scholarly journals Measured velocity spectra and neutron densities of the PF2 ultracold-neutron beam ports at the Institut Laue–Langevin

Author(s):  
Stefan Döge ◽  
Jürgen Hingerl ◽  
Christoph Morkel
2017 ◽  
Vol 40 (3) ◽  
pp. 109-117 ◽  
Author(s):  
Chan Y. Schüle ◽  
Klaus Affeld ◽  
Max Kossatz ◽  
Christian O. Paschereit ◽  
Ulrich Kertzscher

Background The implantation of rotary blood pumps as ventricular assist devices (VADs) has become a viable therapy for quite a number of patients with end-stage heart failure. However, these rotary blood pumps cause adverse events that are related to blood trauma. It is currently believed that turbulence in the pump flow plays a significant role. But turbulence has not been measured to date because there is no optical access to the flow space in rotary blood pumps because of their opaque casings. Methods This difficulty is overcome with a scaled-up model of the HeartMate II (HM II) rotary blood pump with a transparent acrylic housing. A 2-component laser Doppler velocimetry (LDV) system was used for the measurement of time resolved velocity profiles and velocity spectra upstream and downstream of the rotor blades. Observing similarity laws, the speed and pump head were adjusted to correspond closely to the design point of the original pump – 10,600 rpm speed and 80 mmHg pressure head. A model fluid consisting of a water-glycerol mixture was used. Results The measured velocity spectra were scalable by the Kolmogorov length and the Kolmogorov length was estimated to be between 14 and 24 μm at original scale, thus being about 1.5 to 3 times the size of a red blood cell. Conclusions It can be concluded that turbulence is indeed present in the investigated blood pump and that it can be described by Kolmogorov's theory of turbulence. The size of the smallest vortices compares well to the turbulence length scales as found in prosthetic heart valves, for example.


2010 ◽  
Vol 82 (1) ◽  
Author(s):  
C. M. Lavelle ◽  
C.-Y. Liu ◽  
W. Fox ◽  
G. Manus ◽  
P. M. McChesney ◽  
...  

Author(s):  
О. О. Грицай ◽  
А. К. Гримало ◽  
В. В. Колотий ◽  
В. М. Венедиктов ◽  
С. П. Волковецький ◽  
...  

2016 ◽  
pp. 3524-3528
Author(s):  
Casey Ray McMahon

In this paper, I discuss the theory behind the use of a dense, concentrated neutron particle-based beam. I look at the particle based physics behind such a beam, when it is focused against solid material matter. Although this idea is still only theoretical, it appears that such a beam may be capable of disrupting the stability of the atoms within solid matter- in some cases by passing great volumes of neutrons between the electron and nucleus thus effectively “shielding” the electron from the charge of the nucleus. In other cases, by disrupting the nucleus by firing neutrons into it, disrupting the nucleus and weakening its bond on electrons. In either case- the resulting effect would be a disruption of the atom, which in the case of material matter would cause said material matter to fail, which would appear to the observer as liquification with some plasma generation. Thus, a dense neutron particle based beam could be used to effectively liquefy material matter. Such a beam could bore through rock, metal, or even thick, military grade armour, like that used on tanks- causing such materials to rapidly liquefy. The denser and thicker the neutron beam, the more devastating the effect of the beam- thus the faster material matter will liquefy and the greater the area of liquification. Such a beam would have applications in Defence, mining and drilling operations.


1967 ◽  
Vol 99 (4) ◽  
pp. 954-961 ◽  
Author(s):  
J. ROBERT ANDREWS ◽  
HERBERT HOLLISTER

2021 ◽  
pp. 1-16
Author(s):  
Paul Zakalek ◽  
Jingjing Li ◽  
Sarah Böhm ◽  
Ulrich Rücker ◽  
Jörg Voigt ◽  
...  

Compact accelerator-driven neutron sources allow to operate multiple optimised target-moderator-reflector (TMR) units adapted to the requirements of the respective instruments. The compact design of the TMR units allows an efficient coupling of neutron production, neutron moderation and extraction, but requires a novel way of optimisation. The neutronic performance of different TMR units based on polyethylene, heavy water and a mixture of heavy and light water moderators together with Pb and Be reflectors and a borated polyethylene absorber is discussed. Extraction channels for thermal and cold neutrons are investigated regarding the energy and time spectra.


2021 ◽  
Vol 62 (2) ◽  
Author(s):  
Florian M. Heckmeier ◽  
Stefan Hayböck ◽  
Christian Breitsamter

Abstract The spatial and temporal resolution of a fast-response aerodynamic pressure probe (FRAP) is investigated in a benchmark flow of grid-generated turbulence. A grid with a mesh size of $$M=6.4$$ M = 6.4 mm is tested for two different free-stream velocities, hence, resulting in Reynolds numbers of $$Re_M= \{4300,12800\}$$ R e M = { 4300 , 12800 } . A thorough analysis of the applicability of the underlying assumptions with regard to turbulence isotropy and homogeneity is carried out. Taylor’s frozen turbulence hypothesis is assumed for the calculation of deducible flow quantities, like the turbulent kinetic energy or the dissipation rate. Furthermore, besides the examination of statistical quantities, velocity spectra of measurements downstream of the grid are quantified. Results of a small fast-response five-hole pressure probe equipped with piezo-resistive differential pressure sensors are compared to single-wire hot-wire constant temperature anemometry data for two different wire lengths. Estimates of temporal and spatial turbulent scales (e.g., Taylor micro scale and Kolmogorov length scale) show good agreement to data in the literature but are affected by filtering effects. Especially in the energy spectra, very high bandwidth content cannot be resolved by the FRAP, which is mainly due to bandwidth limits in the temporal calibration of the FRAP and the minimal resolution of the integrated sensors. Graphic abstract


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