Flow in Glass Models Simulating Vascular Junctions Under Steady Flow Conditions

Abstract

SUMMARYThe dye-injection technique was used to study flow patterns in twelve glass models of the union of two streams to form a common stem as occurs in veins and, less often, in arteries. The angle of union and the sharpness of the apex of the union varied. Flow disturbances, though minor at low flow rates, were observed in the stem beyond the junction in all models at Reynolds numbers below 2000. The disturbances were attributed to instability in the wake of the junction and to boundary layer separation at the apex. The results indicate possible applicability to the human vascular system.

Flow patterns from metallic vascular endoprostheses: in vitro results

“…The principles of our flow model (glass tubes, steady flow conditions) for in vitro testing of stents is based on systems which have already been established for cardiology and cardiovascular surgery. They are used to determine flow patterns and pressure gradients of mechanical heart valves [9] or for simulating vascular junctions [8]. Radiologists used a similar model for the evaluation of fluid dynamics of endoluminal stented grafts in aneurysms to prove stasis in the surrounding dead space after stent-graft implantation [16].…”

“…Since cells, e. g. red blood cells, have elastic properties, flow dynamics of a pure fluid blood do not correspond totally to those of blood. According to the number of Euler (Eu; C) pressure gradient in a human organism would therefore be 6 % higher as compared with our model [8,9]. Differences in viscosity between saline (d = 1 10 ±3 Pa s) and blood (d = 3.6 10 ±3 Pa s) have no influence on the pressure gradient [10].…”

“…Instead of technically feasible ªplug flowº velocity determination (severe source of error), which differs in vessels due to velocities radial distribution in vessels [13], the flow was regulated with a computercontrolled centrifugal gear mechanism supported pump (FC-71 MP; Ismatec, Wertheim-Mondfeld, Germany) and controlled with flow measurement (type 800; Gemü, Ingelfingen, Germany). The temperature of the whole model, filled with saline (4 l), was 27 Celsius [8,9,10].…”

“…The inner diameter of the tube (Dr) measured 9 mm. To achieve laminary flow, the straight in-flow tract (L) measured 81 cm based on the Reynolds law [8].…”

Synthesis and antioxidant evaluation of novel silybin analogues

“…General procedure for the preparation of (^ (7). A mixture of 1.48 mmol of 5, 1.48 mmol of alcohol 6, 60 ml of benzene and 20 ml of acetone was placed in oil bath at 608C and the solution was stirred for 10 min.…”