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This article studies a priori error analysis for linear parabolic interface problems with measure data in time in a bounded convex polygonal domain in R2. Both the spatially discrete and the fully discrete approximations are analyzed. We have used the standard continuous fitted finite element discretization for the space while, the backward Euler approximation is used for the time discretization. Due to the low regularity of the data of the problem, the solution possesses very low regularity in the entire domain. A priori error bounds in the L²(L²(Ω))-norm for both the spatially discrete and the fully discrete finite element approximations are derived under minimal regularity with the help of the L²-projection operator and the duality argument. Numerical experiments are performed to underline the theoretical findings. The interfaces are assumed to be smooth for our purpose.

The article solves the problem of determining the temperature on the inner wall of a hollow cylinder. Using a time Fourier transform, the problem is reduced to an ordinary differential equation, with the help of which the Fourier transform of an exact solution of the inverse boundary value problem is found. A projection regularization method is considered, which makes it possible to obtain a stable solution to the problem and an accurate in order of magnitude estimate of the error of the approximate solution. Since high accuracy requirements are imposed on solutions of such problems in numerical calculations, an algorithm is developed to improve the accuracy and reliability of processing the results of thermal test data. To check the performance of the algorithm, test calculations are carried out.

A numerical and experimental study of the flow near a standard civil-aircraft model at large angles of attack in the range from 0 to 90° and at subsonic velocities of the oncoming flow has been carried out. The experiments were performed in the T-105 wind tunnel of TsAGI. The calculations were carried out within the framework of solving the Reynolds equations. A comparison of the calculated and experimental integral characteristics showed a good agreement with an accuracy sufficient for practice. Physical features of the flow and their influence on the aerodynamic characteristics of a stationary model at large angles of attack, as well as in the mode of rotation of the model with a constant angular velocity, are revealed.

The generation and development of Görtler vortices in a compressible boundary layer on a concave surface has been numerically modeled. The calculation was carried out using the Fluent software of the Ansys program package. Stationary and non-stationary perturbations are analyzed at oncoming-flow Mach number M ≈ 4. It is shown that when a periodic disturbance in the direction transversal to the flow is introduced, it decays on the straight section of the surface, and grows on the concave surface. Comparison of the results of the calculations made with the calculations performed within the framework of the linear theory of stability showed that the range of susceptibility of the boundary layer to disturbances on the concave surface amounts approximately to 17 boundary-layer thicknesses. After the susceptibility zone, disturbances grow exponentially with small deviations. The flow fluctuation profiles are in good agreement with the data obtained from the linear theory of stability. It is shown that the development of a non-stationary perturbation along the surface of the model for the parameters considered in the present study differs little from that of a stationary perturbation.

Data of experimental studies on hydrodynamics of countercurrent flows of liquid and vapor in distillation columns with structured packings are necessary for verification of computational models that describe hydrodynamics and processes of heat and mass transfer in industrial distillation columns. The paper presents a description of the design of a multipoint hot-wire anemometer with a coordinate device, developed to measure the steam flow rate under conditions of jet irrigation of the packing with a countercurrent flow of freon mixture phases. The measurement system was tested with air flowing through a 210-mm layer of Sulzer 500X structured packing. The measurements were carried out using a large-scale research model of a distillation column with a diameter of 900 mm. Experimental data were obtained on the distribution of the local air flow velocity at the outlet of a single-layer Sulzer 500X packing. Scanning the packing plug with a step of 1 and 5 mm showed the presence of a periodic cellular pattern of the gas flow velocity distribution, which correlates with the structure of the studied packing.

The Direct Simulation Monte Carlo (DSMC) method is used to study rarefaction effects on the structure of an axisymmetric underexpanded jet. A comparison with the data of other researchers shows that DSMC simulations accurately reproduce the features of the steady shock-wave structure of the jet. Rarefaction produces a noticeable effect on the jet flow. In particular, it makes the barrel shock in the first shock cell change the type of its reflection from the axis, which leads to vanishing of the developed Mach disk and to changes in the structure of other shock cells. For the first time, the formation of a closed reverse flow region behind the Mach disk is observed in a molecular-kinetic simulation. This phenomenon has been earlier observed only in continuum simulations.

The influence of asymmetric boundary conditions on flow regimes in a model hydraulic turbine has been investigated. The curved draft tube is shown to have almost no effect on the vortex structure, preserving such a phenomenon as the re-connection of the vortex core. The axial and tangential velocity profiles also remain unchanged. There is a change in pressure pulsations, despite the similarity of the average values and the unsteady vortex flow pattern. In the case of an asymmetric model, the pressure pulsation is higher than for a symmetric model. This may indicate a superposition of pulsations, caused by the rotation of a precessing vortex core, with generated longitudinal (synchronous) pressure fluctuations.

The paper presents the research into small multirotor vehicles that fly in the surface layer of the atmosphere, where the level of flow disturbances impinging on the blade can change significantly, altering the characteristics of the propeller. Axial streamlining of a constant-pitch two-blade rotor with a diameter of 380 mm was experimentally studied in a low-noise wind tunnel T-324 of ITAM SB RAS. The experiment was carried out in the range of Reynolds numbers up to 1.5∙10⁵, calculated from the flow parameters in the cross section of 75% of the rotor radius. The thermoanemometric method was used as the main measurement method. The influence of pulsations of the incoming flow on the flow characteristics in the propeller wake was established.

In this paper, the characteristics of the electric field, flow field and temperature field of ionic wind heat sink are studied, respectively. The results show that the heat sink achieves the best performance when the ratio of fin spacing to thickness is 5, the electrode spacing is 5mm, the needle position is 0. Furthermore, a two-stage structure ionic wind heat sink is proposed and optimized. The optimized average wind velocity increased by 30.8% to 3.57m/s compared to the single-stage structure. This work enriches the knowledge of electrode configuration and promote the application of ionic wind heat sinks.

The operation of the centrifugal disk pump is experimentally studied. To summarize experimental data, dimensionless parameters are introduced. A method for calculating the flow rate, pressure, and throttle characteristics is proposed. The method ensures accuracy sufficient fort engineering calculations.