Fluid Dynamics最新文献

{"title":"Numerical Simulation of Air Plasma Flow in the Sectioned Discharge Channel of the VGU-3 HF Plasmatron","authors":"S. A. Vasil’evskii,&nbsp;A. F. Kolesnikov,&nbsp;E. S. Tepteeva","doi":"10.1134/S0015462826600446","DOIUrl":"10.1134/S0015462826600446","url":null,"abstract":"<p>The subsonic air plasma flow in a sectioned discharge channel of the VGU-3 plasmatron is numerically investigated on the basis of Navier−Stokes equations, together with two-dimensional equations governing a vortex electromagnetic field. The calculations are performed for the pressures of 100 and 50 hPa and the anode power supply of the HF generator ranging from 100 to 300 kW. The plasma flow parameters, namely, the velocity components, the enthalpy, the temperature, the molar composition, and the Mach and Reynolds numbers are determined at the channel exit in these regimes. The radial profiles of the gas parameters at the channel exit, the parameter distributions along the axis of symmetry from the entry section to the channel exit, and the stream function and temperature contours within the channel are presented. It is shown that the use of a sectioned discharge channel in the VGU-3 plasmatron instead of a simple channel results in the fourfold increase of the longitudinal velocity component and a 10–20% reduction of the flow enthalpy at the axis of symmetry in the exit section for the regimes considered, which makes it possible to extend considerably the range of modeling the full-size aerodynamic heating in the experiments performed at VGU-3.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":"61 2","pages":""},"PeriodicalIF":0.6,"publicationDate":"2026-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147849410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Investigation of the Effect of Surface Roughness on the Shape and Region of Stability of Polygonal Hydraulic Jumps","authors":"E. Soukhtanlou,&nbsp;M. Mokhlesi,&nbsp;A. R. Teymourtash,&nbsp;M. R. Mahpeykar","doi":"10.1134/S0015462825600105","DOIUrl":"10.1134/S0015462825600105","url":null,"abstract":"<p>The size and number of corners of a polygonal hydraulic jump depend on various parameters, including the fluid flow rate, the jet diameter, the obstacle height, and the physical properties of fluid. In other words, the size and shape of the polygonal hydraulic jump depend on the Reynolds number, the Weber number, and the Bond numbers. This study investigates the effect of the surface roughness on the shape and region of stability of polygonal hydraulic jumps. Sandpapers of different degrees of roughness are glued on the surface of the target plate to make it rough. The study reveals that, in addition to the Reynolds and Weber dimensionless numbers, the surface roughness of the target plate affects the stability of polygonal hydraulic jump. Based on the conditions of this study, including the thin-film flow, surface roughness leads to flow slip on the surface and, consequently, leads to a higher mean velocity and flow momentum. This study demonstrates that, in general, at given values of the Reynolds and Weber numbers, a rougher surface leads to a greater number of corners in the polygonal hydraulic jump. Furthermore, the rougher the surface, the smaller the extent of the region of stability of polygonal hydraulic jumps. At last, the Taguchi method is used to derive relations for estimating the number of corners of polygonal hydraulic jumps with respect to the jet diameter, the flow rate, the height of downstream obstacle, and the roughness of the target plate for both modes of increasing and decreasing flow rates.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":"61 2","pages":""},"PeriodicalIF":0.6,"publicationDate":"2026-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147849409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Determination of the Turbulent Prandtl Number","authors":"Yu. K. Rudenko,&nbsp;N. A. Vinnichenko,&nbsp;A. V. Pushtaev,&nbsp;Yu. Yu. Plaksina,&nbsp;A. V. Uvarov","doi":"10.1134/S0015462826600434","DOIUrl":"10.1134/S0015462826600434","url":null,"abstract":"<p>The description of heat transfer processes in physical and chemical gas dynamics within the framework of RANS (Reynolds-averaged Navier–Stokes) turbulence models involves determination of the turbulent thermal conductivity coefficient. Historically, the turbulence models make it possible to find the turbulent viscosity distribution, from which the turbulent thermal conductivity is determined using the turbulent Prandtl number (TPN). However, the TPN can depend on the problem parameters and vary within the flow domain. The applicability of the models proposed for calculating spatial variations in the TPN is restricted to specific flows. For example, the Kays–Crawford model describes the growth of the TPN in the boundary layer near a rigid wall. To validate and improve these models, it is necessary to use experimental verification. In the present study, an experiment carried out for the impact jet of heated gas is considered. The average temperature field, measured using the background oriented schlieren (BOS), contains information on the turbulent thermal conductivity coefficient. The experiment also includes velocity measurements at individual points using a hot-wire anemometer. The physics-informed neural network (PINN) combines the experimental data with equations for reconstructing the fields of hydrodynamic quantities, including the turbulent viscosity and the turbulent thermal conductivity. It is shown that the standard condition of constant turbulent Prandtl number can be used at the center of the jet, but the TPN decreases toward the periphery. The obtained TPN distributions are compared with available studies, both experimental and numerical, using the large eddy simulation (LES) method. The proposed method expands the capabilities for studying various flows in which the temperature field or the concentration field (to determine the turbulent Schmidt number) can be measured, including flows of chemically reacting media.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":"61 2","pages":""},"PeriodicalIF":0.6,"publicationDate":"2026-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147849406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gasdynamic and Thermal Processes Accompanying the Unsteady Interaction of a Shock Wave with a Blunt Cylinder in a Channel","authors":"E. A. Karnozova,&nbsp;I. A. Znamenskaya,&nbsp;V. V. Gubanov,&nbsp;A. A. Filatov,&nbsp;T. A. Kuli-Zade,&nbsp;N. N. Sysoev","doi":"10.1134/S0015462826604171","DOIUrl":"10.1134/S0015462826604171","url":null,"abstract":"<p>The thermal processes accompanying the unsteady interaction between a plane shock wave with the Mach numbers 2.0 to 4.5 and a blunt cylinder is experimentally investigated in the test section of the channel of a shock tube. The relationship between the gasdynamic and thermal processes in the stages of shock wave diffraction and the cocurrent flow past the model and the channel walls is established on the basis of high-speed shadowgraphy (150 000 frames per sec) and infrared thermography (1.5 to 2.8 μm). It is shown that the time of recording infrared radiation from the inner quartz channel walls in the complicated unsteady flow is not greater than 500 to 700 μs and that of radiation from the surface of the cylinder model in flow is not greater than 40 ms.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":"61 2","pages":""},"PeriodicalIF":0.6,"publicationDate":"2026-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147849412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Study of Radiation Characteristics of Air behind the Front of a Strong Shock Wave","authors":"P. V. Kozlov,&nbsp;I. E. Zabelinskii,&nbsp;N. G. Bykova,&nbsp;V. Yu. Levashov,&nbsp;G. Ya. Gerasimov","doi":"10.1134/S0015462826600458","DOIUrl":"10.1134/S0015462826600458","url":null,"abstract":"<p>The results of measurements of the radiation characteristics of air behind a strong shock wave in the DDST-M double-diaphragm shock tube at the Institute of Mechanics of Moscow State University are given. The measurements were performed at an initial pressure of 0.25 Torr in the driven section and shock wave velocities of up to 11 km/s. The shock tube radiation recording system made it possible to record absolute values of the time-integrated spectral density of radiation in the wavelength range of 190–1100 nm and observe the time evolution of radiation in a selected narrow spectral interval in a single experiment.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":"61 2","pages":""},"PeriodicalIF":0.6,"publicationDate":"2026-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147849413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamics of Electric and Gas Dynamic Characteristics of a Spark Discharge in Subcentimeter Gap with an External RLC-Circuit","authors":"E. A. Ermakov,&nbsp;I. E. Ivanov","doi":"10.1134/S001546282660416X","DOIUrl":"10.1134/S001546282660416X","url":null,"abstract":"<p>Dynamics of the streamer development, subsequent closure of the streamer on the electrodes, and formation of a spark channel at the initial temperature 300 K and the pressure 150 Torr in an RLC circuit are studied numerically. The algorithm is based on the drift-diffusion model of the electric discharge in a gas and Euler’s system of equations for describing the ideal gas dynamics. The external part of the electric circuit is taken into account by solving the system of ordinary differential equations in the case of the time dependences of the anode potential, the capacitor voltage, and the electric current. The discharge is initiated by a 0.1 nF capacitor initially charged to a voltage of 25 kV, which discharges through a 0.5 μH inductor, a 100 Ω resistor, and a gas-discharge gap. The dynamics of the electron number density (before and after closure of the interelectrode gap by the streamer) is considered and its relationship with the electric field strength and the electric current density is studied. The pressure, density, and temperature fields during the heat input stage of the spark channel are also studied.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":"61 2","pages":""},"PeriodicalIF":0.6,"publicationDate":"2026-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147849414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Interaction of Dissociated Air with the Surface of Thermal Protection SiO2 and SiC Materials under Experimental Conditions in an HF Plasmatron","authors":"A. A. Krupnov,&nbsp;M. Yu. Pogosbekian,&nbsp;V. I. Sakharov","doi":"10.1134/S0015462826600422","DOIUrl":"10.1134/S0015462826600422","url":null,"abstract":"<p>The stage-by-stage heterogeneous kinetics of the interaction between dissociated air and the surfaces of β-cristobalite and silicon carbide is used to numerically model the supersonic multicomponent nonequilibrium-dissociated air flow past a cylindrical model within the framework of Navier–Stokes equations with account for chemical reactions in the flow under the conditions of heat transfer experiments in the VGU-4 induction HF plasmatron of the Institute for Problems in Mechanics of the Russian Academy of Sciences. A comparative analysis of the calculated flows in the plasmatron for the materials under consideration is carried out in the case of two characteristic surface temperatures, 849 and 1500 K, in a wide range of a parameter characterizing the density of adsorption centers. The contribution of diffusion and heat conduction processes in the heat flux to the surface is determined for different parameters of the interaction between the gas and the surface materials. It is shown that the processes of the nitrogen oxide heterogeneous recombination play the key role in the calculations of the chemical composition of the gas on the surface.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":"61 2","pages":""},"PeriodicalIF":0.6,"publicationDate":"2026-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147849411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of Various Formulations of the Drift-Flux Model in Calculating Unsteady Pipe Flows","authors":"B. I. Krasnopolsky,&nbsp;P. A. Karypidis,&nbsp;D. V. Bykov,&nbsp;A. N. Gryzlov,&nbsp;M. Arsalan","doi":"10.1134/S0015462826604195","DOIUrl":"10.1134/S0015462826604195","url":null,"abstract":"<p>The drift-flux models are the fairly popular choice in the development of engineering applications for simulating multiphase flows in pipes. For this mathematical model, several different ways of writing the system of equations are known in the literature; however, there are no convincing comparison of the results that could be used to make a reasoned choice in favor of a particular model for a given application. This paper reviews several formulations of the drift-flux model in the case of one-dimensional cross-section-averaged equations. Three versions of the model are compared on a number of test problems in terms of the accuracy of modeling the results and the volume of required computations. The obtained results demonstrate good agreement between the different models for steady-state flows, but at the same time, they have significant differences in simulating unsteady flows. Moreover, the choice of a more theoretically justified formulation of the drift-flux model does not provide any significant advantage from the standpoint of comparison with experimental data, but significantly increases the computational effort. The obtained results suggest that differences in the formulations of equations contribute less significantly to the error in the simulation results than ambiguities in the empirical correlations used to close the drift-flux model.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":"61 2","pages":""},"PeriodicalIF":0.6,"publicationDate":"2026-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147849407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diagnostics of Subsonic Air Plasma Jets in the VGU-3 High-Frequency Induction Plasmatron","authors":"A. V. Chaplygin,&nbsp;A. F. Kolesnikov","doi":"10.1134/S0015462826604158","DOIUrl":"10.1134/S0015462826604158","url":null,"abstract":"<p>The distributions of the dynamic pressures and heat fluxes are experimentally investigated in subsonic jets of the VGU-3 HF plasmatron flowing out from a conical water-cooled nozzle with the exit section diameter of 80 mm. The dynamic pressures are measured using a Pitot–Prandtl tube. The heat fluxes are measured using a water-cooled calorimetric probe with copper heat-absorbing surface. The temperature distributions over the outer surface of the quartz discharge channel of the plasmatron are measured using a thermal imager with and without mounting a nozzle. All the experiments are performed at the anode powers of 100 and 250 kW for the pressures in the plasmatron test chamber of 5 and 10 kPa.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":"61 2","pages":""},"PeriodicalIF":0.6,"publicationDate":"2026-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147849408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Investigation of Subsonic and Sonic Jet Control with Finned Stem Tabs","authors":"T. Vijayaraj,&nbsp;S. Thanigaiarasu,&nbsp;T. Thillaikumar,&nbsp;M. Kaushik","doi":"10.1134/S001546282560350X","DOIUrl":"10.1134/S001546282560350X","url":null,"abstract":"<p>The influence of various tab geometry on subsonic and sonic jet mixing control is examined. The tabs, strategically installed at the nozzle exit with the obstruction within 5%, alter the jet flow field. The tab geometries employed include stem-alone, top, and bottom finned stem tabs. The stem alone tab resembles a plain rectangular tab. Finned stem tabs indicate fins configured on the stem tab. The study investigates the effect of fins location on the stem alone tab in mixing of axisymmetric subsonic and sonic jets. The total pressure measurements and the shadowgraph visualization techniques were utilized to estimate the efficacy of the stem-alone tab as well as the top and bottom finned stem tab. Measurements of the total pressure were made in the subsonic and sonic jet flow fields. At the highly underexpanded sonic jet condition with a pressure ratio of 4, the shadowgraph visualization is performed. The measurement of potential core length and the investigation of jet decay is done using axial pressure measurements. The potential core length of stem and finned stem tab-controlled jets was lower than that of uncontrolled jets. The top and bottom finned stem tab controlled sonic jet results in the greatest core length reduction of 78%. Additionally, the tab-controlled jet decays at a faster rate than the uncontrolled jet. The bottom finned stem tab-controlled jet had the highest rate of decay among the tab-controlled jets. The spreading characteristics of the uncontrolled and tab-controlled jets are investigated using radial pressure profiles. The bottom finned stem tab controlled jet achieves the greater spread rate. The differences in the shock cell structures parallel and perpendicular to the stem tab directions were visible in the shadowgraph images taken at highly under expanded sonic jet condition. Furthermore, the bottom finned stem tab produced the comparatively weakest waves, which is advantageous from an aeroacoustics perspective, and the tab insertion produced weaker waves in the jet field. The visualization results align with the data from the pressure profile.</p>","PeriodicalId":560,"journal":{"name":"Fluid Dynamics","volume":"61 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2026-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147737727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}