LIF study of mixing in a model of a vein punctured by a cannula
2002 (English)In: International Journal of Heat and Fluid Flow, ISSN 0142-727X, E-ISSN 1879-2278, Vol. 23, no 5, 664-670 p.Article in journal (Refereed) Published
Steady flow and mixing in a model of an arterialized vein punctured by a cannula as occurs during hemodialysis has been investigated in vitro. The motivation is that a major cause of vascular access dysfunction is the development of venous stenoses. This phenomenon lacks physiological explanation. However, one may attribute this quick process to the chemical content of the dialyzed blood and its flow near the point of infusion. The interest in mixing of chemical compounds in the dialyzed blood supplied through the cannula is, therefore, genuine due to the clinical impacts of haemodyalysis. We are interested in understanding the mixing of the two streams; namely, the untreated blood through the vein and the treated blood through the cannula. This mixing affects the local pH, which in turn can affect the solubility of several salts used for dialysis. In addition, since the blood contains molecules of widely different diffusivity properties, the local composition of blood near the point of injection is of interest. The hypothesis is that concentration non-uniformities may lead to undesired chemical or bio-chemical reactions leading to the pathological processes in the region around the needle. The mixing of a high Schmidt number substance in the stream entering from the cannula with the base flow in the vein is studied by laser induced fluorescence (LIF). The investigations are performed for a range of typical Reynolds numbers in the cannula and the vein found during hemodialysis. The study shows complicated mixing patterns around the cannula, and that non-uniformities in the blood persist over long distances for the lower flow rates found in vivo. For the higher flow rates, the flow loses its stability and mixing is enhanced. The nature of this instability is shown, and quantitative data of concentration fluctuations are given. We have further considered the effect of rotating the cannula. This leads to a significant change in the mixing process. The significance of the non-uniformities in mixing of solvents in the blood for the development of venous stenoses should be further studied not only in fluid dynamical terms but also in terms of endothelial (cellular) effects.
Place, publisher, year, edition, pages
2002. Vol. 23, no 5, 664-670 p.
IdentifiersURN: urn:nbn:se:kth:diva-21656ISI: 000176511800014OAI: oai:DiVA.org:kth-21656DiVA: diva2:340354
QC 201005252010-08-102010-08-10Bibliographically approved