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Modelling turbulent fluid-, thermo-, and droplet dynamics in the Leipzig Aerosol Cloud Interaction Simulator (LACIS-T)

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all but come to my talk it's known a bit more applied see if d is not so much in theory as this is a ball simulation of to the floor and the public dynamics and
the fact is he also called and action simulator many if you might have seen it yesterday my name's apples and consultant I was the other guy who gave to
this as presentations yesterday and we work together with single Meyer and and of course this 1st of OK does a self-signed
1st I give a short introduction to the topic and I talk about the food and thermodynamics inside the wind tunnel it's point is about a and topic dynamics and finally I give some conclusions in the novel but at 1st for the introduction and the book tells you all know colds right and you all know that they play you which will in long term climate and truck term rather predictions so be sure to really investigate all data unfortunately this is hard because sale transcend their tervalent intermittent inhomogeneous and they cover a wide
range of spatial and temporal scales as you can see here this some of you we are out in places the dealing with this site the you have a look at the micro physics how do I felt condensation of the activate Excel Toeplitz how do day after they have activated to these problems and how the mixing of different flows contributes to this of course cluster in much larger scales for example entrainment in this case of 100 meters Sulston the health status of multiple tens of skew meters and finally you have covered almost all continents with clubs so additionally day are hard to reach because they're up in the skies on where you can use planes but and they're not reproducible for example
so as adults how to reach users thought it might be a good idea to get
them to us when we set up this of laboratory to have producing the conditions to
investigate the cult and developments also
usually formed by water vapor which condenses the not condensation of the East Sea Sea ends can be maybe for example past as we have seen yesterday in a talk by Robert Bachman they can also be made of 2 carbon from industry accompanied by incomplete combustion volcanoes emits sulfates which act as easy and even free to Tonkin actors condensation of the and the deal was salt which may be you of lifted up from see what these condensation of the size ranges of approximately 100 meters some less some more and the condensation and this and the key is mainly defined by the material properties of particle properties like diametre and and can physical properties and here especially the temperature and the water vapor content of places he is now designed to investigate how how much too turbulent fluctuations of cues on the ends of properties influenza particle and topic microphysics some words
about this is the this short fraudulent like the
shells will contradictions were later you see a schematic here it's a close to printing and type and tunnel on the floor directions clockwise here features to conscious each with up to 5 thousand just permanent of flow speed has and he can precisely define the thermodynamic and flow conditions in both of these branches as independent from each other so the principle is that we have play here which supplies warm and my air which is stand accelerated by 2 players for 1 for each branch there's let's through photos to get particle-free at 1st the air can then be humidified to those defined 2 point and after lost his humidify there's a to heat exchangers with with which are coupled with thermostats which set them humidified air to as defined temperature and then here to progess are mixed and sold can reach for example suppose supersaturated states in our measurement section and additionally here in this point is 2 point as next weekend in checked in well defined particles disorders fault condensation increase at the moment to use salt particles has already set and these the former cloud inside this mess and measurement section now this talk is about the question if we are able to simulate the flow the thermodynamics and apart and behavior inside this 1 time Dutch
there's the not so good to see video of the polis was taken from the initial price at nominal they made some ice cream use of this quite fast but there's so so here you can see how this terrible and motions the influence of clouds forming and of development Our country of fluid and
thermodynamics and at 1st principal things to investigate these the influence of the turbulence on them might microphysics we need of course feuds for instantaneous mean and would mean square values and measurements usually don't give of enough information about all these quantities at once we usually you have point Proc so it can measure along the line but you you don't get the old feud inside so this is why we need the simulations and the need for for exact knowledge of the thermodynamic conditions inside the core of the René tunnel before we can simulate the particles and and the top attack duration and this means velocity and turbulence temperature and humidity if you read about the measurement techniques
for the floor this is the measurement section in detail that's 2 meters high 80 centimeters wide and 20 centimeters and in depth at the coordinate system has its origin here at the so that of the Y axis being here in the short directions the excesses the long direction this will be used for a lot of presentation and views . talks for measurements hot wire for velocity in court fire for temperature and they're usually then moved along lines in the Y direction here 1 1 twin 20 30 centimeters below there was all in that so we do high frequency measurements approximately 3 kilohertz so that we can gets when Allen analysis to different quantities which means and means and fluctuations OK for the numerical
methods use open form resolve the transient incompressible Navier-Stokes equations for some examples you apply them blood in which allows for larger time steps than peaceful perspectives most often performed for this example it's you was business approximations almost for temperature simulation and is just treated as passive scalar use second-order schemes for almost everything that these exceptions and the Consulate events with large eddy simulation what which is called dynamic a creation of the because created 2 comma decimal 5 seconds of through time but the statistics to compare with the measurements was only done for put the time after you point 5 seconds traffic was a to the main anabolic conditions of course we don't model all oftentimes we don't need a wire and the Flores and so on so we have
on measure 1 of this section here this is executive mesh with approximately 7 comma decimal 5 billion sense this is not the actual we only to some which refinement and the walls we have additional refinement here at want to go in there and so on here's to name monger conditions here in
that's begins set fixed velocity temperature and humidity the and the outlets with fixed pressure here you can see a intervalence could which into it uses some artificial turbulence inside of flow and then the form and that use some psychic bonded this is 1st
results from left to right for the instantaneous velocity of mean velocity for determine fluctuations in the would mean stress of the dual fluctuations in this is done for tool different plants this explains the different values here I want planes directly below evolve to troubles with the other planes and at between 2 parts of history and as you can see from in the beginning velocity awards and finally you these mean values reach some across city states you can see here the most turbulent fluctuations we have in our channel and also these fluctuations which of clauses city state after some time here's the comparison with the
of measurements along these lines I mentioned earlier this for its and axis you have to white for in it and the the Y axis you have to velocity I think 3 at the measurement results quite good for example the can creating need the see in the middle so I think you get to floor and here you see some visualization of determined structures we have in our internal is done with the Q isosurfaces which just the 2nd in life and of 2 gradient of of velocity and from the beginning and you can see the structures see loving your own watched from terrible script and then slowly decreasing I don't want to know which we compare this to all measurements with the turbulence intensity which is the ratio of 2 to 1 fluctuation which means mean velocity actually is just for 2 components because of the of the hot-wire measures only 2 components of 2 moles of the CD results for this year
mostly I think we need the results quite good but even so leave or overestimated trouble and so that but all I think this result looks quite then for the
temperature and this is an example of every have
warm and cold air mixing this is a snapshot of the simulation here of 23 decrease on the left side 13 decrease on the white side you have of what's with a certain temperature and you hear from 2 and mixing zone so this is now compact and by means of the mean temperature which is made relative with makes on minimum value so they see what you for minimum temperature and maximize ship the maximum value for this 1 and here you can see that the also it's these results quite good but again for the chairwoman properties there's some overestimation you last thing for the and
thermodynamics assume at be treated humidity here as a passive scalar purchased transported to the floor and combined with the temperature we get a relative of humidity you can see here
and this is another interesting thing if you have here so relative humidity of approximately 50 in the left side and here of approximately 70 per cent of the light side about the half year some of some over some higher situation so up to 75 per cent is ready there would mixing might play a role which might lead to faster on top with activation for example as I said earlier this is what you want to investigate the following for the particle and topic
dynamics at 1st again some words about a measurement technique have the use of Whitesides particle spectrometer from Perlis it's called the analysis and the have 2 different measurement hates depending on the case we want to investigate 1 is 10 centimeters the other 1 25 centimeters below the aerosol and that the injured particles that follow the flow down there and then they start to absorb water vapor they start to quote to shrink depending on the physical properties and surroundings and then we measure the particle diameters your here for 20 minutes and from this we get the popular Zisis solution for momentum of measurements OK now for the numerical methods news that origin particle tracking which tracks individual particles through the flow field follow you have to assume that they're point must particles we need models for the interaction of the carrier fluid other particles views about your own leader and actions with the care of weakness well man usually as usually dare approximated as spheres which makes things a lot easier the particle size of has to be was a lot smaller than the control room size and usually you you need field used to describe particle behavior the tension position is defined by the velocity change of velocity is defined by the some of the forces acting on the party this and you can also a calculator quotation of the products but being neglected year this might not play will the models we used to forces acting on the part of this year's chest the track force have thing EDS's neglected additional models of course we have an injection model defining the particle position size by major velocity and on we course last answer model which come defines how much whatever the part get from the gas phase which is mainly driven from the gradient between the surface right situation at the particle surface and the saturation and ambient there
OK this is some sporadic OFTA's of things you have to score a little luck function for the course model is the date of the need for both model will therefore we data of particle data model data of which is on the need for the portion the might not be so for the moment you on the thing which is interesting is that we have the largest time sets foot on a looped and the have subgroups for the Lagrangian tuneup and inside these subgroups if again subgroups for the modernist as it quite still quite circulation and bonding
conditions I use the same domain as before now I'm the only differences and dissolve lot compressible Navier-Stokes equations are solved the thing I just the same and we consider 2 cases here with phi and we do a lot of humidity as particles we use sodium chloride as in the experiments they have a diameter of 320 nominators also measure matches experiments of of course ejected at of particle in that attract for is your point 5 seconds which is just the time they need whether widow measurement section find model and the subprime time steps were like origin tracking and the course model are chosen by the Kelly for the Departed required numbers below 0 comma decimal 5 and must change is not more than 20 per cent of the particle mass for 1 both models something
OK so we can come to Edo results for this
1st cases this with relative humidity at the site you see this relative humidity here the temperature you can see the white male comparatively low of relative humidity from aerosol in that so the particles are injected here with this VN 29 emitters by meter which is the which promised and they start to relative humidity increases so they this reddish color here and so on we are able to reproduce this behavior that they start to call and direct so plot the relative humidity is high enough so this is the end of the year evaluated here at this
position similar to our measurements and you can see here particle size distribution of pirated at the bottom and the relative frequency here at the left side and a left axis measure the simulated diary does not completely off but it's that law and what really we can see rate could a set of simulations predictive really narrow this solution why the measurements show that there are even of today have comparative people pirated why is this we do not know at the moment and maybe we do not really meet Obama conditions we have in the container maybe also not have enough time for the for some meaningful statistics in our simulations maybe also the sockets scale turbulence might play a world which was neglected phone also dismayed also dispersed apart it's a bit more but we have not implemented a model for this year in the 2nd
case for the device humidity and then on
the left side you have this community temperature know the party the in that flow has a comparatively high humidity so that the particles start calling it the beginning and then again they tend to shrink as here you can see in this terrible implications on the humidity's mixing every comes wire this is also compared to
measurements he had a part in it's quite good I think but still the distribution as well differently to know all of this might be for the same reasons as before about at these the diameter looks a bit better here this brings to
things into summary and outlook 1st for the summary on simulated to flow and thermodynamics inside is is the the thought and simulations and of form where the results agree quite well with the measurements we implemented departing quotes modeling of forms the French a model of so the 1st simulations were quite but I think for 1st short Of course as some room for improvement and for the outlook so I mentioned to you want to implement a separate scale turbulence dispersion for the particles and if you want to do further simulations for other conditions for longer times and on you want to do more measurements for example also the low regions often the measurement section which was not mentioned get and in the long term of course you want to see some correlations between turbulence and the public particle behavior in addition we also want to do some improvements and places the find something insulation and sealing to get the boundary conditions of it at the end we also want to improve on particle measurement OK then thank you for listening and open for you press and if
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Metadaten

Formale Metadaten

Titel Modelling turbulent fluid-, thermo-, and droplet dynamics in the Leipzig Aerosol Cloud Interaction Simulator (LACIS-T)
Serientitel The Leibniz "Mathematical Modeling and Simulation" (MMS) Days 2018
Autor Schmalfuß, Silvio
Mitwirkende Leibniz-Institut für Oberflächenmodifizierung e.V. (IOP)
Leibniz-Institut für Troposphärenforschung (TROPOS)
Lizenz CC-Namensnennung - keine kommerzielle Nutzung - Weitergabe unter gleichen Bedingungen 3.0 Deutschland:
Sie dürfen das Werk bzw. den Inhalt zu jedem legalen und nicht-kommerziellen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen und das Werk bzw. diesen Inhalt auch in veränderter Form nur unter den Bedingungen dieser Lizenz weitergeben.
DOI 10.5446/35354
Herausgeber Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB)
Erscheinungsjahr 2018
Sprache Englisch
Produktionsort Leipzig

Inhaltliche Metadaten

Fachgebiet Informatik, Mathematik
Abstract The turbulent Leipzig Aerosol Cloud Interaction Simulator (LACIS-T) is a Göttingen-type moist-air wind tunnel designed for investigating interactions between turbulence and cloud microphysics under reproducible and well defined thermo- and fluid dynamic conditions. To draw reliable conclusions from measurements at the wind tunnel it is necessary to have precise knowledge about the flow field and turbulent fluctuations of velocity, temperature, and water vapour concentration. For this reason, the flow inside the measurement section of LACIS-T is simulated with OpenFOAM, employing a Large Eddy Simulation model for turbulence. Different boundary conditions for water vapour concentration and temperature are considered and the results are compared to measurements. Furthermore, particles are tracked through the domain using a Lagrangian approach. Thereto, a suitable growth model is implemented to calculate particle/droplet growth due to the condensation of water vapour from the gas phase. Joint work with D. Niedermeier, J. Voigtländer, and F. Stratmann.

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