Achievements of an Iranian Researcher in Germany in Marine Biology

Professor Arzhang Khalili at the Max Planck Institute in Bremen is engaged in research in the field of fluid hydrodynamics with applications in ocean biology. He has made innovative achievements in solving the Stokes paradox.

Claude-Louis Navier and Sir George Gabriel Stokes independently introduced very important equations in the early nineteenth century that can be used to calculate the velocity field and pressure field resulting from the motion of liquid and gas particles (fluids). Today, these equations have extensive applications in engineering and natural sciences.

In 1851, Gabriel Stokes succeeded in presenting a simpler equation to describe the very slow motion of fluid particles. Through this equation, Stokes was able to calculate the drag coefficient of spherical objects moving in a fluid, but failed to calculate the drag coefficient of cylindrical objects, and research reached a standstill at this point. From 1851 onwards, this issue captured the attention of fluid dynamics scientists, and all tried to provide a solution to this problem. However, the answers obtained from calculating the drag coefficient of cylindrical objects were different. For this reason, this impasse became known as the Stokes paradox and remained unsolved.

The question that arose for Professor Khalili was how much organic or organic material microscopic living organisms in ocean waters bring with them from the surface to the ocean floor during their descent. After solving the issue with the help of mathematics and numbers, experiments were needed to validate these calculations, since there is a high probability of error in numerical mathematics.

Professor Khalili, in an effort to find the cause of these differences, realized that the diversity of the results obtained was actually due to different experimental conditions.

Professor Khalili explains in this regard: “The deep waters of the oceans play a very effective role in the ecology and climate conditions of the Earth. At the surface of oceans and deep seas, there are countless tiny organisms and particles. When sunlight shines on these particles, photosynthesis occurs and the process of biological absorption and release takes place. These particles are the result of a combination of diatoms, phytoplankton, fecal pellets, and dust from storms, etc. Once the specific weight of these particles becomes heavier than the specific weight of water, they slowly move downward (to the ocean floor). These particles, which are called marine snow, contain organic materials that gradually and slowly reach the ocean floor and transfer life from top to bottom. Microbes settle on these diatoms and phytoplankton and begin to respire, and as a result, carbon dioxide is produced. This carbon dioxide, due to its lightness, traverses the entire path from the ocean floor back to the surface and exits the waters, causing many problems including global warming, creating holes in the ozone layer, and melting polar ice. This issue causes disruption in global ocean carbon circulation and creates problems and changes in climate and weather conditions.”

These changes can be predicted to some extent through computer programs, including a program currently used at the Meteorological Institute of the Max Planck Scientific Institute in Hamburg. These programs are capable of simulating the state of the Earth thousands or hundreds of thousands of years in the future and predicting its climate conditions.

One of the input data for these computer programs is the amount of organic or carbon materials entering the ocean’s interior from its surface, since these materials produce carbon dioxide in the next cycle. Since the particles of green algae and diatoms are cylindrical in shape, Professor Khalili’s achievements in solving the Stokes paradox have made it possible to improve some of the input data of these programs and obtain a relatively more accurate estimate of the amount of carbon or organic materials that can reach the sea surface.

Continuing the conversation, Professor Khalili emphasized the importance of learning from the operational strategies and life of living organisms in the oceans: “For example, some microorganisms produce proteins that, in combination with the salt water of the oceans, create a natural adhesive. In the future, this adhesive could replace stitches in surgical operations.”

Another research topic that Professor Khalili is currently engaged in is examining the collision of fluid particles instead of using equations of motion to calculate the velocity field and pressure field of the fluid. This research simplifies difficult hydrodynamic calculations and reduces computer computation time by converting nonlinear equations to linear ones.

Source: DW