Leidenfrost drop dynamics: a forgotten past and modern day rediscoveries

2021 ◽  
Author(s):  
Seán Stewart
Keyword(s):  
Thin Layer ◽  
Boiling Point ◽  
Dynamic Behaviour ◽  
Dynamical Behaviour ◽  
Drop Dynamics ◽  
Leidenfrost Effect ◽  
History Of ◽  
Hot Surface

Abstract When drops of liquid are placed onto highly heated substrates at temperatures well above their boiling point, the drops float on a thin layer of vapour formed between the liquid and the hot surface. In a 290 year old phenomenon referred to as the Leidenfrost effect, drops freed from contact with the surface below can undergo a range of surprising and unexpected dynamical behaviour. In this paper we trace various early developments associated with the dynamics of Leidenfrost drops. By showing how many of the more recent discoveries found in the dynamic behaviour of Leidenfrost drops were either anticipated or antedated, we hope to draw attention to the long, rich, and largely overlooked history of the Leidenfrost effect and show there is much one can learn from its forgotten past.

scholarly journals Conflict in the Middle East: The US and the Turkish-Kurdish Conflict

2018 ◽  
Vol 25 ◽  
pp. 11-21
Author(s):  
Matthew Dotzler
Keyword(s):  
United States ◽  
Foreign Policy ◽  
National Security ◽  
Boiling Point ◽  
The United States ◽  
Us Foreign Policy ◽  
Northern Iraq ◽  
The Us ◽  
History Of ◽  
Kurdish Conflict

The conflict between Turkey and the Kurds is once again reaching a boiling point. Following the defeat of ISIL in northern Iraq and Syria, Turkey is now concerned that the returning Kurdish militias pose a threat to its national security. The United States, as an ally to both parties, finds itself in a unique position to push for diplomatic solutions and to mediate the conflict before it grows out of control once again. This paper will examine the history of the Turkish-Kurdish conflict, the actors involved, and how US foreign policy can be used to try and deter yet another war in the region.

scholarly journals Scour monitoring of a bridge pier through eigenfrequencies analysis

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Mohamed Belmokhtar ◽  
Franziska Schmidt ◽  
Alireza Ture Savadkoohi ◽  
Christophe Chevalier
Keyword(s):  
Soil Structure ◽  
Dynamic Behaviour ◽  
Dynamical Behaviour ◽  
Bridge Pier ◽  
Bernoulli Beam ◽  
Scour Monitoring ◽  
Innovative Method ◽  
Equivalent Length ◽  
Cantilevered Beam ◽  
Euler Bernoulli Beam

AbstractThis paper presents an innovative method for scour monitoring, based on the analysis of the dynamic response of a bridge pier embedded in the riverbed. Apart from the mechanical and physical characteristics of the pier itself, soil-structure interaction (SSI) has an impact on the dynamical behaviour of the system. This is particularly the case for eigenfrequencies of the pier which decrease when the free length increases. In this paper, analytical developments are carried out for an Euler–Bernoulli beam, modelling the pier which is embedded in the soil with Winkler springs for SSI. By using Hamilton’s principle and endowing the specific boundary conditions, the system frequencies are assessed by looking for roots of the characteristic equation of the system. These eigenfrequencies are then compared with those of an equivalent cantilevered beam, which can be expressed analytically. Moreover, experiments are carried out to validate the concept of equivalent length as a parameter of the inverse problem, linking the dynamic behaviour of the system and the embedded length.

scholarly journals Leidenfrost droplet trampolining

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Gustav Graeber ◽  
Kartik Regulagadda ◽  
Pascal Hodel ◽  
Christian Küttel ◽  
Dominic Landolf ◽  
...  
Keyword(s):  
Liquid Droplet ◽  
Bottom Surface ◽  
Pressure Oscillations ◽  
Experimental Conditions ◽  
Propulsion Mechanism ◽  
Leidenfrost Effect ◽  
Spontaneous Oscillations ◽  
Rigid Surfaces ◽  
Hot Surface

AbstractA liquid droplet dispensed over a sufficiently hot surface does not make contact but instead hovers on a cushion of its own self-generated vapor. Since its discovery in 1756, this so-called Leidenfrost effect has been intensively studied. Here we report a remarkable self-propulsion mechanism of Leidenfrost droplets against gravity, that we term Leidenfrost droplet trampolining. Leidenfrost droplets gently deposited on fully rigid surfaces experience self-induced spontaneous oscillations and start to gradually bounce from an initial resting altitude to increasing heights, thereby violating the traditionally accepted Leidenfrost equilibrium. We found that the continuously draining vapor cushion initiates and fuels Leidenfrost trampolining by inducing ripples on the droplet bottom surface, which translate into pressure oscillations and induce self-sustained periodic vertical droplet bouncing over a broad range of experimental conditions.

Scour problems at railway bridges on the Thompson River, B.C.

1980 ◽  
Vol 7 (2) ◽  
pp. 357-372 ◽  
Author(s):  
Charles R. Neill ◽  
L. Ralph Morris
Keyword(s):  
British Columbia ◽  
Thin Layer ◽  
Special Form ◽  
Local Scour ◽  
Main Line ◽  
Railway Bridges ◽  
Model Study ◽  
History Of ◽  
Scour Protection ◽  
Research And Design

The paper describes the history of riverbed changes and associated pier foundation problems at a series of five bridges along the Canadian National main line in the Thompson River valley of British Columbia. Pier failures were experienced in past years at two of these bridges, and there is a long history of placing rock riprap to combat local scour. The riverbed consists mainly of a thin layer of coarse alluvium overlying consolidated silt and clay.Special investigations conducted for one bridge, including a hydraulic model study, are described in some detail, and various schemes considered for foundation upgrading are outlined. Details are given of a special form of scour protection apron that was installed at one pier.Some research and design implications of the cases described are discussed briefly.

Dynamical behaviour of a torsional system with parametric and external excitations

2000 ◽  
Vol 214 (7) ◽  
pp. 955-973
Author(s):  
G Adiletta ◽  
A R Guido
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Behaviour ◽  
Asynchronous Motor ◽  
Dynamical Behaviour ◽  
Lumped Parameter ◽  
Mass Moment ◽  
Mass Moment Of Inertia ◽  
Torsional System ◽  
Parametric And External Excitations ◽  
Crank Mechanism

The dynamic behaviour of a torsional system with a one-cylinder, reciprocating compressor driven by an asynchronous motor is studied using a two degrees-of-freedom (2 DOF) lumped-parameter theoretical model. The model takes into account the variability of the mass moment of inertia of the crank mechanism and the presence of pressure forces loading the compressor piston. The influence of the ratio of the variable to the constant part of inertia in the crank mechanism and the effect of the load torque due to pressure forces acting on the piston are examined in relation to system dynamic behaviour. Experimental data, obtained with the adoption of a suitable rig, show that the theoretical indications can be considered reliable, despite the approximation that was given to the mathematical model as far as the treatment of the damping and the absence of clearances were concerned.

scholarly journals Composing instrument control dynamics

2002 ◽  
Vol 7 (3) ◽  
pp. 255-266 ◽  
Author(s):  
Dylan Menzies
Keyword(s):  
Dynamic Systems ◽  
Dynamic Control ◽  
Dynamical Behaviour ◽  
Control Parameters ◽  
Electronic Instrument ◽  
Interface Control ◽  
Control Stage ◽  
Acoustic Instruments ◽  
History Of ◽  
Instrument Control

The expression gestural mapping is well imbedded in the language of instrument designers, describing the function from interface control parameters to synthesis control parameters. This function is in most cases implicitly assumed to be instantaneous, so that at any time its output depends only on its input at that time. Here more general functions are considered, in which the output depends on the history of input, especially functions that behave like physical dynamic systems, such as a damped resonator. Acoustic instruments are rich in dynamical behaviour. Introducing dynamics at the control stage of an electronic instrument can help compensate for lack of dynamics in later non-physical synthesis stages. A broadening of the function space offers new aesthetic possibilities for composing instruments. Examples are presented to illustrate the new design/composition mode as well as practical techniques. In this context, it is suggested that the word mapping be updated with the more descriptive expression dynamic control processing.

scholarly journals The crackling sound of Leidenfrost stars

2018 ◽  
Vol 850 ◽  
pp. 1-4 ◽  
Author(s):  
P. Brunet
Keyword(s):  
Free Surface ◽  
Standing Wave ◽  
Pressure Fluctuations ◽  
Hot Plate ◽  
Liquid Drops ◽  
Boiling Crisis ◽  
Drop Dynamics ◽  
Leidenfrost Effect ◽  
Vapour Flux

Liquid drops deposited on a hot plate can experience a boiling crisis, when the vapour flux is strong enough to ensure the levitation of the drop and the relative insulation of the liquid from the solid. It is often denoted Leidenfrost effect, after the German Johann Gottlob Leidenfrost, who first reported it in 1756. While many studies have encompassed various applied issues associated with this phenomenon, aiming to control and prevent its appearance, Ma & Burton (J. Fluid Mech., vol. 846, 2018, pp. 263–291) focused on the spontaneous appearance of a standing wave at the free surface, together with temporal oscillations, making the drop adopt the shape of a star. Their far-reaching study presents exhaustive results using six different liquids with a range of different volumes and temperatures, in which they systematically extracted the drop dynamics together with the pressure fluctuations in the vapour cushion below.

Impact of Drops on Various Non-Wetting Surfaces

2009 ◽  
Author(s):  
Philippe Brunet ◽  
Alain Merlen
Keyword(s):  
Experimental Study ◽  
Contact Angle ◽  
Thin Layer ◽  
Initial Velocity ◽  
Liquid Drop ◽  
Spray Cooling ◽  
Lateral Extension ◽  
Hot Plate ◽  
Boiling Crisis ◽  
Leidenfrost Effect

We have carried out an experimental study of liquid drop impact on various superhydrophobic substrates. Our surfaces are of two kinds (1) a carpet of chemically coated nanowires and (2) a smooth warm substrate. In the latter case, the Leidenfrost effect (also called ‘boiling crisis’) ensures the existence of a thin layer of air coming from the evaporation of the drop, thus preventing the drop to touch the warm surface. Technically, in this latter situation the contact angle can then be considered as equal to 180 degrees, with no hysteresis. Due to its initial inertia, the drop experiences a flattening phase after it hits the surface, taking the shape of a pancake. Once it reaches its maximal lateral extension, the drop begins to retract and bounces back. We have extracted the lateral extension of the drop, and we propose a model that explains the trend. We find a limit initial velocity beyond which the drop (1) protrudes into the nanowire carpet (2) touches the hot plate, provoking a local violent boiling. We discuss the relevance of practical issues in terms of self-cleaning surfaces or spray-cooling.

scholarly journals VIII. Contributions towards the history of the colouring matters derived from coal-tar

1863 ◽  
Vol 12 ◽  
pp. 647-648 ◽  
Keyword(s):  
Boiling Point ◽  
Large Scale ◽  
Coal Tar ◽  
Fractional Distillation ◽  
Commercial Product ◽  
Previous Note ◽  
Starting Point ◽  
History Of

In a previous Note I have shown that the red colouring matter cannot be obtained from normal aniline by the action of the agents usually employed for the preparation of this colour on a large scale. This observation naturally induced me to seek for the constituent in the commercial aniline which gives rise to the formation of aniline-red. I have already remarked that the commercial product which is best suited for the manufacture of the red colour, boils at a temperature appreciably higher than the boiling-point of normal aniline. The idea presented itself of submitting this substance to a fractional distillation, or else of effecting a methodical separation of the hydrocarbons which constitute the starting-point for the manufacture of the bases; but, as is well known, these processes are difficult and tedious, and there is little chance of success unless the operation be performed on a very large scale.

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