Flow at Alfa Laval - a trainee's report

Karl Blomberg is one of Lighthouse trainees this year, read about his meeting with Stokes' law and how a equation about about dynamics can be of importance for any company.

In a true engineering spirit, this article about my initial time as Lighthouse trainee is preceded by the introduction of an equation:

My name is Karl Blomberg and to me this equation is a thing of beauty. My relationship to it began in October when I stepped through the entrance of the Alfa Laval office building in Stockholm, marking the start of my traineeship. The historic importance of the formula was apparent, it is engraved in the building exterior. 

During the weeks to follow, my relationship with the equation grew as I explored Alfa Laval’s technology and way of business. When moving on to the next company in the Lighthouse sphere the equation remains etched in my memory. It is commonly denoted Stokes’ Law and is a simplification of the generally insolvable differential equations that are central to a naval architect, but instead of describing significant resistance and complicated dynamics of a ship’s hull moving through water and waves, Stokes’ Law is about tiny particles in a viscous fluid. The formula describes the speed the particles would reach if they were allowed to fall freely through the fluid, or how quickly particles would settle.  This is a property made use of in the separators developed by Alfa Laval, with the difference that particle acceleration (variable g in the equation above) is considerably increased due to rotation.  

Although the formula is a simplification of advanced dynamics, it is as important now as it was 133 years ago, when the Swedish inventor and engineer Gustaf de Laval began selling his proprietary separators and thus laid the foundation for Alfa Laval. Back then it was about separating cream from milk, today applications are vast. One area of importance is solid residues from oil refining processes that are increasingly present in bunker fuel burned by the world’s merchant fleet. The existence of these hard, microscopic particles is a growing problem due to their potential to cause major damage to ship’s engines. The essential goal, now as then, is to maximize the left hand side of Stokes’ Law. 

When I first got acquainted with Stokes’ Law, my perception of Alfa Laval was based on scarce sources. As I move on to the next company in the trainee program I have grown an understanding of the company products, challenges and business methods. I have gained insight into the maritime industry and expanded my network within it. From day one, I have been given great confidence in taking responsibility for parts of projects in the forefront of trade technology. Tasks have varied from sales support to evaluation of control systems and construction of a lab test rig. I have had the privilege to work with prominent experts and inspiring individuals. People who are so talented in their field that they can shoot from the hip when leading their projects, but still hit the bulls eye.

One of the lessons learned from my time at Alfa Laval, is the importance of creating conditions for creativity. Creativity is essential for technological development and a prerequisite for corporate success. With success, growth will follow. And as a company grows so does the difficulty of changing it’s course.  That is when it is crucial to promote new ways of thinking and the entrepreneurial spirit of single individuals, or in other words: to maximize the settling velocity of small particles in a viscous fluid. Therefore, Stokes' Law is just as relevant for the development of next generation marine separators as it is for the organizational culture of a large corporation!

Karl Blomberg

Variables of Stokes’ Law
v_s is the settling velocity of small, spherical objects in a viscous fluid
r is the particle radius
g is the gravitational constant (or centrifugal acceleration)
p_p – p_f is the difference in density of the particle and fluid
n is the viscosity of the fluid