What is Computational Fluid Dynamics?

In a recent post, Why you should use High-Speed Cameras for visualizing Fluid Mechanics’, we briefly discussed fluid mechanics and how the use of high-speed cameras helps in the development of the field. You can take a look at it here if you haven’t.

CFD

What is Computational Fluid Dynamics?

In this article, we’d like to discuss  another interesting topic: computational fluid dynamics, also referred to as CFD. This is the branch of fluid mechanics that deals with the solution of the governing equations of fluid dynamics using computers [1].

As mentioned in our Fluid Dynamics Blog (link to the blog), fluid mechanics has a robust theoretical foundation. However, the equations that describe the motion of fluids, the Navier-Stokes (NS) equations, are difficult to treat analytically. There are a few exact solutions, albeit for highly idealized situations. Due to this, they only sometimes correspond to cases of practical relevance. Yet, they are useful as a benchmark to evaluate the performance of models that solve the NS equation numerically.

The advent of powerful computers enabled researchers to treat sets of differential equations as a set of algebraic equations that could provide solutions that otherwise would not be possible to obtain. With the development of faster and more compact computers, the field of CFD grew as well. Nowadays, corporations as well as research facilities make use of CFD as part of their R&D activities. Individuals willing to analyze relatively simple cases can do so in a personal computer. The subject is also taught in a large number of universities around the world, with the leading universities exposing their students to work in cutting-edge projects, thus significantly enhancing their academic background. 

CFD

What fields use Computational Fluid Dynamics? 

CFD has been applied to a large number of fields i.e., weather prediction[2], turbomachinery design[3], aerodynamics[4], combustion[5], aerospace[6], medicine[7], and food processing[8], to name a few. Recently, the complex features present in the flight of a hummingbird have been simulated by Ren et al. (2016)[9]. The authors point out that this type of work is crucial to get a deeper understanding of the complex wing-body interaction of different insects and birds and their flight mechanisms for maneuvering. Also, the results of this type of study can be useful to design and improve the performance of the next-generation micro aerial vehicles.

Recent videos captured by Christian Sasse using a Chronos high-speed camera also portray the complex maneuvers performed by these tiny creatures[10,11]. The wings of insects induce a flow in their vicinity that can be used to confuse their prey, as can be seen in the video shown here below. The flow created by the flapping of the insect’s wings cannot be seen yet its effect can be certainly felt. 

In summary, in the present blog, we want to highlight how the combination of high-speed video footage and data provided by CFD can significantly enhance our understanding of processes that otherwise would not be easy to clarify. Also, it can lead to bioinspired products of higher performance than those currently available to the public.

If you are interested in the topic you may take a look at a few popular textbooks on CFD listed in the References section[12, 13, 14, 15]. The literature on CFD is quite vast, thus here we present only a very small sample.

References

1. Boris, J.P., 1989. New directions in computational fluid dynamics. Annual review of fluid mechanics, 21(1), pp.345-385.
2. Castorrini, A., Gentile, S., Geraldi, E. and Bonfiglioli, A., 2023. Investigations on offshore wind turbine inflow modelling using numerical weather prediction coupled with local-scale computational fluid dynamics. Renewable and Sustainable Energy Reviews, 171, p.113008.
3. Pinto, R.N., Afzal, A., D’Souza, L.V., Ansari, Z. and Mohammed Samee, A., 2017. Computational fluid dynamics in turbomachinery: a review of state of the art. Archives of Computational Methods in Engineering, 24(3), pp.467-479.
4. Schetz, J.A., 2001. Aerodynamics of high-speed trains. Annual Review of fluid mechanics, 33(1), pp.371-414.
5. Tieszen, S.R., 2001. On the fluid mechanics of fires. Annual review of fluid mechanics, 33(1), pp.67-92.
6. Ivanov, M.S. and Gimelshein, S., 1998. Computational hypersonic rarefied flows. Annual Review of Fluid Mechanics, 30(1), pp.469-505.
7. Yoganathan, A.P., He, Z. and Casey Jones, S., 2004. Fluid mechanics of heart valves. Annu. Rev. Biomed. Eng., 6, pp.331-362.
8. Xia, B. and Sun, D.W., 2002. Applications of computational fluid dynamics (CFD) in the food industry: a review. Computers and electronics in agriculture, 34(1-3), pp.5-24.
9. Ren, Y., Dong, H., Deng, X. and Tobalske, B., 2016. Turning on a dime: Asymmetric vortex formation in hummingbird maneuvering flight. Physical Review Fluids, 1(5), p.050511. DOI: https://doi.org/10.1103/APS.DFD.2015.GFM.V0088
10. [Christian Sasse/SassePhoto]. (2023, June 8). Hummingbird in full glory- super slow motion [Video]. Youtube. https://www.youtube.com/watch?v=1G9zem9rhao
11. [Christian Sasse/SassePhoto]. (2023, June 26). Hummingbird Tongue in insane detail [Video]. Youtube. https://www.youtube.com/watch?v=YFcL5Qihd5U
12. Anderson, D., Tannehill, J.C. and Pletcher, R.H., 2016. Computational fluid mechanics and heat transfer. Taylor & Francis.
13. Versteeg, H.K. and Malalasekera, W., 1995. Computational fluid dynamics. The finite volume method, pp.1-26.
14. Biringen, S. and Chow, C.Y., 2011. An introduction to computational fluid mechanics by example. John Wiley & Sons.
15. Pozrikidis, C., 2016. Fluid dynamics: theory, computation, and numerical simulation. Springer.