Experimental study of the development of a helium jet during acoustic action

A helium jet subjected to acoustic action is experimentally studied by the particle image velocimetry method. The mechanisms of flow stability loss are discussed. An asymmetric instability mode is shown to develop in the jet subjected to the action of sound, which leads to jet division. Jet vibrations are found to be accompanied by a secondary instability, which manifests itself in the formation of vortices inside the jet.     

The evolution of instabilities in gas microjets under acoustic action

The results of an experimental investigation of the effect of external acoustic perturbations on the stability of millimeter- and submillimeter-scale gas jets flowing out into the atmosphere are presented. Data on flow visualization by the shadow method and the instantaneous velocity fields of the flow by the PIV method are obtained. The sound effect in the jet is shown to lead to the asymmetric mode of instability. The growth of this mode downstream leads to flow bifurcation. Frequency characteristics of the effect for jets of different geometries and jets of different gases are compared.     

Novel Epoxides of Soloxolone Methyl: An Effect of the Formation of Oxirane Ring and Stereoisomerism on Cytotoxic Profile,Anti-Metastatic and Anti-Inflammatory Activities In Vitro and In Vivo

It is known that epoxide-bearing compounds display pronounced pharmacological activities, and the epoxidation of natural metabolites can be a promising strategy to improve their bioactivity. Here, we report the design, synthesis and evaluation of biological properties of αO-SM and βO-SM, novel epoxides of soloxolone methyl (SM), a cyanoenone-bearing derivative of 18βH-glycyrrhetinic acid. We demonstrated that the replacement of a double-bound within the cyanoenone pharmacophore group of SM with α- and β-epoxide moieties did not abrogate the high antitumor and anti-inflammatory potentials of the triterpenoid. It was found that novel SM epoxides induced the death of tumor cells at low micromolar concentrations (IC₅₀^(24h) = 0.7–4.1 µM) via the induction of mitochondrial-mediated apoptosis, reinforced intracellular accumulation of doxorubicin in B16 melanoma cells, probably by direct interaction with key drug efflux pumps (P-glycoprotein, MRP1, MXR1), and the suppressed pro-metastatic phenotype of B16 cells, effectively inhibiting their metastasis in a murine model. Moreover, αO-SM and βO-SM hampered macrophage functionality in vitro (motility, NO production) and significantly suppressed carrageenan-induced peritonitis in vivo. Furthermore, the effect of the stereoisomerism of SM epoxides on the mentioned bioactivities and toxic profiles of these compounds in vivo were evaluated. Considering the comparable antitumor and anti-inflammatory effects of SM epoxides with SM and reference drugs (dacarbazine, dexamethasone), αO-SM and βO-SM can be considered novel promising antitumor and anti-inflammatory drug candidates.     

Streamlining of a cylinder with an electric arc rotating in a magnetic field

Streamlining of a circular cylinder with a localized heat source modeling an MHD actuator in which the plasma arc channel moves along the cylinder surface under the action of the Lorentz force in a radial magnetic field is studied experimentally and simulated numerically. It is shown that the presence of a moving heat release region leads to a break in the symmetry in cylinder streamlining by the external flow and the appearance of a nonzero lift force and circulation.     

Stability of Steel X03Cr23Ni6Mo4Cu3NbN (after ESR) Against the Impact of Products of the Atmospheric Pressure Surface Discharge Plasma

Protection of Metals and Physical Chemistry of Surfaces - Under the effect of the surface discharge in air at atmospheric pressure, the edge of the electrode exposed in the plasma undergoes...     

High-frequency actuator control of air flow near a circular cylinder: Impact of the discharge parameters on the cylinder aerodynamic drag

The impact of capacitive high-frequency surface discharge on a flow around a circular cylinder is studied at airflow velocity of 20–100 m/s and the Reynolds numbers Re < 2.4 × 10⁵. The power of the discharge was modulated at a frequency of 10²–10⁴ Hz, corresponding to the Strouhal number St = 0.1–10. It is shown that the distribution of pressure in the wake behind the cylinder is significantly influenced by the discharge. A decrease in the average diameter of the wake is observed. The parameters of the discharge were measured: the gas temperature, heating rate in the discharge region, and velocity of discharge propagation.     

Structure of RF capacitive discharge in swirl airflow at atmospheric pressure

Conditions for the onset of transitions between corona and pinch types of one-electrode radiofrequency capacitive discharges in swirl airflow at atmospheric pressure have been analyzed. It is established that the transitions observed at various values of the gas flow rate and swirl parameter are related primarily to the gasdynamic structure of airflow. Calculated data obtained in the framework of a proposed theoretical model are qualitatively consistent with the available experimental data.     

Aerodynamic quality management for the NACA 23012 airfoil model using the surface high-frequency discharge

The effect of the surface capacity HF discharge on airfoil flow-around has been studied in the situation when the oncoming flow velocity is 20 m/s and the Reynolds numbers are Re = 10⁵. The power delivered to discharge was modulated with a frequency of 3 × 10²–2 × 10⁴ Hz, which corresponds to a Strouhal number of St = 1.2–80, and the average electric power (W _av) was 50–400 W. It has been indicated that the aerodynamic drag decreased and the lift increased at stall and post-stall angles of attack when the HF dielectric barrier discharge was turned on. A nonstationary stochastic change in the C _x and C _y aerodynamic characteristics was observed at a stall angle in the St = 4–10 range of Strouhal numbers when the power was insufficient (W _av ≈ 100 W).     

Edge effects in flow around a plasma actuator

We have studied the structure of flow formed in the boundary layer at the lateral edge of the discharge zone of a dielectric barrier discharge plasma actuator. It is established that a region with nonzero component of tangential velocity exists near the plasma layer boundary. At some distance downstream of the actuator, a concentrated vortex is formed with the axis aligned with the flow direction. In the presence of two closely spaced boundaries of the plasma region, a pair of counter-rotating vortices is formed. Separate microdischarges in the plasma layer also appear to be a source of similar longitudinal vortices with smaller amplitude.