3,381 research outputs found
Measurements of small radius ratio turbulent Taylor-Couette flow
No full textIn Taylor-Couette flow, the radius ratio () is one of the key parameters of the system. For small , the asymmetry of the inner and outer boundary layer becomes more important, affecting the general flow structure and boundary layer characteristics. Using high-resolution particle image velocimetry we measure flow profiles for a radius ratio of 0.5 and Taylor number of up to . By measuring at varying heights, roll structures are characterized for two different rotation ratios of the inner and outer cylinder. In addition, we investigate how the turbulent bursts coming from the inner and outer cylinder affect the flow profiles. These results exemplify how curvature affects flow in strongly turbulent Taylor-Couette Flow
a_POCT_suppl_data_final – Supplemental material for Point-of-care coagulation testing for reducing in-hospital delay in thrombolysis
No full textSupplemental material, a_POCT_suppl_data_final for Point-of-care coagulation testing for reducing in-hospital delay in thrombolysis by Jung Hee Han, Seongsoo Jang, Mi-Ok Choi, Mi-Jeong Yoon, Seung-Bok Lim, Jeong-Ran Kook, Dong-Wha Kang, Sun U Kwon, Jong S Kim and Sang-Beom Jeon in Hong Kong Journal of Emergency Medicine</p
Dynamics of finite-sized light spheres in turbulence
No full textWe report experimental results on the Lagrangian dynamics of finite-size light particles in turbulence. Using an orthogonal camera setup and 3D particle tracking, we study the velocity and acceleration statistics of rigid light spheres in a water tunnel with nearly homogeneous and isotropic turbulence. The Reynolds number (ReY) is varied from 180 to 300, and the study covers a range of size ratios (4 < D/η < 16) for marginally light spheres. We find that the normalised acceleration PDF decreases in intermittency with increasing size ratio - in qualitative agreement with the predictions of the Faxén corrected model. We also present preliminary results on the rotational dynamics of large light spheres in turbulence
Bulk statistics of stable and decaying Taylor-Couette turbulence
No full textIn this talk we focus on the velocity fluctuations in highly turbulent Taylor-Couette flow for the case of stable flow (constant rotation) and for decaying flow. Turbulent flows are generally characterized by the range of scales of their fluctuations, and a statistical description of the flow is often done by calculating the correlations of velocity fluctuations. These correlations are found to behave like power-laws over a range of scales, and their exponents characterize a certain geometry of flow. Many systems have been investigated carefully: Pipe-flow, Von Kármán flow, Rayleigh Bénard convection, \textit{et cetera}. There are, however, few reports \cite{lew99,she01} quantifying the turbulent properties in Taylor-Couette flow. In the presented work \cite{huisman2013b} we measure the longitudinal structure functions using laser Doppler anemometry, which is a non-intrusive technique and is able to measure the components of the velocity, and thus ideal for obtaining structure functions and the local velocity. We present the statistics of the turbulent velocity fluctuations for counter rotation for varying
Influence of Magnetic Diffusion on Short-Wavelength Magnetic Buoyancy Instability
No full textMagnetic buoyancy instability (MBI) is believed to plays an important role in the evolution of magnetic fields in astrophysical objects. In the Sun large-scale toroidal magnetic field is probably generated in the tachocline – a thin region of strong radial shear, between radiative and convective zones. Observations indicate that this field rises the surface and create active regions. MBI is a probable mechanism for this phenomenon. Magnetic and thermal diffusivity are parameters of solar plasma which could be important for dynamics of MBI. Here we consider preliminary case which include only magnetic dissipation. The singular perturbation methods are used to find difference with case without any dissipation
Thermal comfort in sun spaces: To what extend can energy collectors and seasonal energy storages provide thermal comfort in sun space?
No full textPreparation for fossil fuel substitution in the building sector persists as an essential subject in architectural engineering. Since the building sector still remains as one of the three major global end energy consumer – climate change is closely related to construction and design.
We have developed the archetype sun space to what it is today : a simple but effective predominant naturally ventilated sun trap and as well as living space enlargement. With the invention of industrial glass orangery’s more and more changed from frost protecting envelopes to living spaces from which we meantime expect thermal comfort in high quality.
But what level of thermal comfort provide sun spaces? And to what extend may sun spaces manage autarkic operation profiting from passive solar gains and, beyond that, surplus energy generation for energy neutral conditioning of aligned spaces? We deliver detailed information for this detected gap of knowledge.
We know about limited thermal comfort in sun spaces winter times.
This reasons the inspection of manifold collector technologies, which enable to be embedded in facades and specifically in sun space envelopes. Nonetheless, effective façade integrated collectors are ineffective in seasons with poor irradiation. Hence, the mismatch of offer and demand we have experienced with renewable energies ignites thinking about appropriate seasonal energy storages, which enlarges the research scope of this work. This PhD thesis project investigates on both, a yearly empirical test set up analysis and a virtual simulation of different oriented and located sun spaces abroad Germany. Both empirical and theoretical evaluation result in a holistic research focusing on a preferred occupation time in terms of cumulative frequencies of operational temperature and decided local discomfort, of potential autarkic sun space operation and prospective surplus exergy for alternative heating of aligned buildings. The results are mapped geographically for Germany.
Fossil fuel substitution, as far as this thesis elaborated, is closely related to quality of thermal comfort, sun space orientation and energetic standard of the aligned building. Unexpectedly, spaces, which define envelopes incorporating collectors in combination with storage technologies both profit and suffer to some extend in respect to thermal comfort.
Essentially, we can conclude, that the more area-wise efficient and the more integral the collector technology is incorporated into façade design, the more distinct significance of thermal comfort quality and fossil fuel substitution is.
Eventually, this dissertation determines the potential of a new generation of sun spaces in the context of energy transition
Double diffusive convection between two parallel plates with different boundary conditions
No full textWe investigate the double diffusive convection between two parallel plates with either no-slip or free-slip boundary conditions. Direct numerical simulations have been conducted systematically for a series of control parameters. Salt fingers can be observed for both boundary conditions and all parameters explored. Compared to the no-slip case, salt fingers are stronger in the free-slip case, which is accompanied by larger salinity flux and flow velocity. For both boundary conditions, thin boundary regions develop adjacent to two plates. The salinity flux and the Reynolds number show similar dependences on the control parameter, namely, the Rayleigh number of the salinity field
The Göttingen rotating turbulent Rayleigh-Bénard convection facility
No full textThermally driven turbulent convection under the influence of global rotation is ubiquitous in nature. Well known examples are the outer convective shell of our Sun and the outer liquid core of the Earth. Trying to understand the underlying dynamics of such flows is highly challenging, not only because of the enormous range in length- and time-scales that are involved with these geo/astrophysical cases and the complex interaction of hydrodynamics with electromagnetism, but also because direct measurements on these systems are most often impossible to carry out. We gain access to direct measurements by isolating part of the problem: We focus solely on the hydrodynamical aspects of turbulent convection by performing experiments in the lab and making comparisons with direct numerical simulations (DNS). The canonical system that we use to study such flows is Rayleigh-B\'enard convection (RBC), the flow between a warm bottom plate and cold top plate, in a fluid-filled upright cylindrical cell that is rotating around its geometrical axis. This presentation will focus on the newly constructed rotating RBC facility at the Max Planck Institute for Dynamics and Self-Organization (MPIDS) in G\"ottingen
The first complete sequence and genome structure of daphne virus Y
No full textFrom Daphne odora Thunb., an ornamental shrub in the Republic of Korea, a potyvirus was identified that has an RNA genome of 9,448 nucleotides (excluding the 3′-terminal poly(A) tail) encoding a polyprotein of 3,065 amino acids, with nine putative protease cleavage sites producing ten proteins. Since this potyvirus shared the highest nucleotide sequence identity (91？%; query coverage 5？%) with the available partial sequence of daphne virus Y (DVY) from New Zealand (EU179854), it was considered a Korean isolate of DVY. This is the first molecular characterization of the complete genome sequence of a DVY isolate.open
Till tolkningen av Rölundastenen (U 670)
No full textThe rune-stone U 670 is badly damaged, and was when it first was recorded in the 1600s. Its inscription was read by Elias Wessén as follows: …--n : -…s… eftiʀ : aist : sun : sin : kus na-…. This may be interpreted in Runic Swedish and translated as: … æftiʀ Æist, sun sinn …, “… (this stone) in memory of Æistr, his son …”. Wessén suggests that the final six runes may represent a prayer, beginning Guðs nāð(iʀ) …“The grace of God …”. This short notice shows that no such prayer could be expected on a Viking Age rune-stone. Instead, the author interprets this runic sequence as yet another epithet of the deceased: Kūss ne[fa](?) “the nephew(?) of Kūss”. The name Kūss ‘hunch(back)’ written kus is known from three other rune-stones (U 380, U 640, and U 648), all within 30 kilometers of U 670, and all of which quite possibly refer to the same man. https://doi.org/10.33063/diva-491886</p
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