Large-eddy simulation (LES) has proven to be a computationally tractable approach to simulate unsteady turbulent flows. However, prohibitive resolution requirements induced by near-wall eddies in ...high-Reynolds number boundary layers necessitate the use of wall models or approximate wall boundary conditions. We review recent investigations in wall-modeled LES, including the development of novel approximate boundary conditions and the application of wall models to complex flows (e.g., boundary-layer separation, shock/boundary-layer interactions, transition). We also assess the validity of underlying assumptions in wall-model derivations to elucidate the accuracy of these investigations, and offer suggestions for future studies.
Ion channels are abundantly expressed in both excitable and non-excitable cells, thereby regulating the Ca(2+) influx and downstream signaling pathways of physiological processes. The immune system ...is specialized in the process of cancer cell recognition and elimination, and is regulated by different ion channels. In comparison with the immune cells, ion channels behave differently in cancer cells by making the tumor cells more hyperpolarized and influence cancer cell proliferation and metastasis. Therefore, ion channels comprise an important therapeutic target in anti-cancer treatment. In this review, we discuss the implication of ion channels in regulation of Ca(2+) homeostasis during the crosstalk between immune and cancer cell as well as their role in cancer progression.
Abstract
While there have been numerous applications of large eddy simulations (LES) to complex flows, their application to practical engineering configurations, such as full aircraft models, have ...been limited to date. Recently, however, advances in rapid, high quality mesh generation, low-dissipation numerical schemes and physics-based subgrid-scale and wall models have led to, for the first time, accurate simulations of a realistic aircraft in landing configuration (the Japanese Aerospace Exploration Agency Standard Model) in less than a day of turnaround time with modest resource requirements. In this paper, a systematic study of the predictive capability of LES across a range of angles of attack (including maximum lift and post-stall regimes), the robustness of the predictions to grid resolution and the incorporation of wind tunnel effects is carried out. Integrated engineering quantities of interest, such as lift, drag and pitching moment will be compared with experimental data, while sectional pressure forces will be used to corroborate the accuracy of the integrated quantities. Good agreement with experimental
$C_L$
data is obtained across the lift curve with the coefficient of lift at maximum lift,
$C_{L,max}$
, consistently being predicted to within five lift counts of the experimental value. The grid point requirements to achieve this level of accuracy are reduced compared with recent estimates (even for wall modelled LES), with the solutions showing systematic improvement upon grid refinement, with the exception of the solution at the lowest angles of attack, which will be discussed later in the text. Simulations that include the wind tunnel walls and aircraft body mounting system are able to replicate important features of the flow field noted in the experiment that are absent from free air calculations of the same geometry, namely, the onset of inboard flow separation in the post-stall regime. Turnaround times of the order of a day are made possible in part by algorithmic advances made to leverage graphical processing units. The results presented herein suggest that this combined approach (meshing, numerical algorithms, modelling, efficient computer implementation) is on the threshold of readiness for industrial use in aeronautical design.
In this paper, a low-power fully acoustic non-destructive testing (NDT) of glass fiber-reinforced composite plate has been presented. Input acoustic power in microwatt range was used for local defect ...resonance (LDR)-based delamination activation. Besides experimental results, numerical simulations were carried out via commercial ABAQUS platform. An oblique incident wave interaction with 3D composite plate was created, and the sound radiation pattern over the plate was studied with an air layer over the plate. In experiment, the sound was generated by a piezospeaker, while a MEMS microphone was used for reception over the plate. Moreover, a laser Doppler vibrometer was utilized for the LDR frequency and corresponding mode shape validation. Frequency spectrum, mode shape at LDR frequency, best wave impinging angle, efficiency, and sound directivity patterns were studied, with angles
θ
,
ϕ
= 10°, 30° being found to correspond to the best direction for sonic excitation. Moreover, fully acoustic system was found to be more efficient than partial acoustic system, i.e., that with contact excitation. The proposed method can be used for inspection of large structures taking advantage of the long-distance non-contact excitation.
The interaction between an incident shock wave and a Mach-6 undisturbed hypersonic laminar boundary layer over a cold wall is addressed using direct numerical simulations (DNS) and wall-modelled ...large-eddy simulations (WMLES) at different angles of incidence. At sufficiently high shock-incidence angles, the boundary layer transitions to turbulence via breakdown of near-wall streaks shortly downstream of the shock impingement, without the need of any inflow free-stream disturbances. The transition causes a localized significant increase in the Stanton number and skin-friction coefficient, with high incidence angles augmenting the peak thermomechanical loads in an approximately linear way. Statistical analyses of the boundary layer downstream of the interaction for each case are provided that quantify streamwise spatial variations of the Reynolds analogy factors and indicate a breakdown of the Morkovin's hypothesis near the wall, where velocity and temperature become correlated. A modified strong Reynolds analogy with a fixed turbulent Prandtl number is observed to perform best. Conventional transformations fail at collapsing the mean velocity profiles on the incompressible log law. The WMLES prompts transition and peak heating, delays separation and advances reattachment, thereby shortening the separation bubble. When the shock leads to transition, WMLES provides predictions of DNS peak thermomechanical loads within $\pm 10\,\%$ at a computational cost lower than DNS by two orders of magnitude. Downstream of the interaction, in the turbulent boundary layer, the WMLES agrees well with DNS results for the Reynolds analogy factor, the mean profiles of velocity and temperature, including the temperature peak, and the temperature/velocity correlation.
High Temperature Gas Dynamics is a primer for scientists, engineers, and students who would like to have a basic understanding of the physics and the behavior of high-temperature gases. It is a ...valuable tool for astrophysicists as well. The first chapters treat the basic principles of quantum and statistical mechanics and how to derive thermophysical properties from them. Special topics are included that are rarely found in other textbooks, such as the thermophysical and transport properties of multi-temperature gases and a novel method to compute radiative transfer. Furthermore, collision processes between different particles are discussed. Separate chapters deal with the production of high-temperature gases and with electrical emission in plasmas, as well as related diagnostic techniques. This new edition adds over 100 pages and includes the following updates: several sections on radiative properties of high temperature gases and various radiation models, a section on shocks in magneto-gas-dynamics, a section on stability of 2D ionized gas flow, and additional practical examples, such as MGD generators, Hall and ion thrusters, and Faraday generators.
An integrated renewable energy (RE) system for powering remote communication stations and based on hydrogen is described. The system is based on the production of hydrogen by electrolysis whereby the ...electricity is generated by a 10
kW wind turbine (WT) and 1
kW photovoltaic (PV) array. When available, the excess power from the RE sources is used to produce and store hydrogen. When not enough energy is produced from the RE sources, the electricity is then regenerated from the stored hydrogen via a 5
kW proton exchange membrane fuel cell system. Overview results on the performances of the WT, PV, and fuel cells system are presented.
Metal hydride thermal compression is a reliable process to compress hydrogen without contamination. We report on the development of a three-stage metal hydride hydrogen compressor. It will compress a ...part of the hydrogen produced by an electrolyser and will recycle the heat released by the electrolytic cells as its principal energy supply. This compressor will raise the hydrogen pressure from 1 to 20
atm, using three hydride compression stages working between 20 and 80
°C. This paper describes the design of the prototype and its connections with the electrolyser. We present our data on the
AB
5
hydride materials that have been characterized and selected. Also, the construction of a lightweight hydride bed reservoir, developed specially for this application, preliminary results on heat transfer, reaction rate and efficiency, are discussed.
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