Blood is thicker than water - and it flows differently

Blood is thicker than water - and therefore flows differently:
international scientific team investigates instabilities in blood flows

The way blood flows through the blood vessels plays an important role in the development of cardiovascular diseases such as thrombosis and arteriosclerosis. However, the physical basis of the blood stream is hardly known. Blood is more heterogeneous than water and is driven by a pump, the heart, it pulsates. However, previous experiments on flow behavior have generally been based on water that moves uniformly. An interdisciplinary team of physicists, engineers and medical scientists is now hoping to close this knowledge gap - and the Centre of Applied Space Technology and Microgravity (ZARM) at the University of Bremen is part of it.

Pumps and channels, hearts and vessels

Both in technical and biological systems pulsating flows are omnipresent. The pulsed acceleration of the fluid by pumps - or by the human heart - often leads to phenomena that can lead to technical problems or cardiovascular diseases. The newly established research group "Instabilities, bifurcations and migration in pulsating flows" deals with diseases that affect many people and are often fatal: Sedimentation in the blood vessels, thromboses and similar ailments, in which particles are accumulated in the bloodstream and impede blood flow, so that in the worst case the cardiovascular system collapses. These sediments occur, for example, where the blood can no longer flow normally. Precise knowledge of the flow behavior of blood could therefore help to better understand the causes of these diseases - and in the medium term also to prevent these diseases or to treat them more effectively.
The basics of the fluid dynamics of blood and other similarly complex fluids that are also driven by a pump are largely unexplored. Not only in the human body, but also in industry, fluids do not flow uniformly through a simple tube system. In the vast majority of cases, they pulsate at a certain rate. Put simply, they are sometimes slower (when the pump is not pumping) and sometimes faster (when it is pumping). Also at different places of pipe system, flow-speed varies or interactions between flow and wall occur, resulting in turbulences. If something other than water flows through the pipes, such as blood or paint, and if the pipe system is as complex as the blood vessel system, simulations of these flows are highly sophisticated.

Simulation of blood circulation

The research group now wants to meet this challenge. In the coming years, it will investigate the laws according to which complex liquids flow through such pipeline systems. First, the influence of a pulsating drive on the simplest system, i.e. water, will be investigated. Based on this, the complexity of the fluid is increased, right up to the composition of blood. In addition to straight tubes, various flow geometries will be used, such as curves or elastic walls. The methods used range from experiments with turbulent flows to computer simulations and measurements in blood vessels. The aim is to gain a basic understanding of blood flows and thus to be able to break down highly complex interacting processes into their constituent parts. On this basis, the urgently needed theoretical description of instabilities in blood flows can be achieved.

Project perspective and participants

At the end of the first funding period of three years, the scientists will have developed the basis for a viable theoretical model of the flow behavior of blood and similar fluids and verified it with experiments. If the German Research Foundation (DFG) decides to continue funding the research group, the scientists could expand their findings into a complete physical model of blood flow.
The research group FOR 2688 "Instabilities, bifurcations and migration in pulsating flows" will be funded by the DFG for three years from August 2019 with approximately 2.4 million euros. The University of Bremen will receive 700,000 euros of this sum. Other partners in the network are Saarland University, Bayreuth University and the Helmholtz Institute N├╝rnburg-Erlangen, the IST in Klosterneuburg near Vienna and the Swiss Federal Research Institute WSL in Zurich.


contact for scientific questions:

Dr. Kerstin Avila
Tel.: 0421 218-57859
E-Mail: kerstin.avila(at)zarm.uni-bremen.de


contact for media inquiries:

Birgit Kinkeldey
Tel.: 0421 218-57755
E-Mail: birgit.kinkeldey(at)zarm.uni-bremen.de