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This paper presents the results of liquid-fuel model combustor calculations based on different numerical approaches to the development of a verified simulation method of combustor operation. Both steady and transient studies were carried using various RANS turbulent models and the detached eddy simulation (DES) method. The results of these studies were compared with experimental data obtained by optical methods. The largest differences between experiment and calculations are observed for the near-axial flow field where recirculation backflow is formed. This vortex structure can be properly resolved in a DES simulation and in transient calculations based on the SAS SST model. The use of the above-mentioned approaches in combination with the flamelet combustion model provides maximum accuracy in predicting the parameters of reacting swirling flow, in particular the velocity and temperature distributions in the combustor. [ABSTRACT FROM AUTHOR]

A system of the Euler equations that describe two-dimensional steady flows of an ideal fluid is considered. This system is reduced to a nonlinear Laplace equation for the stream function. With the use of the Hirota -function, solutions of three elliptical equations (sin-Gordon, sinh-Gordon, and Tzitzeica equations) are found. A simple method of deriving solutions in the form of rational expressions in elliptical functions is proposed. The resultant solutions describe sources in a swirled fluid, jet flows, chains of sources and sinks, and vortex structures. It is shown that the fluid flux through a closed curve is quantized in the case of the elliptical sin-Gordon equation. [ABSTRACT FROM AUTHOR]

Investigation of hydro-turbine runner flow on a full-scale test rig consisting of a spiral casing, a stator, guide vanes, and a runner is difficult due to high cost and labor intensity. Therefore, an approach to modeling the inlet velocity profile of a hydro turbine draft tube is proposed that significantly reduces the cost of testing. In this approach, the draft tube inlet flow is modeled using a special swirl apparatus which is a combination of two swirlers: fixed and rotating. The paper presents the results of analytical calculation of the vane shape that provides a given velocity distribution corresponding to the optimal operation of the hydro turbine. [ABSTRACT FROM AUTHOR]

This paper deals with a laminar swirling flow of a viscous fluid over a stretchable rotating disk. The classical flow over a solid disk is known as the Kármán flow problem. For the first time in the literature, the combined effects of both the Coriolis force and radial stretching on the stability of the Kármán swirling flow has been carried out. The numerical investigation has been performed by using the Chebyshev spectral method. It is discovered that surface stretching produces a destabilising effect on the Kármán flow. [ABSTRACT FROM AUTHOR]

The aerodynamics of a laboratory model of an improved four-vortex coal combustion furnace is studied using laser Doppler anemometry. For the isothermal case, the distributions of the averaged velocity and velocity pulsations are obtained for various flow regimes. The main features of the flow are established. The experimental results are compared with previous particle image velocimetry measurements, showing good agreement. [ABSTRACT FROM AUTHOR]

This paper describes the results of experimental studies of a flow using the prototype of a propeller-type microhydraulic turbine. The tests are carried out on a testbed in which atmospheric air is used as a working medium. The measurements carried out with the help of a two-component laser-Doppler anemometer are used to obtain velocity distributions behind a runner in the case where the operating modes of the device change in a wide range. It is shown that the created model microhydraulic turbine has optimal parameters for the conditions set during the design, and a change in the operating mode of the device from nominal parameters to underload or overload increases the residual swirl of the flow and the generation of strong hydrodynamic instability in the form of a precessing vortex rope. In this case, axial velocity over the cross section is distributed unevenly and the flow pulsation level is increased. [ABSTRACT FROM AUTHOR]

The flow in a Ranque tube with a square cross-section channel has been studied using the hydraulic concept of strongly swirling flow with a circulation zone. Based on experimental data, it has been found that for flow in a vortex tube, the hydraulic condition of flow crisis is satisfied: the longitudinal velocity becomes equal to the velocity of propagation of centrifugal waves at the boundary between the vortex and the circulation zone. It has been shown that the temperature variation along the flow occurs mainly in the region of the working channel in which the ratio of the longitudinal velocity at the vortex boundary to the propagation velocity of centrifugal waves fluctuates about unity. The existence of a previously unknown energy separation mechanism due to the presence of hydraulic jumps in the development of internal waves in a Ranque tube was assumed. [ABSTRACT FROM AUTHOR]

A swirling flow in a tangential-type hydrodynamic chamber with stationary vortex structures is experimentally investigated. The main attention is paid to determining the geometric and kinematic parameters necessary for a correct description of helical vortices and their spatial structure, in particular, to testing the possibility of a theoretical description of the limiting case where the vortex becomes stationary, i.e., its rotation frequency (or precession frequency) vanishes. It is shown that the theory of helical vortices ensures a sufficiently accurate prediction of conditions for the appearance of their stationary (motionless) states. [ABSTRACT FROM AUTHOR]

This paper presents the results of experimental studies of the spatial flow structure and coherent structures in the initial region of swirling jets at a Reynolds number of 5000 and different swirl rates. The contribution of these structures to the turbulent transport of momentum and mass was first quantitatively evaluated. In addition, for the case of high swirl with vortex core breakdown, the effect of coherent structures on the fluctuation in the local heat release rate due to the deformation of the flame front was investigated for combustion of a methane-air mixtures with an air excess ratio of 1.43. [ABSTRACT FROM AUTHOR]

An axisymmetric laminar swirling jet of a viscous incompressible fluid flowing from a rotating semi-infinite tube in space filled with the same fluid is explored. The inner surface of the tube rotates with a constant angular velocity, and the outer surface is stationary or rotates with the same angular velocity. It is shown that in the first case, the flow field far from the tube orifice is described by the Loitsyansky asymptotic solution, and in the second case (with weak coflow), it is described by the Long-Gol'dshtik-Zubtsov self-similar solution. The Gol'dshtik hidden invariant is generalized to arbitrary axisymmetric swirling jets, and its influence on the jet asymptotics is studied. Strongly swirling jets are calculated, and the dependence of the parameters of the recirculation zone (vortex breakdown in a swirling jet) on the swirl number and the Reynolds number is examined. [ABSTRACT FROM AUTHOR]

A possibility of using the 4D Qflow protocol, which is commonly applied for medical diagnostics by magnetic resonance imaging, for determining the structure of the three-dimensional fluid flow in the human blood circulation system is considered. Specialized software is developed for processing DICOM images taken by a magnetic resonance scanner, and the retrieved unsteady three-dimensional velocity field is analyzed. It is demonstrated that magnetic resonance measurements allow one to detect the existence of the swirling flow in blood vessel models and also to study the degree of its swirling (helicity) both qualitatively and quantitatively. [ABSTRACT FROM AUTHOR]