|
|
Matematické modelování proudění krve
Michalová, Marie ; Hron, Jaroslav (advisor) ; Průša, Vít (referee)
At first we point out some important properties and behaviour of blood and blood particles. In the next part we approximate steady two-dimensional Pois- seiulle flow between two parallel plates. We show analytical solutions for New- tonian and power-law models. According to observations of Fahraeus-Lindquist effect we show two-layer models combining previously mentioned models. In the last section we model pulsatile Poisseuille flow and we show analytical and nu- merical results for some pressure and viscosity values. In the end we show our best model, where we shift pressure gradient and get closer to the real blood flow characteristics. 1
|
|
|
Flow instabilities due to torsional oscillators in superfluid helium
Skokánková, Tamara ; Schmoranzer, David (advisor) ; Urban, Pavel (referee)
This Thesis is devoted to the investigation of superfluid helium flows due to torsional oscillators. In its first part, flow due to a torsionally oscillating disc suspended on a tungsten filament is studied (building upon the work of A. C. Hollis Hallett from 1952). Measurements of the motion of the torsionally oscillating disc were performed in superfluid helium at temperatures between 1.265 K and 2.157 K at saturated vapour pressure. Time traces of the disc angular deflection were obtained, and critical parameters related to the turbulent flow stability were determined. In laminar flow, scaling of drag forces with the dimensionless Donnelly number was verified. Based on these results, and comparison with the original work, a scenario of the decay of turbulent flow was suggested. The second part of this work is focused on the development and construction of a similar experiment for mK temperatures. A new type of oscillator was designed, a so-called "pillbox", and a series of testing measurements was performed both at room and mK temperatures.
|
|
|
Low frequency oscillatory flow of cryogenic helium
Skokánková, Tamara ; Schmoranzer, David (advisor) ; Babuin, Simone (referee)
This work is based on the experiment that was carried out by R. J. Donnelly and A. C. Hollis Hallett in 1958. Measurements were carried out with a torsionally oscillating disc in superfluid helium over a temperature range of 1.37 to 2.16 K at saturated vapor pressure. We were able to measure time dependences of the angular velocity of the disc and to determine critical values of the angular velocity amplitude. The obtained temperature dependences also show that the measured nonlinear forces originate from the superfluid component. Based on these measurements, a model describing the mechanisms of the transition to turbulence in a flow due to a torsionally oscillating disc is proposed. Powered by TCPDF (www.tcpdf.org)
|
|
|
Matematické modelování proudění krve
Michalová, Marie ; Hron, Jaroslav (advisor) ; Průša, Vít (referee)
At first we point out some important properties and behaviour of blood and blood particles. In the next part we approximate steady two-dimensional Pois- seiulle flow between two parallel plates. We show analytical solutions for New- tonian and power-law models. According to observations of Fahraeus-Lindquist effect we show two-layer models combining previously mentioned models. In the last section we model pulsatile Poisseuille flow and we show analytical and nu- merical results for some pressure and viscosity values. In the end we show our best model, where we shift pressure gradient and get closer to the real blood flow characteristics. 1
|
guest ::
