The transonic turbulent two-dimensional airflow over a symmetric flat-sided double wedge is studied numerically. Solutions of the Reynolds-averaged Navier-Stokes equations are obtained with ...ANSYS-18.2 CFX finite-volume solver of second order accuracy on a fine mesh. The solutions demonstrate an extreme sensitivity of the flow field and lift coefficient to variation of the angle of attack α or free-stream Mach number M∞. Non-unique flow regimes and hysteresis in certain bands of α and M∞ are identified. Interaction of shock waves and local supersonic regions is discussed. The study confirms a concept of shock wave instability due to a coalescence/rupture of supersonic regions. In addition to the instability of shock wave locations, the numerical simulation shows a buffet onset, i.e., self-exciting oscillations due to instability of a boundary layer separation at the rear of wedge. Curious flow regimes with positive lift at negative angles α and, vice versa, with negative lift at positive angles α, are pointed out. A piecewise continuous dependence of the lift coefficient on two free-stream parameters, α and M∞, is discussed.
The two-dimensional turbulent airflow in a 9-degrees-bent channel is studied numerically. Inner surfaces of the top and bottom walls are parallel to each other upstream and downstream of the bend. ...The free stream is supersonic, whereas the flow is subsonic at the channel exit. Solutions of the Reynolds-averaged Navier-Stokes equations are obtained with a finite-volume solver using the Spalart-Allmaras and Shear Stress Transport k −! turbulence models. The solutions reveal a flow hysteresis and non-uniqueness in considerable bands of the free-stream Mach number, angle of attack, and exit pressure. At the endpoints of the bands, there are abrupt changes of the shock wave system. The non-uniqueness admits different losses of the total pressure, which may cause different trusts of an air breathing engine.
Coal-water fuel is a promising substitution of conventional fossil fuels for the countries, where clean energy sources like wind, solar, etc. cannot cover energy demand. However, this fuel has a lot ...of specifics for preparation, transportation, and combustion. Issues with coal-water fuel combustion can be solved with the use of fuel activation. The catalytic activation of the coal-water fuel produced from coal of different metamorphic stages with the help of titanium dioxide nanoparticles was experimentally studied. The research suggests that the addition of the titanium dioxide nanoparticles in 0.5–4% wt. increases the coal-water fuel thermal conductivity by 9–17% while the value of heat capacity decreases by 12–23%. Also, this addition decreases time delay before fuel ignition by 20–22% and a total time of the fuel droplet burning by 15%; increases maximum temperature of the volatiles combustion by 8–10%; and increases combustion completeness as well. For the first time, the optimal value of the nanoparticles additive content has been found.
Few methods have been introduced and used in simulation fluid flows using lattice Boltzmann method (LBM) with external forces, such as buoyancy, surface tension, magnetic, etc. In some problems, the ...external force is constant, for instance gravitational force with constant density flows, while for other problems the force may vary spatially and/or temporally with non-zero gradients, such as gravitational force with variable density flows. For problems with the variable force term, adding force term to LBM may not be trivial. The paper evaluates mainly three different schemes of adding force term to LBM with BGK method. In this work, natural convection in a closed and an open ended cavities were used as a test platform. The results for the differentially heated cavity are introduced first. For the open cavity, the vertical left hand wall of the cavity is heated and opposing side is opened to the ambient, with other connecting boundaries are assumed to be adiabatic. Prior to the solution, the boundary conditions at the opening are unknown. The results of predictions using LBM are compared with results predicted by using finite volume method (FVM). The results are presented for
Ra
=
10
6
and for
Pr
=
0.71
. It is found that most methods suggested in the literature produces similar results, despite that some authors claim that their scheme is more accurate than the other schemes.
The dependence of tumors on glycolysis for ATP generation offers a rationale for therapeutic strategies aimed at selective inhibition of the glycolytic pathway. Analysis of tumor cell responses to ...anticancer drugs revealed that inhibition of glycolysis by 2‐deoxy‐D‐glucose (2‐DG) generally augmented the apoptotic response; however, in HCT116 human colon carcinoma cells, apoptosis was suppressed. A comparison of neuroblastoma SK‐N‐BE(2) and HCT116 cells revealed, that in contrast to HCT116, in SK‐N‐BE(2) cells 2‐DG alone was able to induce cell death. In SK‐N‐BE(2) cells the decrease in ATP levels upon treatment with 2‐DG was more prominent because in HCT116 cells mitochondria compensated for the loss of ATP caused by glycolysis suppression. In both cells lines 2‐DG triggered endoplasmic reticulum (ER) stress, assessed by the accumulation of the marker protein GRP78/BiP. Suppression of ER stress by mannose attenuated the 2‐DG‐induced apoptotic response in SK‐N‐BE(2) cells, implying that apoptosis in these cells is a consequence of ER stress induction. In HCT116 cells, ER stress stimulated autophagy, assessed by the accumulation of the lipidated form of LC3. The inhibitor of ER stress mannose attenuated autophagy and reversed 2‐DG‐mediated suppression of cisplatin‐induced apoptosis. When autophagy in HCT116 cells was suppressed by bafilomycin, cisplatin‐induced apoptosis was decreased. At the same time, stimulation of autophagy in SK‐N‐BE(2) cells suppressed cell death. Thus, successful treatment of tumors with conventionally used anticancer drugs should be combined with targeting metabolic pathways involved in the regulation of apoptosis, autophagy, and cellular bioenergetics.
Suppression of glycolysis by 2‐deoxy‐D‐glucose (2‐DG) stimulates apoptosis in SK‐N‐BE(2), but attenuates in HCT116 cells. In both cell lines 2‐DG stimulates stress of endoplasmic reticulum (ER), which ends up in apoptosis in SK‐N‐BE(2) but in autophagy in HCT116 cells. Prevention of ER stress by mannose attenuates apoptosis in SK‐N‐BE(2) cells, and reverses suppression of apoptosis in HCT116 cells.
Turbulent airflow in a supersonic intake model of rectangular cross-section is studied numerically. Instability of shock waves formed in the intake and ahead of the entrance is examined. Solutions of ...the Reynolds-averaged Navier–Stokes equations are obtained with a finite-volume solver of second-order accuracy. The expulsion and the swallowing of the shocks with a variation of free-stream parameters are studied at both subsonic and supersonic conditions prescribed at the outlet. Hysteresis in the dependence of 2D flow on the free-stream velocity and angle-of-attack is documented. An influence of 3D effects on the flow is examined.
A two-stage method is proposed for controlling the regulators in the fuel burnup process during a single operating period. At the first stage, the coefficient of the heat release irregularity at the ...initial time moment is minimized; at the second stage, the instability criterion for a specified time interval is minimized. The linear interpolation of the neutron flux constructed on the basis of perturbation theory is considered to improve the calculation accuracy without high computational costs.
This work addresses two- and three-dimensional turbulent flow in simple channels, modeling the air intakes of rectangular cross section. Flow regimes with a supersonic free stream and supersonic ...velocities at the throat or immediately downstream of the throat are considered. Bifurcations of the shock wave arising ahead of the cowl are studied numerically. Solutions of the Reynolds-averaged Navier–Stokes equations are obtained with a finite-volume solver of second-order accuracy on fine computational meshes. The solutions reveal jumps of the shock leg position with variations of the free-stream Mach number. The dependence of the shock position on the cowl slope and streamwise location of the throat is examined.
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