Experimental flow analysis of three-dimensional separation zones in front of weirs

Some results of experimental studies are shown concerning subsonic flow in separation zones of three-dimensional turbulent boundary layers formed in front of cylindrical weirs and rectangular parallelepipeds or dashboards. The width to height ratio of the weirs was varied from 0.25 to 24, and the boundary layer thickness to weir height ratio at separation was varied from 0.2 to 2.0. Flow patterns are shown along with the effects of the setup ge-ometry, of the weir width to height ratio, of the boundary layer parameters, and of the Euler and Reynolds numbers on the flow pattern and on the coordinates of characteristic points in the separation zone. Data are furnished for determining the dimensions of three-dimensional separation zones in front of weirs. The flow and the heat transfer in three-dimensional separation zones at subsonic velocities have not yet been explored adequately. The separation data published in [1, 2, 3] are not sufficient for determining the flow pattern, the static pressure distribution, and the characteristic dimensions of a separation zone — all of which are needed for calculating the heat transfer in the separation zone [4].Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 50–54, January–February, 1972.The authors thank V. S. Avduevskii for reviewing the results.     

Investigation of the flow structure in nozzles with a throat section of constant height

The results of a theoretical and experimental investigation of the flow structure in plane nozzles with a throat section of constant height are presented. The effect of longitudinal and transverse deviations in the nozzle geometry on the transonic and supersonic flow parameters is studied.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 160–166, November–December, 1990.     

Natural Low-Frequency Riblets

A turbulent flow at modest Reynolds numbers (26,000–32,000, as defined in the text) over flat erodible sandy beds was investigated. The beds were composed of sand grains of uniform size with a diameter smaller than the viscous sublayer of the flow. When a modest sand transport (1.2 × 10-3–8.5 × 10-3 g/s·cm) was present, the near-wall coherent structures of the flow produced a bed form with a streaky longitudinal pattern. This pattern had a lateral spacing of about 100 viscous units and had less drag than a flat wall.The mechanism causing the drag reduction is due to a low-frequency riblet pattern which allows the flow to sustain higher wall shear stresses without additional erosion. That means during the riblet regime the sediment transport remains quasi-constant.The formation of the sand streaks as well as the drag reducing mechanism are discussed.     

Momentum produced by intense radiation falling on a surface

The transient flow produced in a stationary gas when an intense beam of radiation falls on a plane surface is studied. A flow pattern is proposed and approximate relations are derived for finding the momentum produced by sufficiently long irradiation of the body. The calculations are compared with available experimental data.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2. pp. 196–199. March–April, 1977.     

Longitudinal-transverse interaction in a three-dimensional boundary layer

Three-dimensional flow is considered for an incompressible fluid in a boundary layer developing along a curved solid surface during interaction between it and a small uneven area (projection or depression) on the surface. It is shown that an important part in the formation of the flow round the uneven area may be played by the drop in the pressure across the boundary layer. Conditions are formulated under which this effect, which is connected with the action of centrifugal forces, is realized. On the assumption that the longitudinal dimension of the uneven area is of the order of Re^–3/14, its width of the order of O(Re^–3/7), and its height O(Re^–4/7), where Re is the Reynolds number, asymptotic equations are derived which describe the motion of the fluid in the neighborhood of the uneven area.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 42–50, May–June, 1987.     

Experimental investigation of the flow in the separation zones of a turbulent boundary layer upstream from a two-dimensional step

The flow in the separation zones of a turbulent boundary layer upstream from a two-dimensional rectangular step has been experimentally investigated at subsonic flow velocities. The flow pattern and the static pressure distributions on the surface of the plate and the step are analyzed and the characteristic dimensions of the separation zones and the boundary-layer parameters in the separation section are determined.Moscow. Translated from Izvestiya Akademii Nauk SSSR. Mekhanika Zhidkosti i Gaza, No. 2, pp. 145–149, March–April, 1972.     

Boundary layer in the neighborhood of the intersection of a concave cylindrical surface and a plane

In studies devoted to the theoretical and experimental investigation of longitudinal flow of a viscous fluid past corner regions, a corner formed by the intersection of two planes is usually considered [1–3]. In contrast, the present paper is concerned with the flow in the neighborhood of the line of intersection of a plane and a concave cylindrical surface (see Fig. 1). The asymptotic behavior of the Navier-Stokes equations at large Re is investigated for such a flow. Estimates are obtained for the velocity and characteristic scales of the flow. It is shown that curvature of one of the surfaces qualitatively changes the pattern of the longitudinal flow of a viscous fluid past a corner. The development of a three-dimensional boundary layer on a plane in the domain of influence of a concave cylindrical surface is considered.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 160–165, March–April, 1981.     

Calculation of a supersonic overexpanded jet of an ideal gas issuing into an ambient transonic flow

The results of a numerical investigation of the exhaust of an inviscid axisymmetric jet into an ambient transonic flow in the overexpansion mode are presented. The steady-state flow pattern is obtained during a buildup process by integration of the nonsteady-state equations of gasdynamics using Godunov's finite-difference method.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 155–158, July–August, 1976.The authors are indebted to A. N. Kraiko and M. Ya. Ivanov for useful discussions and their interest in the work.     

Supersonic axisymmetric flow past a flat-ended cylinder in the wake of bodies of various shape

The pattern of the flow past a pair of bodies under conditions of direct and reverse flow restructuring is established and the aerodynamic and thermodynamic parameters at the surface of a flat-ended cylinder located in a supersonic wake are determined in relation to the leading body shape, drag, and permeability, and the distance between the bodies.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 6, pp. 125–132, November–December, 1996.     

Hydrodynamical modeling of the development of non-homogeneous oil reservoirs

Results of mathematical modeling of two-phase flow in non-homogeneous (layered) reservoirs are reported. Characteristic patterns of flow in reservoirs with high layer permeability contrast are investigated. It is shown that in such reservoirs crossflow between layers must be taken into account. Specific features of the use of hydrodynamic methods of improving oil recovery in such reservoirs based upon flow pattern control are studied. The possibility of using rational flow management to improve oil recovery partially blocking the reservoir in the neighborhood of the wells is demonstrated.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 6, pp. 87–94, November–December, 1995.     

Behaviors of flow mechanisms and heat transfer of non-Newtonian fluids through a spinneret

This investigation examines non-Newtonian flow mechanisms and heat transfer characteristics for a micro spinneret. The working fluid, Polyethylene terephthalate (PET), is the raw material of micro fiber, and a large-scale experimental test model was designed to visualize the complex viscous flow system in the micro spinneret. To visualize the complex convective flow system, an experimental test model was constructed, using glycerin instead of PET. The related parameters of PET were compared with those of glycerin. The power law correlates the shear strain with PET viscosity at various temperatures. The pressure distribution along the flow direction was measured and the flow pattern was visualized using polyethylene (PE) powder of 20–40 m. Similar configurations were calculated for micro spinneret physical parameters to determine the thermal flow characteristics. The Reynolds number in the test model is not less than 10^–2. In the non-Newtonian PET working fluid of practical micro spinneret, flows with Re = 10⁴ to 10^–2 are in the same low Reynolds number flow regime. Therefore, the working fluid is expected to have the same flow characteristic. A numerical solution covering the range of approximately Re = 10^–4 at PET confirms that the flow characteristics of glycerin are constant for Re = 1.228 × 10^–2. The Peclet number in the test model can be adjusted to a value similar to that in the micro spinneret. The flow visualization was compared with that of the numerical solution, and the friction factor and Nusselt number in the micro spinneret were analyzed. Finally, numerical results and friction factor with various exit angles of micro spinneret in a triangular zone flow system were also summarized.     

Supersonic boundary layer transition induced by roughness on the attachment line of a yawed cylinder

The effect of a single two-dimensional irregularity and sandy roughness on boundary layer transition in supersonic flow over a yawed cylinder (M = 6)-has been experimentally investigated. The characteristic flow regimes beyond the roughness are identified, and their limits are determined as a function of the Reynolds number and the ratio of the height of the roughness to the characteristic thickness of the boundary layer. A qualitative comparison is made with the flow regimes induced by roughness on the attachment line in incompressible flow over a cylinder [1–3]. The thermal indicator coating method is used to measure the heat fluxes along the attachment line and a comparison is made with calculations carried out in accordance with the methods of other authors.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 28–35, November–December, 1991.The authors are grateful to A. F. Kiselev for helping to calculate the heat flux in the turbulent boundary layer.     

Supersonic two-dimensional flow in a forward separation zone

Supersonic separated flow past a spiked body with a plane cap on the end of the spike (a flat plate or a wedge) is studied. The cases of both symmetric and nonsymmetric flow, with a rotating or nonrotating spike, are considered. The flow pattern, visualized by means of a Toepler instrument and a laser knife, and the limiting streamline patterns are analyzed. The reasons for the initiation of self-oscillations in the flow between the cap and the body are determined. The flow patterns for a rotating and nonrotating spike are compared.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 152–162, January–February, 1995.     

Numerical investigation of heat and mass transfer processes accompanying crystallization under conditions when body forces produce weak accelerations

A numerical investigation has been made into the development of the flow of a liquid and distribution of an dopant during crystallization under conditions when weak body forces act. It is shown that the development and structure of the flow, and also the distribution of the dopant over the height of the liquid volume and along the radius near the crystallization boundary are influenced by the thermal boundary conditions and the wettability of the ampoule wall by the liquid. The mean (over the height of the ampoule) radial inhomogeneity of the dopant distribution is found as a function of the time and the regime parameters (the Grashof, Marangoni, and Schmidt numbers).Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 186–192, January–February, 1981.     

Transverse subsonic flow past a cylinder

At around the critical Reynolds number Re = (1.5–4.0)·10⁵ there is an abrupt change in the pattern of transverse subsonic flow past a circular cylinder, and the drag coefficient C_x decreases sharply [1]. A large body of both experimental and computational investigations has now been made into subsonic flow past a cylinder [1–4]. A significant contribution to a deeper understanding of the phenomenon was made by [4], which gives a physical interpretation of a number of theoretical and experimental results obtained in a wide range of Re. Nevertheless, the complicated nonstationary nature of flow past a cylinder with separation and the occurrence of three-dimensional flows when two-dimensional flow is simulated in wind tunnels do not permit one to regard the problem as fully studied. The aim of the present work was to make additional experimental investigations into transverse subsonic flow past a cylinder and, in particular, to study the possible asymmetric stable flow regimes near the critical Reynolds number.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 154–157, March–April, 1980.     

Sudden Blocking of a Subcritical Open–Channel Flow

This paper reports results of experiments in which a steady nonuniform flow in a rectangular channel with an even horizontal bottom was blocked by a rapidly falling shield. Data on the height of the splash–up of water on the shield and the shape, propagation speed, height, and internal structure of the upstream propagating wave of the bore type are obtained for various liquid flow rates at the channel entrance. It is established that the bore produces a strong stratification in the liquid particle velocity, and under particular conditions, the speed of propagation and height of the bore, and the height of the water splash–up on the wall are constant and are determined only by the critical depth for unperturbed flow, i.e., by the specified flow rate.     

Hydrodynamics of a sphere in a stratified fluid

The flow pattern around a sphere moving at constant velocity in a fluid with an exponential density distribution is investigated by optical methods. The thin density boundary layer forming the high-gradient envelope of the wake is distinguished as one of the elements of the structure. The symmetry properties of the flow are investigated. The limits of applicability of the traditional approximation of weak stratification in the problem of excitation of attached internal waves are noted.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 3–9, January–February, 1989.     

Semiempirical method of calculating overexpanded turbulent separated flow in a conical laval nozzle

A mathematical model of separated nozzle flow is developed. The model takes into account the effect of the boundary layer and the pressure variation over the entire separation zone inside the nozzle. The effect of the geometric and gas dynamic factors on the separated flow pattern is investigated numerically.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 60–66, November–December, 1988.     

Investigation of the propagation of a two-dimensional wall jet over a step

The propagation of an underexpanded sonic jet over a flat end face has been experimentally investigated. As distinct from previous studies, the object of investigation is not a free jet, but a jet flowing from a nozzle along a horizontal surface. The total separation of the jet from the surface and its attachment to the end wall are related to the propagation characteristics of underexpanded wall jets. The effect of the total pressure in the jet and the height of the step on the separation of the jet and its attachment to the wall and, moreover, on the principal characteristics of the flow — the pressure in the base region, the extent of the circulation zone, the jet trajectory — is examined. The associated hysteresis effects are studied.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 61–66, July–August, 1991.     

Flow past blunt bodies with nose spikes and surface injection

Axisymmetric supersonic ideal-gas flow past a blunt body with a forward-projecting spike is numerically investigated with allowance for injection from the surface. The effect of the length and shape of the spike, the parameters of the injected gas and the position of the permeable zone on the flow pattern and drag is studied.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 128–133, July–August, 1987.