Simulation Of 3D Turbulent Flows Research Articles

Розрахунок просторового турбулентного потоку в каналах авіаційних газотурбінних двигунів

This work is devoted to the development of approaches to the numerical simulation of 3D turbulent gas flows in different ducts of aircraft gas turbine engines, in particular in inlet device ducts. Inlet devices must provide large values of the total pressure recovery factor and flow uniformity at the engine compressor inlet. The aim of this work is the verification of the operability of a technique developed earlier for the calculation of the parameters of a 3D turbulent flow in complex-shape ducts. The basic approach is a numerical simulation of 3D turbulent gas flows on the basis of the complete averaged Navier¬–Stokes equations and a two-parameter turbulence model. The proposed technique of numerical simulation of a 3D gas flow was tested by calculating a 3D laminar flow in a square pipe bent at a right angle. The calculated flow pattern is in satisfactory agreement with the experimental data on the flow structure in a pipe elbow reported in the literature. Based on a numerical simulation of a 3D turbulent flow in the air duct of one of the air intake configurations for an aircraft turboprop engine, the efficiency of that configuration is assessed. The calculated flow parameter nonuniformity at the air intake outlet, i. e., at the compressor inlet, is compared with that obtained earlier for another air intake configuration for the same engine. It is pointed out that the air intake configuration considered earlier provides a much more uniform flow parameter distribution at the engine compressor inlet. On the whole, this work shows that the quality of subsonic air intakes for aircraft gas turbine engines can be assessed using the proposed numerical technique of 3D gas flow simulation. The results obtained may be used in the aerodynamic improvement of inlet devices for aircraft engines of different types.

Numerical simulation of 3D backward facing step flows at various Reynolds numbers

The work deals with the numerical simulation of 3D turbulent flow over backward facing step in a narrow channel. The mathematical model is based on the RANS equations with an explicit algebraic Reynolds stress model (EARSM). The numerical method uses implicit finite volume upwind discretization. While the eddy viscosity models fail in predicting complex 3D flows, the EARSM model is shown to provide results which agree well with experimental PIV data. The reference experimental data provide the 3D flow field. The simulations are compared with experiment for 3 values of Reynolds number.

Numerical Simulation of 3D Solid-Liquid Turbulent Flow in a Low Specific Speed Centrifugal Pump: Flow Field Analysis

For numerically simulating 3D solid-liquid turbulent flow in low specific speed centrifugal pumps, the iteration convergence problem caused by complex internal structure and high rotational speed of pump is always a problem for numeral simulation researchers. To solve this problem, the combination of three measures of dynamic underrelaxation factor adjustment, step method, and rotational velocity control means according to residual curves trends of operating parameters was used to improve the numerical convergence. Numeral simulation of 3D turbulent flow in a low specific speed solid-liquid centrifugal pump was performed, and the results showed that the improved solution strategy is greatly helpful to the numerical convergence. Moreover, the 3D turbulent flow fields in pumps have been simulated for the bottom ash-particles with the volume fraction of 10%, 20%, and 30% at the same particle diameter of 0.1 mm. The two-phase calculation results are compared with those of single-phase clean water flow. The calculated results gave the main region of the abrasion of the impeller and volute casing and improve the hydraulic design of the impeller in order to decrease the abrasion and increase the service life of the pump.

Multiobjective optimal design of runner blade using efficiency and draft tube pulsation criteria

In the present work new criteria of optimal design method for turbine runner [1] are proposed. Firstly, based on the efficient method which couples direct simulation of 3D turbulent flow and engineering semi empirical formulas, the combined method is built for hydraulic energy losses estimation in the whole turbine water passage and the efficiency criterion is formulated. Secondly, the criterion of dynamic loads minimization is developed for those caused by vortex rope precession downstream of the runner. This criterion is based on the finding that the monotonic increase of meridional velocity component in the direction to runner hub, downstream of its blades, provides for decreasing the intensity of vortex rope and thereafter, minimization of pressure pulsation amplitude. The developed algorithm was applied to optimal design of 640 MW Francis turbine runner. It can ensure high efficiency at best efficiency operating point as well as diminished pressure pulsations at full load regime.

Proper orthogonal decomposition closure models for turbulent flows: A numerical comparison

This paper puts forth two new closure models for the proper orthogonal decomposition reduced-order modeling of structurally dominated turbulent flows: the dynamic subgrid-scale model and the variational multiscale model. These models, which are considered state-of-the-art in large eddy simulation, together with the mixing length and the Smagorinsky closure models, are tested in the numerical simulation of 3D turbulent flow past a circular cylinder at Re=1000. Five criteria are used to judge the performance of the proper orthogonal decomposition reduced-order models: the kinetic energy spectrum, the mean velocity, the Reynolds stresses, the root mean square values of the velocity fluctuations, and the time evolution of the POD coefficients. All the numerical results are benchmarked against a direct numerical simulation. Based on these numerical results, we conclude that the dynamic subgrid-scale and the variational multiscale models are the most accurate.

Numerical simulation of 3D turbulent flow through an entire stage in a multistage centrifugal pump

A three-dimensional turbulent flow through a multistage centrifugal pump is numerically simulated using a commercial CFD software package. The simulation and analysis include flow fields in rotating impeller and stationary diffuser and is completed in a multiple reference frame. The standard k–ϵ turbulence model is applied. The analysis of the simulation reveals that the reverse flows exist in the zone near the impeller exit and diffuser entrance, resulting in asymmetric and unsteady flow field. There is a considerable interference on the velocity field at the impeller exit due to the interaction between impeller blades and diffuser vanes. The hydraulic performance is connected and evaluated with the 3D computational flow field. The current computation is verified by comparing predicted and measured head.