Tobias Holzmann & Holzmann CFD

For those who are interested about the backgrounds of Tobias Holzmann and Holzmann CFD, this secion gives insight into that topic

First Contact with OpenFOAM®

Tobias Holzmann got in contact with OpenFOAM® during his practical semester (Bachelor study at the Fachhochschule Augsburg, German) in 2009 at the company Emcon Technologies in Augsburg (nowadays named Faurecia). He was working in the R&D department investigating thermal-electrical generator modules (TEG). The focus of the work was creating a test device to verify the effectiveness of the TEG modules given in the supplier's datasheet.

— The test device is given in the image right —

However, during all measurements, the effectiveness of the TEG modules was always lower than the values mentioned in the supplier's datasheet. During that time, a colleague named Dr. Christoph Hosfeld was working with the latest OpenFOAM® release 1.7.x and the conjugated heat transfer solver. In short, he investigated the test device. He showed heat-flux concentrations inside the copper blocks, which was a result of the dimensionally large heating and cooling block compared to the copper blocks.

— The numerical analysis lead to an optimization of the test device —

To resolve this issue, two concentration blocks were added to the test setup. In doing so, the temperature distribution right at the beginning of the first calibration block was much more homogeneous. Thus, the heat flux was more uniform, and at the end, the measured temperature inside the calibration blocks.

— A comparison of the test devices is given in the video —

Note: The video does not represent the test device dimensions in real and also does not contain the correct physical values. It is just a demonstration of how computational fluid dynamics influenced Tobias's work in the test-bed in the year 2009.

This was the first time Tobias got in contact with the open-source software toolbox OpenFOAM® and got a feeling of how CFD can give insight into problems and phenomena.

TEG test device
Distribution before and after the optimization

Tobias first steps with OpenFOAM® and his CFD career

As always, different circumstances lead to OpenFOAM®. Tobias intended to write his Bachelor thesis about the new generation of thermal-electrical generator modules. The topic was already submitted to the Fachhochschule Augsburg, and the work already began. However, the TEG modules that should be investigated were never delivered. Thus, Tobias had to decide to skip the topic and study into another one. As time was already narrow, his professor, Dr. Markus Reppich, suggested investigating heat transfer problems using CFD tools.

— The open source toolbox for computational fluid dynamics —

Following the suggestion of his professor, Tobias decided to use OpenFOAM® for his Bachelor thesis and the investigations. The start was hard, as the new operating system Linux (Ubuntu) and OpenFOAM® were utterly new. A lot of studies were performed to understand how the toolbox works and how different physical phenomena can be achieved. During that time, Tobias frequently asked questions on the German OpenFOAM® forum Here, Thomas Tian was almost his mentor as he was the moderator of the forum during these days. 

— The OpenFOAM toolbox was challenging and frustrating as well as beautiful —

After Tobias finished his Bachelor thesis, he applied for the Master's degree at the Fachhochschule Augsburg. Here, new lectures such as »Numerical Simulations» and other computational fluid dynamic related topics were fascinating to him. At the Fachhochschule Augsburg, the commercial software ANSYS CFX® was used. All investigations that were performed using the commercial software were re-investigated by using OpenFOAM®. 

— The Results of ANSYS CFX® and OpenFOAM® were always identical —

During the Master study, Tobias investigated a variety of different simulations. However, mostly without knowing too much about the background of numeric's, code implementation, discretization schemes, mesh parameters, the solved equations, physics, and so on. The breakthrough in terms of OpenFOAM®, understanding the code, and programming came during his Master thesis, which was written at the BOSCH AG company in Lollar (Germany). The topic of investigation was bio-mass combustion chambers using OpenFOAM® and the steady-state laminar flamelet model; the model was built for OpenFOAM® 2.1.0 and published by the CRECK modeling group from Milano (Italy). At the end of his Master thesis, his professor, Prof. Dr. Alexandra Jördening, mentioned that he set a new reference level of mathematics at the Fachhochschule Augsburg.

— The flamelet model for OpenFOAM® is still kept up-to-date —

Certificate of Bachelor of Engineering
Certificate of Master of Engineering

After the success achieved Master study, Tobias worked as a test-bed engineer for the company FAKT GmbH in Heimertingen, Germany. On the test-beds, the following investigations were performed: hot-shake catalysts tests, hot-shake diesel particle filters (DPF) tests, and thermo-shocks for catalysts and DPF's. Furthermore, FAKT developed gas-burner for test-beds. Thus, Tobias investigated into different parts of the combustion chamber numerically (side projects). Also, the whole test-bed construction, measurement installation, and set-up were performed by him.

— Tobias did not work in the field of computational fluid dynamics but he was still active on forums —

— During the year 2013 he started to create his website »Holzmann CFD« to collect the information for the community —

In the year 2014, Tobias decided to take the opportunity of a vacant Ph.D. position at the Montanuniversität Leoben. From 2014 to 2018, he investigated a lot in computational fluid dynamic topics, mathematical expressions, equations, derivations, matrix algebra, and much more, which lead to the well-known book named »Mathematics, Numerics, Derivations and OpenFOAM«. His colleagues, especially Dr. Alexander Vakhrushev and Dr. Jan Bohacek, inspired him, and they had a lot of intensive discussions about numerical simulations. During that period, Tobias' activity in the forum reached his maximum impact. In the year 2018, Tobias Holzmann completed his Ph.D. study with »Auszeichnung« (kind of summa cum laude) and went back to Germany.

— Tobias published his knowledge on his website for the community, thereunder screencasts, OpenFOAM® tutorials, developments and publications —

Since September 2018, he is working for MAN Energy Solutions as a »Project Development and Tender Support« engineer without doing many numerical investigations. However, his ambitions are clear: Full-time job in the field of computational fluid dynamics.

Certificate of Doktor der Montanistischen Wissenschaften

As Tobias is not working in the fluid dynamic sector since September 2018 anymore, he focused more on his company Holzmann CFD. Hence, he decided to make different materials commercial (paid download) and changed the website into the community and commercial part. Furthermore, the site moved from to as a result of search engine optimization. Since 2018, Tobias supported companies regarding OpenFOAM® (training courses), software developments, and made quality reports of investigated numerical OpenFOAM® cases.

— Different companies and the related investigations are presented in the »Reference« section —

In 2020, Tobias decided to re-organize the website and re-update most of the material as an outcome of a dramatic private change. The material provided at his site should be kept free for-ever except for his book while hoping that people will support his work on free donations.  

Moderator on

Moderator on

As Tobias was a frequent user on and actively using OpenFOAM®, while growing his knowledge in  this field intensively, Thomas Tian asked him to become the moderator of the German OpenFOAM® forum. Therefore, since 2011, Tobias is the moderator of the German OpenFOAM® community forum and probably one of five frequent users who support people there.

— As moderator he gets informed about new threads —

Most questions were unresolved before Tobias started to support people on This changed since Tobias is trying to help all people to resolve their problem.

Tobias studied more and more complex subjects, and as the German OpenFOAM® forum did not provide sufficient support, Tobias went active in the well-known forum. In the beginning, Tobias asked a lot of questions (probably stupid ones too) but also tried to support other people around the forum. Somewhen in the year 2014, Jonas invited him to become a moderator on the forum, as Tobias was highly active. Since that, he is an official moderator, asking »mostly« high-level questions and supporting people.

— Top voted post: divDevRhoREff() function

Tobias commitment to support people on was drastically reduced since he finished his doctoral degree at the Montanuniversität Leoben (Austria) as time is a limiting factor since that.

What is Holzmann CFD and what is it not

— What it is —

Tobias Holzmann invented Holzmann CFD to publish his ideas, outcomes, and material at his place. However, Holzmann CFD became much more than just sharing the work of Tobias. It provides helpful content concerning OpenFOAM®. Free available training videos, screencasts, cases, publications, developments, and extensions, as well as many fun simulations, are ready to use and watch for people all over the world. The website is created primarily for the OpenFOAM® community. It is a place in which Tobias shows the capabilities and flexibility of the open-source software OpenFOAM®. Holzmann CFD provides libraries and applications, removes bugs, and contributes to the OpenFOAM Foundation version. Holzmann CFD further is a registered company in Germany managed by Tobias Holzmann with the intension to support companies with their individual need for OpenFOAM®. Tobias Holzmann tries to keep the level of simulations for his costumers at a decent and sustainable level. Tobias has a personal credo not to manipulate any numerical data, plot, or other things related to the computational fluid dynamics within a fair price.

— What it is not —

Holzmann CFD is a single person company, and thus, no one is employed. Holzmann CFD does not support ANSYS® products. Tobias Holzmann works with the people from the OpenFOAM Foundation. Also, he uses the version published by the OpenFOAM Foundation and therefore is not familiar with the extended project or the published ESI version too much. Holzmann CFD does not provide free personal support (only on public forums). Tobias Holzmann owns Holzmann CFD, but he is not working in full time as he is employed.