Влияние динамического напора и молекулярного веса газа на смешение при инжекции струй в поперечный сверхзвуковой поток

The results of a computational study of turbulent supersonic flows in a channel with a backward-facing step are presented, taking into account crossflow injection of argon and hydrogen jets. The calculations are performed at Mach number M = 4 at the channel entrance under the real flight conditions, which were realized in experiments in a hot-shot aerodynamic facility. The comparison of the flowfields is carried out for jet-to-freestream momentum ratio range J = 1 ÷ 6. It is shown that the degree of mixing, estimated from the uniformity index, increases with J increasing and with an increase in the molecular weight of the injected gas at the same J.

Parameters of liquid cooling thermal management system effect on the Li-ion battery temperature distribution

In order to investigated the influence on the liquid cooling system cooling effect by changing the structural parameters, single Li-ion battery heat generation model is conducted, and used in following simulation. Subsequently, sixteen models are designed by orthogonal array, and the results are obtained by extremum difference analysis, which can quantify the influence degree, identify major and minor factors, and find the relatively optimum combination. Finally, different channel entrance layout is adopted to investigated. With a series of work, the effective of single battery heat generation model is proved by the discharge experiment. The coolant velocity has most evident influence on the Li-ion battery temperature rise, rectangular channel aspect ratio is second one, and the heat conducting plate thickness has the smallest influence. Similarly, for Li-ion battery temperature difference, the effect of heat conducting plate thickness and rectangular channel aspect ratio as the same, both are secondary factor, and coolant velocity is main factor. With different channel entrance layout, both the maximum temperatures denote a same upward trend, and better balance temperature distribution is obtained by adopt Case C system which with alternating arrange channel entrance layout.

EXTENDING TRANSIT WINDOWS AND VESSEL DRAFTS IN PORT BOTANY USING A NEXT GENERATION, PHYSICS-BASED OPERATIONAL SYSTEM

Servicing the largest population centre in Australia, Port Botany is vital to the economic wellbeing of Sydney and New South Wales. The channel entrance is often subject to energetic Pacific Ocean swell, moderate tides and occasionally severe winds. In August 2019, the Port Authority of NSW (PANSW) adopted the NCOS ONLINE system to provide enhanced decision support for under keel clearance management of deep drafted vessels in Port Botany. The technical framework and real-life application of the physics-based operational system NCOS ONLINE is presented in this paper.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/uPvX_0DNjRo

Structural basis for substrate gripping and translocation by the ClpB AAA+ disaggregase

ABSTRACTBacterial ClpB and yeast Hsp104 are homologous Hsp100 protein disaggregases that serve critical functions in proteostasis by solubilizing protein aggregates. Two AAA+ nucleotide binding domains (NBDs) power polypeptide translocation through a central channel comprised of a hexameric spiral of protomers that contact substrate via conserved pore-loop interactions. To elucidate the translocation mechanism, we determined the cryo-EM structure of a hyperactive ClpB variant to 2.9 Å resolution bound to the model substrate, casein in the presence of slowly hydrolysable ATPγS. Distinct substrate-gripping mechanisms are identified for NBD1 and NBD2 pore loops. A trimer of N-terminal domains define a channel entrance that binds the polypeptide substrate adjacent the topmost NBD1 contact. NBD conformations at the spiral seam reveal how ATP hydrolysis and substrate engagement or disengagement are precisely tuned to drive a stepwise translocation cycle.

Space–time dynamics of optimal wavepackets for streaks in a channel entrance flow

The laminar–turbulent transition of a plane channel entrance flow is revisited using global linear optimization analyses and direct numerical simulations. The investigated case corresponds to uniform upstream velocity conditions and a moderate value of Reynolds number so that the two-dimensional developing flow is linearly stable under the parallel flow assumption. However, the boundary layers in the entry zone are capable of supporting the development of streaks, which may experience secondary instability and evolve to turbulence. In this study, global optimal linear perturbations are computed and studied in the nonlinear regime for different values of streak amplitude and optimization time. These optimal perturbations take the form of wavepackets having either varicose or sinuous symmetry. It is shown that, for short optimization times, varicose wavepackets grow through a combination of Orr and lift-up effects, whereas for longer target times, both sinuous and varicose wavepackets exhibit an instability mechanism driven by the presence of inflection points in the streaky flow. In addition, while the optimal varicose modes obtained for short optimization times are localized near the inlet, where the base flow is strongly three-dimensional, when the target time is increased, the sinuous and varicose optimal modes are displaced farther downstream, in the nearly parallel streaky flow. Finally, the optimal wavepackets are found to lead to turbulence for sufficiently high initial amplitudes. It is noticed that the resulting turbulent flows have the same wall-shear stress, whether the wavepackets have been obtained for short or for long time optimization.

Positively charged residues at the channel mouth boost single-file water flow

Positively charged residues in the vicinity of the channel entrance or exit accelerate single-file water flow.