CFD reveals the sweet spot of Christmas markets

By Simon Fischer

Bratwurst. Lebkuchen. Glühwein. Bratwurst. Lebkuchen. Glühwein. Bratwurst. Lebkuchen. Carrousel. Glühwein….

Christkindlmarkt for beginners

Should you ever visit my hometown in the weeks before Christmas, you will know what I am talking about. Nuremberg, Germany, features one of the world’s oldest and largest Christmas Markets: The Nürnberger Christkindlmarkt. And so every year, millions of tourists come to stroll through the beautiful streets of Nürnberg old town, visit the castle, touch the golden ring at the beautiful fountain, to then enjoy some Nürnberger Bratwurst, followed by some Nürnberger Lebkuchen and flush it all down with a bunch of Nürnberger Glühweins. (We invented a lot of good stuff here in Nürnberg)

Christkindlmarkt for pros

Guess what, even though I am a local and one might think I would be fed up with this annual spectacle – I am not. I am actually no different. At least I was not until this year… And so, following the same tradition as last year, I went downtown, had a Bratwurst followed by a Lebkuchen and flushed it down with some Glühweins. But one thing was different this year: While I inhaled the usual lineup of flavors in their usual sequence I had this crazy idea: Come on, you have been doing this for years, you are a homie here, a professional Christmas Market visitor, you should step up your game.

For the ultimate Christmas Market experience, you cannot simply follow the mainstream and suck in those flavors in serial. For the ultimate experience you must find the sweet spot on this market. The place of maximum joy, the one where the smell of Bratwurst, Lebkuchen and Glühwein meet and cumulate to the ultimate blend of Christmas flavor.

(Not) finding the sweet spot with trial and error

Once the thought was in my head, it would not let me rest, I ran the streets up and down, passed by the Bratwurst stand, the Lebkuchen stand, had a Glühwein, went on, kept my nose up to suck it all in to identify that one place where it all came together. Nope not here, I thought, had another Glühwein, checked the next row. Bratwurst met Glühwein, but no sweet smell. At least a Feuerzangenbowle. Let’s have one. I went on. A lot of sweets in the air around the next corner but the wind was not ideal so the Bratwurst and Glühwein flavors went the other direction… I grabbed some cotton candy for a more diverse diet, and went back – to have another Glühwein. I was about to give up. You cannot find the sweet spot of a Christkindl market with trial and error I thought, took another quick cup and watched the Bratwurst smoke rise into the sky meeting some snowflakes on their way down… And as I stared at the smoke I knew the answer!

CFD – I thought – joy to the flow!

CFD is the answer. A digital twin needs to be born. Of the Christmas Market. One with Bratwurst, Lebkuchen and Glühwein… I had a quick Glühwein (and another 3 im Weggla) and headed home to my computer…

A sleepless holy night later the first of it’s kind…

CFD based sweet spot predictor for Christmas markets

Bratwurst, Lebkuchen and Glühwein fragrance distribution in top view.

was born. It has all it takes to simulate any real Christmas market and find the best spot there: Bratwurst, Glühwein and sweets flavors are released by the respective stands and their time dependent flavor distribution can be predicted for any given wind condition taking into account convective and diffusive transport on any given terrain and Christmas Market layout. (Admittedly the geometry at hand is a bit of a demonstrator prototype at this point ;-))

Bratwurst, Lebkuchen and Glühwein smell distribution in top view.

To identify the sweet spot for the expert visitor it is obviously important to asses the flavor distribution at the height of the visitors nose:

Bratwurst, Lebkuchen and Glühwein smell distribution at the height of the average adult human nose.

But – as we already learned – the ultimate experience does not stem from a serial absorption of the individual smells. The true expert knows that an explosion of emotion results from the multiplication of the individual smell experiences.

Christmas Market Smell Experience := Smell (Bratwurst(x,y,z_nose)) * Smell (Sweets(x,y,z_nose) * Smell (Glühwein(x,y,z_nose)))

and consequently the place to be P_maxiumum_joy is the associated location where

P_maxiumum_joy := MAX(Christmas Market Smell Experience (x,y,z_nose))

And so all it takes is a bit of the almighty Simcenter STAR-CCM+ CFD software and some smart post-processing to identify the ultimate sweet spot where the glorious experience of Bratwurst meeting Lebkuchen meeting Glühwein maximizes the joy of every Christmas market visit.

The place of maximum Christmas Market joy is located where Bratwurst meets Lebkuchen and Glühwein smell and it all multiplies to the maximum flavor explosion experience.

Gone is the need to walk around aimlessly, making your way randomly through throngs of people. Just simulate, identify, go downtown, buy a Bratwurst, buy a Ginger Bread, buy a Glühwein, then go to the targeted sweet spot and enjoy the ultimate Christmas market experience!

The first digital twin for finding the sweet spot on every Christmas market was born. Flowly Night, allerseits.

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This article first appeared on the Siemens Digital Industries Software blog at