Numerical simulation of crisis phenomena in a subsonic air flow around a thick airfoil with vortex cells

Crisis phenomena arising in a subsonic air flow around a thick airfoil with vortex cells have been numerically simulated in the process of solving the nonstationary equations of mass and energy conservation and Reynolds equations closed by a model of shear-stress transfer with the use of the finite-volume factorization method. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 6, pp. 122–126, November–December, 2007.     

The resistance of a rotating diffuser to a gas flow

We examine the distribution of gas pressure in the case of convection diffusion in porous materials in the presence of centrifugal forces.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 16, No. 5, pp. 902–904, May, 1969.     

Numerical simulation of incompressible Navier-Stokes and Euler equations to the vortical flow about a delta wing

Summary An algorithm based on the method of artificial compressibility is used to solve the incompressible Navier-Stokes and Euler equations in 3D generalized curvilinear coordinates. The choice of the pseudocompressibility parameter is discussed and a function form of which accelerates the convergence effectively is presented. Numerical simulation of the vortical flow about a 70° delta wing is made by both Euler and Navier-Stokes methods. Comparison of the computed results and the experimental data indicates that the Euler method can capture the global flow feature, i.e., separation from the sharp leading edge and the formation of the leading-edge vortex; the Navier-Stokes method depicts not only the flow features captured by the Euler method, but also the boundary layer effects and specifically the secondary separation induced by the leading-edge vortex on the wing upper surface. Thus, the Navier-Stokes method shows a much improved correlation with the experimental data.     

Unsteady flow investigation in rotor-stator interface of a radial diffuser pump

The flow in a vaned diffuser radial pump is fully turbulent and strongly unsteady, caused by the rotor-stator interaction. In this paper, two-dimensional laser Doppler velocimetry (LDV) measurement results have been utilized to investigate the unsteady flow in a low specific speed radial diffuser pump with leaning impeller trailing edges. CFD simulations have been also conducted to provide more extensive results at different flow rates. The analysis has been mainly focused on the flow in the radial gap region between the impeller and diffuser where the unsteady interaction is the strongest. The velocity and turbulence fields are detailedly examined and quantitatively compared between CFD and LDV as well. In addition, the downstream effect from the impeller rotation has been compared between the leaning and normal trailing edges of the impeller.     

Influence of electrode commutation on magnetohydrodynamic flow in a supersonic diffuser

The slowing of an ionized gas in a supersonic diffuser operating as a magnetohydrodynamic (MHD) generator is investigated by numerical simulation. The calculation results, which reveal a significant dependence of the static pressure level and the Mach number distribution in the exit cross section of the diffuser on the design of the electrode system, are presented. Pis’ma Zh. Tekh. Fiz. 25, 1–8 (May 12, 1999)     

Immersed boundary simulation of flow through arterial junctions

The present work demonstrates implementation of a mass-conserving sharp-interface immersed boundary for simulation of flows in branched arterial geometries. A simplistic two-dimensional arterial junction is considered to capture the preliminary flow physics in the aortic regions. Numerical solutions are benchmarked against established available experimental PIV results in Ensley et al (Annu. Thorac. Surg. 68(4):1384–1390, 1999) and numerical predictions in Gilmanov and Sotiropoulos (J. Comput. Phys. 207(2):457–492, 2005) and de Zelicourt et al (Comput. Fluids 38(9):1749–1762, 2009). Simulations are further carried out for pulsated flows and effects of blockages near the junctions (due to stenosis or atherosclerosis). Instabilities in the flow structures near the junction and the resulting changes in the downstream pulsation frequency were observed. These changes account for the physiological heart defects that arise from the poorly working valve (due to blockage), giving rise to chest pain and breathing instability, and can potentially be used as a detection tool for arterial diseases.     

Unsteady compressible boundary layer swirling flow in a nozzle and a diffuser

This paper presents the results of the study of unsteady swirling boundary-layer flow of compressible fluid in a nozzle and a diffuser when the free stream velocity, mass transfer and wall temperature vary arbitrarily with time. The set of coupled nonlinear partial differential equations governing the flow which involves three independent variables has been solved numerically using an implicit finite-difference scheme. Both the heat transfer and skin friction are strongly affected by the free stream velocity, variation of the density-viscosity product across the boundary layer, mass transfer and swirl parameter. However, the variation of the wall temperature with time strongly affects only the heat transfer. Also, separationless flow along the entire length of the diffuser can be obtained by applying appropriate amount of suction.     

Analysis of the motion of a subsonic vapor flow in a quasi-closed volume

The motion of a vapor is described for the case in which the influence of geometry is isolated. The parameters are determined for a subsonic vapor flow on the outer boundary of a gas-kinetic layer near a surface of vaporization. Profiles of the gas-dynamic variables as a function of the dimensionless coordinate are calculated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 25, No. 3, pp. 460–466, September, 1973.     

Optimal control of diffuser shapes for non-uniform flow

A simplified model is used to identify the diffuser shape that maximises pressure recovery for several classes of non-uniform inflow. We find that optimal diffuser shapes strike a balance between not widening too soon, as this accentuates the non-uniform flow, and not staying narrow for too long, which is detrimental for wall drag. Three classes of non-uniform inflow are considered, with the axial velocity varying across the width of the diffuser entrance. The first case has inner and outer streams of different speeds, with a velocity jump between them that evolves into a shear layer downstream. The second case is a limiting case when these streams are of similar speed. The third case is a pure shear profile with linear velocity variation between the centre and outer edge of the diffuser. We describe the evolution of the time-averaged flow profile using a reduced mathematical model that has been previously tested against experiments and computational fluid dynamics models. The model consists of integrated mass and momentum equations, where wall drag is treated with a friction factor parameterisation. The governing equations of this model form the dynamics of an optimal control problem where the control is the diffuser channel shape. A numerical optimisation approach is used to solve the optimal control problem and Pontryagin’s maximum principle is used to find analytical solutions in the second and third cases. We show that some of the optimal diffuser shapes can be well approximated by piecewise linear sections. This suggests a low-dimensional parameterisation of the shapes, providing a structure in which more detailed and computationally expensive turbulence models can be used to find optimal shapes for more realistic flow behaviour.     

Film cooling effectiveness for subsonic slot injection into a cross flow

Summary A model is developed that allows the prediction of the film cooling effectiveness produced by slot injection into a uniform cross flow. The model relies on the fact that when the slot pressure exceeds the cross flow pressure by a small amount only so that injection is weak, the resulting small parameter may be exploited to solve the flow problem. The energy equation for the flow may then be solved to determine how much protection cold gas injection gives to the wall downstream of a slot. Although the leading order energy equation must be solved numerically, a simple asymptotic expression may also be derived to allow predictions of heat transfer at large distances from the injection slot.     

A dual-reciprocity method for acoustic radiation in a subsonic non-uniform flow

In this paper, the dual-reciprocity boundary-element method is used to model acoustic radiation in a subsonic non-uniform-flow field. The boundary-integral formulation is based on a direct boundary-integral equation developed very recently by the authors for acoustic radiation in a subsonic uniform flow. All the terms due to the non-uniform-flow effect are taken to the right-hand side and treated as source terms. The source terms result in a domain integral in the standard boundary-integral formulation. The dual-reciprocity method is then used to transform the resulting domain integral into boundary integrals. Numerical tests show reasonably good agreement with an analytical soution for a pulsating sphere submerged in a potential-flow field.     

Numerical computation of the thermal self-action effect in a subsonic gas flow

Results are obtained on the thermal self-action effect of an initially Gaussian beam in a subsonic weakly-absorbent gas flow in a broad range of similarity parameters.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 8, No. 1, pp. 35–42, January, 1990.     

A numerical study of incompressible Navier-Stokes flow through rectilinear and radial cascade of turbine blades

A numerical study is conducted to analyse the two-dimensional incompressible Navier-Stokes flows through the rectilinear and radial cascade of turbine blades. The flows are turbulent and their characteristics are relevant to those of the hydraulic turbines. For the rectilinear cascade, calculations have been made for a NACA 80 series turbine blade with various angles of attack. The outflow turning angle, force coefficients and static pressure distribution have been compared between the prediction and measurement with satisfactory agreements being obtained. The implications of flow turning angles on the total pressure loss are also discussed. The effects of grid distribution on the numerical predictions are also observed.     

Navier-Stokes analysis of vortex flow over a cropped delta wing

Summary The vortex flow over a 65° cropped delta wing with round leading edge, atM =0.85 and Re=2.38×10⁶, has been analyzed for 10°, 20°, and 30° angles of attack. A vertex based finite volume code, JUMBO3D, with an algebraic turbulence model has been used to solve the Reynolds Averaged Navier-Stokes (RANS) equations. An H–O type grid generated by a hybrid elliptic-algebraic method has been used here, and a significant improvement of the results over an O–O type grid has been obtained. The results are compared with available experimental data. The complex physical phenomena due to interactions among the primary, secondary, and tertiary vortices, cross-flow and terminating shocks, and turbulent boundary layer, as visualized from the numerical solutions obtained are presented and discussed here.     

Numerical simulation of viscous flow around a system of bodies on the basis of the Navier-Stokes equations in stream function-vorticity variables

A method of numerical solution of the Navier-Stokes equations in stream function-vortex-pressure variables is suggested to be used in simulating a nonstationary, nonsymmetric flow of a laminar incompressible viscous stream around a pair of rotating cylinders in a channel. Results of calculations which illustrate application of the method under different conditions of flow around bodies are presented. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 5, pp. 118–125, September–October, 2006.     

The Navier-Stokes solution for laminar flow past a semi-infinite flat plate

Summary A numerical solution joining Carrier and Lin's solution near the leading edge to the boundary layer solution at large distance of the leading edge is presented. The solution is valid for any Reynolds number. Results are given for the skin friction, the integrated skin friction, the displacement thickness, the pressure along the plate and the velocity ahead of the plate. The asymptotic value of the integrated skin friction agrees very well with the exact value. The displacement thickness is already different from zero for small distances ahead of the plate.     

Nonreciprocal effects in the double passage of light through a random diffuser and a birefringent crystal

We present a theoretical and experimental study of the scattering of light by double passage through a system that consists of a strong diffuser, a piece of birefringent crystal, and a plane mirror. We show that this arrangement can produce not only enhanced backscattering and satellite peaks but also satellite dips in the angular distribution of the mean intensity. The experiments are in agreement with theoretical results based on scalar diffraction theory in the paraxial approximation.     

Features of the breakup of jets of a low-viscosity liquid in a subsonic entraining flow of gas

The results of electrocontact measurements are used as a basis for examining the mechanisms (variants) of the breakup of a liquid jet and a dense atomizing jet. The deformational scheme of breakup in an entraining subsonic gas flow is generalized.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 60, No. 1, pp. 24–32, January, 1991.