|
|
Sound Control of the Turbulent Axisymmetric Air Jet Suitable for Application.
Cvetinović, D. ; Jovanovic, R. ; Vejražka, Jiří ; Tihon, Jaroslav ; Nakabe, K. ; Tatsumi, K.
The subject of this paper is the submerged, round, unconfined turbulent axisymmetric jet, which issues from nozzles with different geometries and impinges to the flat heated plate positioned normally to the jet axis. The aim of experimental investigations, mathematical modeling and numerical simulations is to widely investigate properties and the vortex structures of modified and unmodified jet,that are assumed to have great importance in the heat transfer process. It is found that the vortex roll-up can be controlled by adding small amplitude modulation of the nozzle exit velocity using external source of low-amplitude oscillations or self-sustained oscillations generated in the operation of the specially designed whistler nozzles.
Fulltext: content.csg -  PDF
Plný tet: SKMBT_C22018100509401 - PDF
|
|
| |
|
| |
|
|
Hydrodynamic Behavior of Bubbles in Slot Channels.
Ezeji, Kingsley ; Tihon, Jaroslav
We present the results of laboratory experiments investigating the dynamics of air bubbles rising in stagnant or co-flowing liquid (water) in inclined channels of rectangular crosssections. The experiments were conducted in a basic Plexiglas channel (1300 x 240 x 20 mm, in length (L), width (W), and height (H), respectively). Different channel geometries were obtained by insertion of suitably varied plates into the basic channel. Channel inclinations were ranging from alfa = 5̊ (almost horizontal) to 90̊ (vertical). Measurements and data analysis were carried out with the use of a high speed video camera system and image processing technique providing information on the bubble shape (bubble length LB and volume VB) and bubble rise velocity UB. The specific impact of channel geometry and inclination on the shape, stability, and velocity of rising bubbles was studied and discussed.\n
|
|
| |
|
|
Detection of Apparent Wall Slip in Microdispersion Liquids
Pěnkavová, Věra ; Tihon, Jaroslav ; Wein, Ondřej
Zdánlivý přístěnný skluz je možno detekovat přímo různými vizualizačními technikami, pokud je mikrodisperzní kapalina dostatečně transparentní, nebo nepřímo pomocí viskozimetrie, kdy je měření prováděno v minimálně dvou různých geometriích senzoru. Z rozdílných tokových křivek naměřených v různých geometriích je možno pomocí statistického zpracování vyhodnotit jak viskozitu v objemu disperze, tak skluzový příspěvek podél stěny.
Fulltext: content.csg - PDF
Plný tet: Penkavova at al_CHISA 2015 - PDF
|
|
|
Application of the Electrodiffusion Method forNnear-Wall Flow Diagnostics
Tihon, Jaroslav
The electrodiffusion method is presented as a measuring technique suitable for the flow measurement done in close proximity of the wall, thus in the region difficultly accessible by standard anemometric techniques (e.g. PIV, LDA). The experimental results obtained in different flow configurations (backward-facing step flow, wavy film flow, turbulent channel flow, rising Taylor bubbles) document application capabilities of this technique, e.g. for mapping of wall shear stresses, delimitation of stable flowrecirculation zones, detection of short-time reversal of the near-wall flow, investigation of the near-wall turbulence, or detection of moving fluid particles. A new technology of sensor fabrication based on photolithography is introduced and possible applications of microsensors in microfluidic devices discussed.
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22014011511300 - PDF
|
|
| |
|
|
Application of the Electrodiffusion Method for Near-Wall Flow Diagnostics
Tihon, Jaroslav
The electrodiffusion method is presented as a measuring technique suitable for the flow measurement done in close proximity of the wall, thus in the region difficultly accessible by standard anemometric techniques (e.g. PIV, LDA). The experimental results obtained in different flow configurations (backward-facing step flow, wavy film flow, turbulent channel flow, rising Taylor bubbles) document application capabilities of this technique, e.g. for mapping of wall shear stresses, delimitation of stable flow-recirculation zones, detection of short-time reversal of the near-wall flow, investigation of the near-wall turbulence, or detection of moving fluid particles. A new technology of sensor fabrication based on photolithography is introduced and possible applications of microsensors in microfluidic devices discussed.
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22013110513500 - PDF
|
|
|
The Deflocculation of Kaolin Suspensions – the Effect of Various Electrolytes
Pěnkavová, Věra ; Guerreiro, M. ; Tihon, Jaroslav
The deflocculation effect of conventional additives to kaolin suspensions is evaluated from the results standard rheological measurements. Several widely used electrolytes (NaOH, Na2CO3, Na2SiO3, SHMP = sodium hexametaphosphate, and CMC = sodium salts of carboxymethylcellulose) have been tested. The optimal concentrations of these deffloculants, in respect to reaching the maximum reduction of initial suspension viscosity, are found. The stability of deflocculated kaolin suspensions against sedimentation is evaluated and different aspects of the observed flow enhancement discussed. Inorganic electrolytes are found to be more effective in viscosity reduction, but on the other hand, low-molecular organic CMC additives produce more stable final suspensions.
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22013102415150 - PDF
|
guest ::
