholarly journals Jump rope vortex in liquid metal convection

2018 ◽  
Vol 115 (50) ◽  
pp. 12674-12679 ◽  
Author(s):  
Tobias Vogt ◽  
Susanne Horn ◽  
Alexander M. Grannan ◽  
Jonathan M. Aurnou
Keyword(s):  
Numerical Experiments ◽  
Large Scale ◽  
Industrial Applications ◽  
Viscous Fluids ◽  
Working Fluid ◽  
Liquid Gallium ◽  
Natural Systems ◽  
Convective Systems ◽  
Aspect Ratios ◽  
Jump Rope

Understanding large-scale circulations (LSCs) in turbulent convective systems is important for the study of stars, planets, and in many industrial applications. The canonical model of the LSC is quasi-planar with additional horizontal sloshing and torsional modes [Brown E, Ahlers G (2009) J Fluid Mech 638:383–400; Funfschilling D, Ahlers G (2004) Phys Rev Lett 92:194502; Xi HD et al. (2009) Phys Rev Lett 102:044503; Zhou Q et al. (2009) J Fluid Mech 630:367–390]. Using liquid gallium as the working fluid, we show, via coupled laboratory-numerical experiments in tanks with aspect ratios greater than unity (Γ∈{2, 2}), that the LSC takes instead the form of a “jump rope vortex,” a strongly 3D mode that periodically orbits around the tank following a motion much like a jump rope on a playground. Further experiments show that this jump rope flow also exists in more viscous fluids such as water, albeit with a far smaller signal. Thus, this jump rope mode is an essential component of the turbulent convection that underlies our observations of natural systems.

Experimental Study of Turbulent Flow Induced by Regular and Irregular Waves Above a Rock-Armored Slope

2014 ◽  
Author(s):  
Konstantina A. Galani ◽  
Giannis D. Dimou ◽  
Athanassios A. Dimas
Keyword(s):  
Experimental Study ◽  
Turbulent Flow ◽  
Velocity Profiles ◽  
Irregular Waves ◽  
Wave Crest ◽  
Regular Waves ◽  
Mean Velocity ◽  
Peak Period ◽  
Wave Trough ◽  
Wave Heights

The aim of the present work is the experimental study of the turbulent flow induced by waves above a physical model of a rock-armored slope of 1/3. The armor consisted of two layers of rocks with characteristic diameter D50 = 4.4cm. Measurements of the instantaneous velocity fields were conducted using an underwater planar PIV system. Four cases of incoming waves were tested, two cases of regular waves of 1st order Stokes theory with wave period of 1.134s and wave heights of 0.04m and 0.08m, respectively, and two cases of irregular waves, generated from a JONSWAP spectrum, with a peak period of 1.134s and significant wave heights of 0.04m and 0.08m, respectively. For the regular waves, the period-averaged velocity profiles show the existence of a strong undertow current heading towards deep water, while turbulence is not homogeneous with larger horizontal fluctuations. The phase-averaged horizontal velocity profiles present systematically larger values during wave trough passage than during wave crest passage. Furthermore, as the depth becomes smaller, the waveform loses its symmetry, with the wave trough becoming wider and the wave crest steeper. For the irregular waves, the mean velocity profiles show the existence of an undertow current weaker in magnitude than the one in the regular waves, while turbulence is still not homogeneous with larger horizontal fluctuations. For both wave cases, spanwise vorticity, which is generated at the rough surface of the rock-armored slope, is transported landward by the turbulent velocities.

Effectiveness of Small Onshore Seawall in Reducing Forces Induced by Tsunami Bore: Large Scale Experimental Study

2009 ◽  
Vol 4 (6) ◽  
pp. 382-390 ◽  
Author(s):  
Mary Elizabeth Oshnack ◽  
◽  
Francisco Aguíñiga ◽  
Daniel Cox ◽  
Rakesh Gupta ◽  
...  
Keyword(s):  
Experimental Study ◽  
Large Scale ◽  
Rigid Wall ◽  
Wave Profile ◽  
Small Individual ◽  
Wave Flume ◽  
Pressure Distributions ◽  
Field Reconnaissance ◽  
Wave Heights ◽  
Wire Resistance

Tsunami force and pressure distributions on a rigid wall fronted by a small seawall were determined experimentally in a large-scale wave flume. Six different seawall heights were examined, two of which were exposed to a range of solitary wave heights. The same experiment was done without a seawall for comparison. The measured wave profile contained incident offshore, incident broken, reflected broken, and transmitted wave heights measured using wire resistance and ultrasonic wave gauges. Small individual seawalls increased reflection of the incoming broken bore front and reduced force on the rigid landward wall. These findings agree well with published field reconnaissance on small seawalls in Thailand that showed a correlation between seawalls and reduced damage on landward structures.

An Experimental Study of Natural Convection in a Rectangular Enclosure Using PIV Measurement Techniques

2011 ◽  
Author(s):  
K. M. Akyuzlu ◽  
J. Farkas
Keyword(s):  
Experimental Study ◽  
Natural Convection ◽  
Measurement Techniques ◽  
Flow Patterns ◽  
Working Fluid ◽  
Two Dimensional ◽  
Rectangular Enclosure ◽  
Aspect Ratios ◽  
Circulation Patterns ◽  
Piv Measurement

An experimental study is conducted to determine the circulation patterns inside a rectangular enclosure due to natural convection using a Particle Image Velocimeter (PIV). Experiments were conducted using two different fluids (air and water) and for rectangular enclosures with aspect ratios 0.5 and 1.0. Natural convection in enclosures has been experimentally studied in the past. Many of these studies cited in the literature use some kind of an optical method like interferograms, shadowgraphs, streak photographs, or multi-exposure photographs to visualize the flow patterns in the enclosure. The present study employs a commercial two-dimensional PIV to capture, instantaneously, the circulation patterns inside the test section. The test cavity in the present setup is of rectangular shape, which is 5 inches (127 mm) wide, where the height of the enclosure can be changed to obtain aspect ratios of 0.5 and 1.0. The depth of the rectangular enclosure measures 12 inches (305 mm) to minimize the effect of walls normal to the two dimensional flow patterns that are expected in this type of arrangement. The walls of the cavity are made of Aluminum plates. These plates are kept at constant but different temperatures during the experiments. In the present study, hollow glass sphere particles with 10 microns in diameter were used as seeding for water experiments and fine particles/flakes of ash generated from burned incense were used as seeding in the air experiments. For each working fluid, the experiments were repeated for different aspect ratios and for different wall temperature differences which corresponded to Rayleigh numbers in the range of 106 and 107. Velocity fields were captured at steady state for each experiment using the two-dimensional PIV system. Numerical studies were also carried out using a commercial CFD software. Comparisons of the numerical and experimental results indicate a good match in terms of circulation patterns and velocity magnitudes in the core of the buoyancy driven flow. Discrepancies in measured and predicted values of velocities are more pronounced near to the boundaries of the enclosure. Separate measurements with finer interrogation areas and different PIV setting were required to improve the accuracy of the measurements near the corners (top and bottom) of the enclosure. The results of these measurements are also presented.

An Experimental Study of Annular Flows With Applications in Turbulent Film Lubrication

1967 ◽  
Vol 89 (3) ◽  
pp. 381-391 ◽  
Author(s):  
R. A. Burton ◽  
H. J. Carper
Keyword(s):  
Experimental Study ◽  
Shear Stress ◽  
Turbulent Flows ◽  
Large Scale ◽  
Journal Bearings ◽  
Major Influence ◽  
Plane Couette Flow ◽  
Pressure Distributions ◽  
Large Pressure ◽  
Film Lubrication

Experiments are reported on turbulent flows in air, in a large-scale bearing model of 6-ft dia, 2-ft length, 0.54-in. film thickness. Simulation of tilted pads, short journal bearings, and stepped pads is described. Pressure distributions are reported along with velocity and turbulence-intensity profiles. Wall shear stress is computed from the velocity profile measurements. The variations of these factors are compared with available data for plane Couette flow, wall law flow, and pressure flow in pipes, and the relationships among these are discussed. In addition, large pressure jumps at discontinuities are reported, and are shown to provide a major influence on the overall pressure distributions.

Enhanced Heat Transfer Due to Secondary Flows in Mixed Turbulent Convection

1987 ◽  
Vol 109 (4) ◽  
pp. 943-946 ◽  
Author(s):  
L. W. Swanson ◽  
I. Catton
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Secondary Flows ◽  
Turbulent Convection ◽  
Working Fluid ◽  
Mean Flow ◽  
Enhanced Heat Transfer ◽  
Flow And Heat Transfer ◽  
Aspect Ratios ◽  
Single Flow

An experimental study of the fluid flow and heat transfer phenomena associated with opposing mixed turbulent convection in vertical ducts has been conducted. The duct considered had vertical and horizontal aspect ratios of 24.4 and 9.7, respectively. The working fluid was Freon-113, providing a Prandtl number of approximately 6.5. The results showed that a number of flow bifurcations occurred as GrDh/ReDh2 was increased. The first bifurcation observed was from parallel turbulent mean flow to a large single flow cell in the x−z plane. This occurred in the neighborhood of GrDh/ReDh2 = 2. Further bifurcations to multiple cells and eventually pure large-scale chaos were also observed. A correlation for the enhanced heat transfer was found to be NuDh/NuDh,0 = 1.0 + 0.9[ln(GrDh/ReDh2 + 1)]1.39, where NuDh,0 is the Petukhov–Virillov correlation for pure forced turbulent convection.

An experimental study of kicked thermal turbulence

2008 ◽  
Vol 606 ◽  
pp. 133-151 ◽  
Author(s):  
XIAO-LI JIN ◽  
KE-QING XIA
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Turbulent Flow ◽  
Time Scale ◽  
Energy Input ◽  
Large Scale ◽  
Saturation Level ◽  
Convective System ◽  
Input Energy ◽  
Thermal Turbulence

We present an experimental study of turbulent Rayleigh–Bénard convection (RBC) in which the input energy that drives the turbulent flow is in the form of periodical pulses. A surprising finding of the study is that in this ‘kicked’ thermal turbulence the heat transfer efficiency is enhanced compared to both constant and sinusoidally modulated energy inputs. For the apparatus used in the present study, an enhancement of 7% of the dimensionless Nusselt number Nu has been achieved. The enhancement is found to depend on two factors. One is the synchronization of the kicking period of energy input with the intrinsic time scale of the turbulent flow. When the repetition period of the input energy pulse equals half of the large-scale flow turnover time, a resonance or optimization of the enhancement is achieved. The other factor is the pulse shape (the inverse square of the energy input duty cycle). We find that a spiky pulse is more efficient for heat transfer than a flatter one of the same energy. It is found that in this kicked thermal turbulence there exist appropriate ranges of the kicking strength A and the kicking frequency f in which the Rayleigh number Ra grows to a saturation level and that the saturated Ra fluctuates between a lower saturation level $Ra_{l}^{sat}$ and an upper saturation level $Ra_{u}^{sat}$. For large enough saturated Ra, power-law dependences on f and A are found: $Ra_{l}^{sat}\propto (Af)^{0.80\pm0.02}$ and $Ra_{u}^{sat}\propto f^{0.70\pm0.01}A^{0.84\pm0.02}$. The scaling law for $Ra_{l}^{sat}$ is found to agree quantitatively with the prediction of a mean-field theory of kicked turbulence (Lohse, Phys. Rev. E vol. 62, 2000, p. 4946) when the latter is appropriately extended to the case of kicked thermal turbulence. It is further found that a large-scale circulatory flow (LSC) still exists in the kicked RBC, and that its Reynolds number has the same scaling with Ra as in the steadily driven case, i.e. Ref ∝ Ra0.46±0.01. The present study provides an example of achieving enhanced heat transfer in a convective system by first triggering the emission of clustered thermal plumes via an active control and then synchronizing the transport of the plume clusters with an internal time scale.

Experimental study of thermohydraulic characteristics and irreversibility analysis of novel axial corrugated tube with spring tape inserts

2020 ◽  
Vol 92 (3) ◽  
pp. 30901
Author(s):  
Suvanjan Bhattacharyya ◽  
Debraj Sarkar ◽  
Ulavathi Shettar Mahabaleshwar ◽  
Manoj K. Soni ◽  
M. Mohanraj
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Performance ◽  
Working Fluid ◽  
The Novel ◽  
Heat Exchanger Tube ◽  
Heat Transfer Augmentation ◽  
Corrugated Tube ◽  
The Impact ◽  
Exchanger Tube

The current study experimentally investigates the heat transfer augmentation on the novel axial corrugated heat exchanger tube in which the spring tape is introduced. Air (Pr = 0.707) is used as a working fluid. In order to augment the thermohydraulic performance, a corrugated tube with inserts is offered. The experimental study is further extended by varying the important parameters like spring ratio (y = 1.5, 2.0, 2.5) and Reynolds number (Re = 10 000–52 000). The angular pitch between the two neighboring corrugations and the angle of the corrugation is kept constant through the experiments at β = 1200 and α = 600 respectively, while two different corrugations heights (h) are analyzed. While increasing the corrugation height and decreasing the spring ratio, the impact of the swirling effect improves the thermal performance of the system. The maximum thermal performance is obtained when the corrugation height is h = 0.2 and spring ratio y = 1.5. Eventually, correlations for predicting friction factor (f) and Nusselt number (Nu) are developed.

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