Stability of thermally driven shear flows in long inclined cavities with end-to-end temperature difference

1999 ◽  
Vol 42 (15) ◽  
pp. 2811-2822 ◽  
Author(s):  
R. Delgado-Buscalioni ◽  
E. Crespo del Arco
Keyword(s):  
Temperature Difference ◽  
Shear Flows ◽  
Thermally Driven ◽  
End To End

Long-ranged order in a thermally driven system with temperature dependent interactions

Soft Matter ◽  
2022 ◽  
Author(s):  
Rahul Karmakar ◽  
Jaydeb Chakrabarti
Keyword(s):  
Temperature Difference ◽  
Metallic Nanoparticles ◽  
Particle Interaction ◽  
Temperature Dependent ◽  
Driving Situation ◽  
Driven System ◽  
Thermally Driven

Aggregation of macro-molecules under external drive is far from understood. An important driving situation is achieved by temperature difference. The inter-particle interaction in metallic nanoparticles with ligand capping is reported...

scholarly journals A Simple Method Based on Routine Observations to Nowcast Down-Valley Flows in Shallow, Narrow Valleys

2016 ◽  
Vol 55 (7) ◽  
pp. 1497-1511 ◽  
Author(s):  
Gert-Jan Duine ◽  
Thierry Hedde ◽  
Pierre Roubin ◽  
Pierre Durand
Keyword(s):  
Temperature Difference ◽  
Potential Temperature ◽  
Threshold Value ◽  
Simple Relation ◽  
Forecast Verification ◽  
Valley Wind ◽  
Simple Method ◽  
Thermally Driven ◽  
Scale Down ◽  
Valley Flows

AbstractA simple relation to diagnose the existence of a thermally driven down-valley wind in a shallow (100 m deep) and narrow (1–2 km wide) valley based on routine weather measurements has been determined. The relation is based on a method that has been derived from a forecast verification principle. It consists of optimizing a threshold of permanently measured quantities to nowcast the thermally driven Cadarache (southeastern France) down-valley wind. Three parameters permanently observed at a 110-m-high tower have been examined: the potential temperature difference between the heights of 110 and 2 m, the wind speed at 110 m, and a bulk Richardson number. The thresholds are optimized using the wind observations obtained within the valley during the Katabatic Winds and Stability over Cadarache for the Dispersion of Effluents (KASCADE) field experiment, which was conducted in the winter of 2013. The highest predictability of the down-valley wind at the height of 10 m (correct nowcasting ratio of 0.90) was found for the potential temperature difference at a threshold value of 2.6 K. The applicability of the method to other heights of the down-valley wind (2 and 30 m) and to summer conditions is also demonstrated. This allowed a reconstruction of the climatology of the thermally driven down-valley wind that demonstrates that the wind exists throughout the year and is strongly linked to nighttime duration. This threshold technique will make it possible to forecast the subgrid-scale down-valley wind from operational numerical weather coarse-grid simulations by means of statistical downscaling.

Natural Convection in a Horizontal Porous Medium Subjected to an End-to-End Temperature Difference

1978 ◽  
Vol 100 (2) ◽  
pp. 191-198 ◽  
Author(s):  
A. Bejan ◽  
C. L. Tien
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Temperature Difference ◽  
Transfer Rate ◽  
Horizontal Cylinder ◽  
Horizontal Layer ◽  
Parallel Plates ◽  
End To End

Natural convection in a porous medium filling a slender horizontal space with an end-to-end temperature difference is studied analytically. The end-to-end temperature difference gives rise to a horizontal counterflow pattern augmenting the heat transfer rate through the porous medium. Two basic geometries are considered: horizontal layer confined between two adiabatic and impermeable parallel plates, and horizontal cylinder surrounded by an adiabatic and impermeable cylindrical surface. Nusselt number relations are derived in terms of the Rayleigh number and the cavity aspect ratio. The end-wall permeability is shown to affect the heat transfer rate through the medium.

On Studying Fluidic Motions in an Oscillating Heat Pipe

2013 ◽  
Vol 284-287 ◽  
pp. 513-517
Author(s):  
Han Ming Chen ◽  
Ching Ming Chiang ◽  
Kuo Hsiang Chien ◽  
Chi Chuan Wang
Keyword(s):  
Heat Pipe ◽  
Temperature Difference ◽  
Closed Loop ◽  
Operating Temperature ◽  
Lower Number ◽  
Liquid Ratio ◽  
Oscillating Heat Pipe ◽  
Thermally Driven ◽  
Higher Temperature ◽  
Channel Configuration

This study develops an analytical model applicable for predicting the fluidic motion of an oscillating heat pipe (OHP) with asymmetric arrayed channel configuration. The analytic model considers the temperature difference between the average evaporating region and the average condensing region as the thermally driven force for the fluidic motion. The calculated results show that the closed-loop OHP with asymmetric arrayed channel under lower number of turns, lower filled liquid ratio, higher operating temperature and higher temperature difference between the average evaporating region and the average condensing region for the frequency ratio of unity could attain a better performance of the fluidic motions.

A Numerical Study of Natural Convection in a Horizontal Porous Layer Subjected to an End-to-End Temperature Difference

1981 ◽  
Vol 103 (4) ◽  
pp. 797-802 ◽  
Author(s):  
C. E. Hickox ◽  
D. K. Gartling
Keyword(s):  
Finite Element ◽  
Natural Convection ◽  
Analytical Solution ◽  
Porous Layer ◽  
Temperature Difference ◽  
Numerical Study ◽  
Transfer Rates ◽  
Aspect Ratios ◽  
End To End ◽  
Temperature And Velocity Fields

A numerical study of steady, natural convection in a fluid-saturated, horizontal, porous layer subjected to an end-to-end temperature difference is reported. The analysis is performed using a finite element computer program based on the Galerkin form of the finite element method. Heat transfer rates are predicted for aspect ratios ranging from 0.1 to 0.5 and Rayleigh numbers in the range 25 to 200. Representative plots of temperature and velocity fields are presented. Comparisons are made with an approximate analytical solution and regions of validity are identified for the analytical solution.

scholarly journals Local-Scale Valley Wind Retrieval Using an Artificial Neural Network Applied to Routine Weather Observations

2019 ◽  
Vol 58 (5) ◽  
pp. 1007-1022
Author(s):  
Florian Dupuy ◽  
Gert-Jan Duine ◽  
Pierre Durand ◽  
Thierry Hedde ◽  
Pierre Roubin ◽  
...  
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Wind Speed ◽  
Temperature Difference ◽  
Potential Temperature ◽  
Winter Period ◽  
Valley Wind ◽  
Weather Observations ◽  
Thermally Driven ◽  
Artificial Neural

AbstractWe hereby present a new method with which to nowcast a thermally driven, downvalley wind using an artificial neural network (ANN) based on remote observations. The method allows the retrieval of wind speed and direction. The ANN was trained and evaluated using a 3-month winter-period dataset of routine weather observations made in and above the valley. The targeted valley winds feature two main directions (91% of the total dataset) that are aligned with the valley axis. They result from downward momentum transport, channeling mechanisms, and thermally driven flows. A selection procedure of the most pertinent ANN input variables, among the routine observations, highlighted three key variables: a potential temperature difference between the top and the bottom of the valley and the two wind components above the valley. These variables are directly related to the mechanisms that generate the valley winds. The performance of the ANN method improves on an earlier-proposed nowcasting method, based solely on a vertical temperature difference, as well as a multilinear regression model. The assessment of the wind speed and direction indicates good performance (i.e., wind speed bias of −0.28 m s−1 and 84% of calculated directions stray from observations by less than 45°). Major sources of error are due to the misrepresentation of cross-valley winds and very light winds. The validated method was then successfully applied to a 1-yr period with a similar performance. Potentially, this method could be used to downscale valley wind characteristics for unresolved valleys in mesoscale simulations.

scholarly journals Thermally driven exchange flow between open water and an aquatic canopy

2009 ◽  
Vol 632 ◽  
pp. 227-243 ◽  
Author(s):  
XUEYAN ZHANG ◽  
HEIDI M. NEPF
Keyword(s):  
Temperature Difference ◽  
Laboratory Experiments ◽  
Open Water ◽  
Scaling Analysis ◽  
Exchange Flow ◽  
Light Penetration ◽  
Constant Heat ◽  
Velocity Scale ◽  
Thermally Driven ◽  
Particle Imaging

Differential solar heating can result from shading by rooted emergent aquatic plants, producing a temperature difference between vegetated and unvegetated regions of a surface water body. This temperature difference will promote an exchange flow between the vegetation and open water. Drag associated with the submerged portion of the plants modifies this exchange, specifically, changing the dominant velocity scale. Scaling analysis predicts several distinct flow regimes, including inertia-dominated, drag-dominated and energy-limiting regimes. After a constant heat source is initiated, the flow is initially inertial, but quickly transitions to the drag-dominated regime. The energy-limiting regime is not likely to occur in the presence of rooted vegetation. Laboratory experiments describe the exchange flow and confirm the scaling analysis. Particle Imaging Velocimetry (PIV) was used to quantify the velocity field. Once the exchange flow enters the drag-dominated regime, the intrusion velocity uV is steady. The intrusion velocity decreases with increasing density of vegetation. The thickness of the intruding layer is set by the length scale of light penetration.

Surgical management of extracranial carotid artery aneurysms

VASA ◽  
2016 ◽  
Vol 45 (3) ◽  
pp. 223-228 ◽  
Author(s):  
Jan Paweł Skóra ◽  
Jacek Kurcz ◽  
Krzysztof Korta ◽  
Przemysław Szyber ◽  
Tadeusz Andrzej Dorobisz ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Surgical Management ◽  
Minor Stroke ◽  
Stroke Rate ◽  
Extracranial Carotid Artery ◽  
Long Term Follow Up ◽  
End To End ◽  
Dacron Patch ◽  
Major Stroke

Abstract. Background: We present the methods and results of the surgical management of extracranial carotid artery aneurysms (ECCA). Postoperative complications including early and late neurological events were analysed. Correlation between reconstruction techniques and morphology of ECCA was assessed in this retrospective study. Patients and methods: In total, 32 reconstructions of ECCA were performed in 31 symptomatic patients with a mean age of 59.2 (range 33 - 84) years. The causes of ECCA were divided among atherosclerosis (n = 25; 78.1 %), previous carotid endarterectomy with Dacron patch (n = 4; 12.5 %), iatrogenic injury (n = 2; 6.3 %) and infection (n = 1; 3.1 %). In 23 cases, intervention consisted of carotid bypass. Aneurysmectomy with end-to-end suture was performed in 4 cases. Aneurysmal resection with patching was done in 2 cases and aneurysmorrhaphy without patching in another 2 cases. In 1 case, ligature of the internal carotid artery (ICA) was required. Results: Technical success defined as the preservation of ICA patency was achieved in 31 cases (96.9 %). There was one perioperative death due to major stroke (3.1 %). Two cases of minor stroke occurred in the 30-day observation period (6.3 %). Three patients had a transient hypoglossal nerve palsy that subsided spontaneously (9.4 %). At a mean long-term follow-up of 68 months, there were no major or minor ipsilateral strokes or surgery-related deaths reported. In all 30 surviving patients (96.9 %), long-term clinical outcomes were free from ipsilateral neurological symptoms. Conclusions: Open surgery is a relatively safe method in the therapy of ECCA. Surgical repair of ECCAs can be associated with an acceptable major stroke rate and moderate minor stroke rate. Complication-free long-term outcomes can be achieved in as many as 96.9 % of patients. Aneurysmectomy with end-to-end anastomosis or bypass surgery can be implemented during open repair of ECCA.

Sign in / Sign up

Export Citation Format

Share Document