Effect of Component Layout and Geometry on the Flow Distribution in Electronics Circuit Packs

1991 ◽  
Vol 113 (1) ◽  
pp. 50-57 ◽  
Author(s):  
K. Azar ◽  
E. T. Russell
Keyword(s):  
Experimental Investigation ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Reynolds Numbers ◽  
Water Tunnel ◽  
Large Aspect Ratio ◽  
Electronic Components ◽  
Component Layout ◽  
Multiple Component ◽  
The Impact

An experimental investigation was conducted to study the impact of component layout and geometry on flow distribution on a circuit pack. The experiment was conducted in a water tunnel using aluminum blocks to simulate various electronic components. The experiments were conducted for laminar and onset of transition Reynolds numbers. Diluted ink was used as the flow visualization vehicle. The study looked at flow over single component, multiple component, and fully loaded circuit packs. The study drew a number of conclusions including the flows were highly three dimensional, and location and orientation of components with large aspect ratio will significantly affect circuit pack flow distribution.

Vortex rings impinging on walls: axisymmetric and three-dimensional simulations

1993 ◽  
Vol 256 ◽  
pp. 615-646 ◽  
Author(s):  
Paolo Orlandi ◽  
Roberto Verzicco
Keyword(s):  
Numerical Simulations ◽  
Strain Tensor ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Vortex Rings ◽  
Compression Phase ◽  
Vortex Pairing ◽  
The Impact ◽  
Good Agreement ◽  
Three Dimensional Simulations

Accurate numerical simulations of vortex rings impinging on flat boundaries revealed the same features observed in experiments. The results for the impact with a free-slip wall compared very well with previous numerical simulations that used spectral methods, and were also in qualitative agreement with experiments. The present simulation is mainly devoted to studying the more realistic case of rings interacting with a no-slip wall, experimentally studied by Walker et al. (1987). All the Reynolds numbers studied showed a very good agreement between experiments and simulations, and, at Rev > 1000 the ejection of a new ring from the wall was seen. Axisymmetric simulations demonstrated that vortex pairing is the physical mechanism producing the ejection of the new ring. Three-dimensional simulations were also performed to investigate the effects of azimuthal instabilities. These simulations have confirmed that high-wavenumber instabilities originate in the compression phase of the secondary ring within the primary one. The large instability of the secondary ring has been explained by analysis of the rate-of-strain tensor and vorticity alignment. The differences between passive scalars and the vorticity field have been also investigated.

Low Reynolds numbers flow past an ellipsoid of revolution of large aspect ratio

1965 ◽  
Vol 23 (4) ◽  
pp. 657-671 ◽  
Author(s):  
Yun-Yuan Shi
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Three Dimensional ◽  
Major Axis ◽  
Reynolds Numbers ◽  
The Body ◽  
Large Aspect Ratio ◽  
Low Reynolds Numbers ◽  
Ellipsoid Of Revolution ◽  
Limiting Case

The results of Proudman & Pearson (1957) and Kaplun & Lagerstrom (1957) for a sphere and a cylinder are generalized to study an ellipsoid of revolution of large aspect ratio with its axis of revolution perpendicular to the uniform flow at infinity. The limiting case, where the Reynolds number based on the minor axis of the ellipsoid is small while the other Reynolds number based on the major axis is fixed, is studied. The following points are deduced: (1) although the body is three-dimensional the expansion is in inverse power of the logarithm of the Reynolds number as the case of a two-dimensional circular cylinder; (2) the existence of the ends and the variation of the diameter along the axis of revolution have no effect on the drag to the first order; (3) a formula for drag is obtained to higher order.

THE MECHANISM OF SHOCK COMMINUTION OF 3D C/SIC COMPOSITE SUBJECTED TO HIGH VELOCITY IMPACT

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1510-1517
Author(s):  
QINGMING ZHANG ◽  
FENGLEI HUANG ◽  
LI CHEN ◽  
LIMING HAN ◽  
JINZHU LI
Keyword(s):  
Experimental Investigation ◽  
High Velocity ◽  
Ceramic Matrix Composite ◽  
Three Dimensional ◽  
Ceramic Matrix ◽  
Impact Point ◽  
High Velocity Impact ◽  
Velocity Impact ◽  
Sic Ceramic ◽  
The Impact

In this paper, experimental investigation and theoretical analysis are carried out in an attempt to study the response of SiC ceramic matrix composite reinforced with three dimensional braided fabric(3 D C/SiC ) under high velocity impact. The results show that 3 D C/SiC composite will be turned into comminution if the pressure of the impact point resulted from the projectile impacting 3 D C/SiC composite sample is larger than 780Mpa. Based on the analysis of the mechanism of composite comminution, a theoretical model has been developed.

scholarly journals Assessment of Machine-Learned Turbulence Models Trained for Improved Wake-Mixing in Low-Pressure Turbine Flows

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8327
Author(s):  
Roberto Pacciani ◽  
Michele Marconcini ◽  
Francesco Bertini ◽  
Simone Rosa Taddei ◽  
Ennio Spano ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Computational Domain ◽  
Trailing Edge ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Turbulence Closures ◽  
The Impact

This paper presents an assessment of machine-learned turbulence closures, trained for improving wake-mixing prediction, in the context of LPT flows. To this end, a three-dimensional cascade of industrial relevance, representative of modern LPT bladings, was analyzed, using a state-of-the-art RANS approach, over a wide range of Reynolds numbers. To ensure that the wake originates from correctly reproduced blade boundary-layers, preliminary analyses were carried out to check for the impact of transition closures, and the best-performing numerical setup was identified. Two different machine-learned closures were considered. They were applied in a prescribed region downstream of the blade trailing edge, excluding the endwall boundary layers. A sensitivity analysis to the distance from the trailing edge at which they are activated is presented in order to assess their applicability to the whole wake affected portion of the computational domain and outside the training region. It is shown how the best-performing closure can provide results in very good agreement with the experimental data in terms of wake loss profiles, with substantial improvements relative to traditional turbulence models. The discussed analysis also provides guidelines for defining an automated zonal application of turbulence closures trained for wake-mixing predictions.

New thermal-hydraulic correlations for printed circuit heat exchangers (PCHEs) with zigzag channels under high Reynolds numbers

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Carolina P. Naveira-Cotta ◽  
Jian Su ◽  
Paulo Lucena Kreppel Paes ◽  
Philippe R. Egmont ◽  
Rodrigo P. M. Moreira ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Design Parameters ◽  
Channel Diameter ◽  
Content Type ◽  
Printed Circuit ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
The Impact

Purpose The purpose of this paper is to investigate the impact of semi-circular zigzag-channel printed circuit heat exchanger (PCHE) design parameters on heat transfer and pressure drop of flows under high Reynolds numbers and provide new thermal-hydraulic correlations relevant to conditions encountered in natural gas processing plants. Design/methodology/approach The correlations were developed using three-dimensional steady-state computational fluid dynamics simulations with varying semicircular channel diameter (from 1 to 5 mm), zigzag angle (from 15° to 45°) and Reynolds number (from 40,000 to 100,000). The simulation results were validated by comparison with experimental results and existing correlations. Findings The results revealed that the thermal-hydraulic performance was mostly affected by the zigzag angle, followed by the ratio of the zigzag channel length to the hydraulic diameter. Overall, smaller zigzag angles favored heat transfer intensification while keeping reasonably low pressure drops. Originality/value This study is, to date, the only one providing thermal-hydraulic correlations for PCHEs with zigzag channels under high Reynolds numbers. Besides, the broad range of parameters considered makes the proposed correlations valuable PCHE design tools.

Impact of three-dimensional phenomena on the design of rotodynamic pumps

1999 ◽  
Vol 213 (1) ◽  
pp. 59-70 ◽  
Author(s):  
J. F. Gülich
Keyword(s):  
Three Dimensional ◽  
Flow Distribution ◽  
Navier Stokes ◽  
Specific Work ◽  
Preliminary Design ◽  
Present Contribution ◽  
Part Load ◽  
Starting Point ◽  
Flow Features ◽  
The Impact

Three-dimensional Navier—Stokes calculations are expected to be increasingly applied in the future for performance improvement of rotodynamic pumps. Frequently such an optimization process involves a preliminary design—based on one-dimensional methods and empirical data—which is subsequently optimized by computational fluid dynamics (CFD). Employing an empirical database is not only necessary in order to provide a good starting point for the CFD analysis but also to ensure that the design has a good chance of fulfilling part load requirements, since recirculating flows at the impeller inlet and outlet are not easily handled by CFD programs. CFD calculations provide the specific work input to the fluid and information on losses and reveal the complex three-dimensional flow patterns. The designer is faced with the task of interpreting such data and drawing conclusions for the optimization of the impeller. It is the purpose of the present contribution to analyse and describe the impact of various geometric parameters and flow features on the velocity distribution in the impeller and their influence on performance and part load characteristics. Criteria are also provided to select the parameters for the preliminary design. Hydraulic impeller losses calculated by CFD programs may often be misleading if the non-uniformity of the flow distribution at the impeller outlet is ignored. Procedures to quantify such mixing losses in the diffuser or volute downstream of the impeller are discussed.

Optimal Three-Dimensional Placement of Heat Generating Electronic Components

1997 ◽  
Vol 119 (2) ◽  
pp. 106-113 ◽  
Author(s):  
M. I. Campbell ◽  
C. H. Amon ◽  
J. Cagan
Keyword(s):  
Simulated Annealing ◽  
Simulated Annealing Algorithm ◽  
Three Dimensional ◽  
Heat Transfer Analysis ◽  
Placement Test ◽  
Test Cases ◽  
Electronic Components ◽  
Component Layout ◽  
Temperature Ranges ◽  
Annealing Algorithm

This work introduces an algorithm that uses simulated annealing to perform electronic component layout while incorporating constraints related to thermal performance. A hierarchical heat transfer analysis is developed which is used in conjunction with the simulated annealing algorithm to produce final layout configurations that are densely packed and operate within specified temperature ranges. Examples of three-dimensional component placement test cases are presented including an application to embedded wearable computers.

scholarly journals Reduction of Tip Clearance Losses Through 3-D Airfoil Designs

1996 ◽  
Author(s):  
J. Brent Staubach ◽  
Om P. Sharma ◽  
Gary M. Stetson
Keyword(s):  
Numerical Experiments ◽  
Three Dimensional ◽  
Full Scale ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Water Tunnel ◽  
Design Concepts ◽  
Overall Design ◽  
Physical Experiments ◽  
The Impact

Results are presented from a program, conducted to investigate the impact of spanwise stacking of turbine airfoil sections on tip clearance flows. Numerical as well as physical experiments were performed to demonstrate that these airfoils yielded about 40% reduction in tip clearance losses compared to those designed with a conventional approach. Three dimensional, steady Euler and Reynolds Averaged Navier Stokes (RANS) codes were used to execute the numerical experiments. Initial physical experiments were performed in a water tunnel by using linear cascades to validate the design concepts. The verification of the overall design concepts was executed in an uncooled full scale rotating rig.

scholarly journals Experimental investigation of flow behind a cube for moderate Reynolds numbers

2014 ◽  
Vol 750 ◽  
pp. 73-98 ◽  
Author(s):  
L. Klotz ◽  
S. Goujon-Durand ◽  
J. Rokicki ◽  
J. E. Wesfreid
Keyword(s):  
Numerical Simulation ◽  
Experimental Investigation ◽  
Particle Image Velocimetry ◽  
Bluff Body ◽  
Particle Image ◽  
Reynolds Numbers ◽  
Laser Induced Fluorescence ◽  
Basic Flow ◽  
Water Tunnel ◽  
Image Velocimetry

AbstractThe wake behind a cube with a face normal to the flow was investigated experimentally in a water tunnel using laser induced fluorescence (LIF) visualisation and particle image velocimetry (PIV) techniques. Measurements were carried out for moderate Reynolds numbers between 100 and 400 and in this range a sequence of two flow bifurcations was confirmed. Values for both onsets were determined in the framework of Landau’s instability model. The measured longitudinal vorticity was separated into three components corresponding to each of the identified regimes. It was shown that the vorticity associated with a basic flow regime originates from corners of the bluff body, in contrast to the two other contributions which are related to instability effects. The present experimental results are compared with numerical simulation carried out earlier by Saha (Phys. Fluids, vol. 16, 2004, pp. 1630–1646).

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